Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * procarray.c
4 : : * POSTGRES process array code.
5 : : *
6 : : *
7 : : * This module maintains arrays of PGPROC substructures, as well as associated
8 : : * arrays in ProcGlobal, for all active backends. Although there are several
9 : : * uses for this, the principal one is as a means of determining the set of
10 : : * currently running transactions.
11 : : *
12 : : * Because of various subtle race conditions it is critical that a backend
13 : : * hold the correct locks while setting or clearing its xid (in
14 : : * ProcGlobal->xids[]/MyProc->xid). See notes in
15 : : * src/backend/access/transam/README.
16 : : *
17 : : * The process arrays now also include structures representing prepared
18 : : * transactions. The xid and subxids fields of these are valid, as are the
19 : : * myProcLocks lists. They can be distinguished from regular backend PGPROCs
20 : : * at need by checking for pid == 0.
21 : : *
22 : : * During hot standby, we also keep a list of XIDs representing transactions
23 : : * that are known to be running on the primary (or more precisely, were running
24 : : * as of the current point in the WAL stream). This list is kept in the
25 : : * KnownAssignedXids array, and is updated by watching the sequence of
26 : : * arriving XIDs. This is necessary because if we leave those XIDs out of
27 : : * snapshots taken for standby queries, then they will appear to be already
28 : : * complete, leading to MVCC failures. Note that in hot standby, the PGPROC
29 : : * array represents standby processes, which by definition are not running
30 : : * transactions that have XIDs.
31 : : *
32 : : * It is perhaps possible for a backend on the primary to terminate without
33 : : * writing an abort record for its transaction. While that shouldn't really
34 : : * happen, it would tie up KnownAssignedXids indefinitely, so we protect
35 : : * ourselves by pruning the array when a valid list of running XIDs arrives.
36 : : *
37 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
38 : : * Portions Copyright (c) 1994, Regents of the University of California
39 : : *
40 : : *
41 : : * IDENTIFICATION
42 : : * src/backend/storage/ipc/procarray.c
43 : : *
44 : : *-------------------------------------------------------------------------
45 : : */
46 : : #include "postgres.h"
47 : :
48 : : #include <signal.h>
49 : :
50 : : #include "access/subtrans.h"
51 : : #include "access/transam.h"
52 : : #include "access/twophase.h"
53 : : #include "access/xact.h"
54 : : #include "access/xlogutils.h"
55 : : #include "catalog/catalog.h"
56 : : #include "catalog/pg_authid.h"
57 : : #include "miscadmin.h"
58 : : #include "pgstat.h"
59 : : #include "postmaster/bgworker.h"
60 : : #include "port/pg_lfind.h"
61 : : #include "storage/proc.h"
62 : : #include "storage/procarray.h"
63 : : #include "storage/procsignal.h"
64 : : #include "utils/acl.h"
65 : : #include "utils/builtins.h"
66 : : #include "utils/injection_point.h"
67 : : #include "utils/lsyscache.h"
68 : : #include "utils/rel.h"
69 : : #include "utils/snapmgr.h"
70 : : #include "utils/wait_event.h"
71 : :
72 : : #define UINT32_ACCESS_ONCE(var) ((uint32)(*((volatile uint32 *)&(var))))
73 : :
74 : : /* Our shared memory area */
75 : : typedef struct ProcArrayStruct
76 : : {
77 : : int numProcs; /* number of valid procs entries */
78 : : int maxProcs; /* allocated size of procs array */
79 : :
80 : : /*
81 : : * Known assigned XIDs handling
82 : : */
83 : : int maxKnownAssignedXids; /* allocated size of array */
84 : : int numKnownAssignedXids; /* current # of valid entries */
85 : : int tailKnownAssignedXids; /* index of oldest valid element */
86 : : int headKnownAssignedXids; /* index of newest element, + 1 */
87 : :
88 : : /*
89 : : * Highest subxid that has been removed from KnownAssignedXids array to
90 : : * prevent overflow; or InvalidTransactionId if none. We track this for
91 : : * similar reasons to tracking overflowing cached subxids in PGPROC
92 : : * entries. Must hold exclusive ProcArrayLock to change this, and shared
93 : : * lock to read it.
94 : : */
95 : : TransactionId lastOverflowedXid;
96 : :
97 : : /* oldest xmin of any replication slot */
98 : : TransactionId replication_slot_xmin;
99 : : /* oldest catalog xmin of any replication slot */
100 : : TransactionId replication_slot_catalog_xmin;
101 : :
102 : : /* indexes into allProcs[], has PROCARRAY_MAXPROCS entries */
103 : : int pgprocnos[FLEXIBLE_ARRAY_MEMBER];
104 : : } ProcArrayStruct;
105 : :
106 : : /*
107 : : * State for the GlobalVisTest* family of functions. Those functions can
108 : : * e.g. be used to decide if a deleted row can be removed without violating
109 : : * MVCC semantics: If the deleted row's xmax is not considered to be running
110 : : * by anyone, the row can be removed.
111 : : *
112 : : * To avoid slowing down GetSnapshotData(), we don't calculate a precise
113 : : * cutoff XID while building a snapshot (looking at the frequently changing
114 : : * xmins scales badly). Instead we compute two boundaries while building the
115 : : * snapshot:
116 : : *
117 : : * 1) definitely_needed, indicating that rows deleted by XIDs >=
118 : : * definitely_needed are definitely still visible.
119 : : *
120 : : * 2) maybe_needed, indicating that rows deleted by XIDs < maybe_needed can
121 : : * definitely be removed
122 : : *
123 : : * When testing an XID that falls in between the two (i.e. XID >= maybe_needed
124 : : * && XID < definitely_needed), the boundaries can be recomputed (using
125 : : * ComputeXidHorizons()) to get a more accurate answer. This is cheaper than
126 : : * maintaining an accurate value all the time.
127 : : *
128 : : * As it is not cheap to compute accurate boundaries, we limit the number of
129 : : * times that happens in short succession. See GlobalVisTestShouldUpdate().
130 : : *
131 : : *
132 : : * There are three backend lifetime instances of this struct, optimized for
133 : : * different types of relations. As e.g. a normal user defined table in one
134 : : * database is inaccessible to backends connected to another database, a test
135 : : * specific to a relation can be more aggressive than a test for a shared
136 : : * relation. Currently we track four different states:
137 : : *
138 : : * 1) GlobalVisSharedRels, which only considers an XID's
139 : : * effects visible-to-everyone if neither snapshots in any database, nor a
140 : : * replication slot's xmin, nor a replication slot's catalog_xmin might
141 : : * still consider XID as running.
142 : : *
143 : : * 2) GlobalVisCatalogRels, which only considers an XID's
144 : : * effects visible-to-everyone if neither snapshots in the current
145 : : * database, nor a replication slot's xmin, nor a replication slot's
146 : : * catalog_xmin might still consider XID as running.
147 : : *
148 : : * I.e. the difference to GlobalVisSharedRels is that
149 : : * snapshot in other databases are ignored.
150 : : *
151 : : * 3) GlobalVisDataRels, which only considers an XID's
152 : : * effects visible-to-everyone if neither snapshots in the current
153 : : * database, nor a replication slot's xmin consider XID as running.
154 : : *
155 : : * I.e. the difference to GlobalVisCatalogRels is that
156 : : * replication slot's catalog_xmin is not taken into account.
157 : : *
158 : : * 4) GlobalVisTempRels, which only considers the current session, as temp
159 : : * tables are not visible to other sessions.
160 : : *
161 : : * GlobalVisTestFor(relation) returns the appropriate state
162 : : * for the relation.
163 : : *
164 : : * The boundaries are FullTransactionIds instead of TransactionIds to avoid
165 : : * wraparound dangers. There e.g. would otherwise exist no procarray state to
166 : : * prevent maybe_needed to become old enough after the GetSnapshotData()
167 : : * call.
168 : : *
169 : : * The typedef is in the header.
170 : : */
171 : : struct GlobalVisState
172 : : {
173 : : /* XIDs >= are considered running by some backend */
174 : : FullTransactionId definitely_needed;
175 : :
176 : : /* XIDs < are not considered to be running by any backend */
177 : : FullTransactionId maybe_needed;
178 : : };
179 : :
180 : : /*
181 : : * Result of ComputeXidHorizons().
182 : : */
183 : : typedef struct ComputeXidHorizonsResult
184 : : {
185 : : /*
186 : : * The value of TransamVariables->latestCompletedXid when
187 : : * ComputeXidHorizons() held ProcArrayLock.
188 : : */
189 : : FullTransactionId latest_completed;
190 : :
191 : : /*
192 : : * The same for procArray->replication_slot_xmin and
193 : : * procArray->replication_slot_catalog_xmin.
194 : : */
195 : : TransactionId slot_xmin;
196 : : TransactionId slot_catalog_xmin;
197 : :
198 : : /*
199 : : * Oldest xid that any backend might still consider running. This needs to
200 : : * include processes running VACUUM, in contrast to the normal visibility
201 : : * cutoffs, as vacuum needs to be able to perform pg_subtrans lookups when
202 : : * determining visibility, but doesn't care about rows above its xmin to
203 : : * be removed.
204 : : *
205 : : * This likely should only be needed to determine whether pg_subtrans can
206 : : * be truncated. It currently includes the effects of replication slots,
207 : : * for historical reasons. But that could likely be changed.
208 : : */
209 : : TransactionId oldest_considered_running;
210 : :
211 : : /*
212 : : * Oldest xid for which deleted tuples need to be retained in shared
213 : : * tables.
214 : : *
215 : : * This includes the effects of replication slots. If that's not desired,
216 : : * look at shared_oldest_nonremovable_raw;
217 : : */
218 : : TransactionId shared_oldest_nonremovable;
219 : :
220 : : /*
221 : : * Oldest xid that may be necessary to retain in shared tables. This is
222 : : * the same as shared_oldest_nonremovable, except that is not affected by
223 : : * replication slot's catalog_xmin.
224 : : *
225 : : * This is mainly useful to be able to send the catalog_xmin to upstream
226 : : * streaming replication servers via hot_standby_feedback, so they can
227 : : * apply the limit only when accessing catalog tables.
228 : : */
229 : : TransactionId shared_oldest_nonremovable_raw;
230 : :
231 : : /*
232 : : * Oldest xid for which deleted tuples need to be retained in non-shared
233 : : * catalog tables.
234 : : */
235 : : TransactionId catalog_oldest_nonremovable;
236 : :
237 : : /*
238 : : * Oldest xid for which deleted tuples need to be retained in normal user
239 : : * defined tables.
240 : : */
241 : : TransactionId data_oldest_nonremovable;
242 : :
243 : : /*
244 : : * Oldest xid for which deleted tuples need to be retained in this
245 : : * session's temporary tables.
246 : : */
247 : : TransactionId temp_oldest_nonremovable;
248 : : } ComputeXidHorizonsResult;
249 : :
250 : : /*
251 : : * Return value for GlobalVisHorizonKindForRel().
252 : : */
253 : : typedef enum GlobalVisHorizonKind
254 : : {
255 : : VISHORIZON_SHARED,
256 : : VISHORIZON_CATALOG,
257 : : VISHORIZON_DATA,
258 : : VISHORIZON_TEMP,
259 : : } GlobalVisHorizonKind;
260 : :
261 : : /*
262 : : * Reason codes for KnownAssignedXidsCompress().
263 : : */
264 : : typedef enum KAXCompressReason
265 : : {
266 : : KAX_NO_SPACE, /* need to free up space at array end */
267 : : KAX_PRUNE, /* we just pruned old entries */
268 : : KAX_TRANSACTION_END, /* we just committed/removed some XIDs */
269 : : KAX_STARTUP_PROCESS_IDLE, /* startup process is about to sleep */
270 : : } KAXCompressReason;
271 : :
272 : :
273 : : static ProcArrayStruct *procArray;
274 : :
275 : : static PGPROC *allProcs;
276 : :
277 : : /*
278 : : * Cache to reduce overhead of repeated calls to TransactionIdIsInProgress()
279 : : */
280 : : static TransactionId cachedXidIsNotInProgress = InvalidTransactionId;
281 : :
282 : : /*
283 : : * Bookkeeping for tracking emulated transactions in recovery
284 : : */
285 : : static TransactionId *KnownAssignedXids;
286 : : static bool *KnownAssignedXidsValid;
287 : : static TransactionId latestObservedXid = InvalidTransactionId;
288 : :
289 : : /*
290 : : * If we're in STANDBY_SNAPSHOT_PENDING state, standbySnapshotPendingXmin is
291 : : * the highest xid that might still be running that we don't have in
292 : : * KnownAssignedXids.
293 : : */
294 : : static TransactionId standbySnapshotPendingXmin;
295 : :
296 : : /*
297 : : * State for visibility checks on different types of relations. See struct
298 : : * GlobalVisState for details. As shared, catalog, normal and temporary
299 : : * relations can have different horizons, one such state exists for each.
300 : : */
301 : : static GlobalVisState GlobalVisSharedRels;
302 : : static GlobalVisState GlobalVisCatalogRels;
303 : : static GlobalVisState GlobalVisDataRels;
304 : : static GlobalVisState GlobalVisTempRels;
305 : :
306 : : /*
307 : : * This backend's RecentXmin at the last time the accurate xmin horizon was
308 : : * recomputed, or InvalidTransactionId if it has not. Used to limit how many
309 : : * times accurate horizons are recomputed. See GlobalVisTestShouldUpdate().
310 : : */
311 : : static TransactionId ComputeXidHorizonsResultLastXmin;
312 : :
313 : : #ifdef XIDCACHE_DEBUG
314 : :
315 : : /* counters for XidCache measurement */
316 : : static long xc_by_recent_xmin = 0;
317 : : static long xc_by_known_xact = 0;
318 : : static long xc_by_my_xact = 0;
319 : : static long xc_by_latest_xid = 0;
320 : : static long xc_by_main_xid = 0;
321 : : static long xc_by_child_xid = 0;
322 : : static long xc_by_known_assigned = 0;
323 : : static long xc_no_overflow = 0;
324 : : static long xc_slow_answer = 0;
325 : :
326 : : #define xc_by_recent_xmin_inc() (xc_by_recent_xmin++)
327 : : #define xc_by_known_xact_inc() (xc_by_known_xact++)
328 : : #define xc_by_my_xact_inc() (xc_by_my_xact++)
329 : : #define xc_by_latest_xid_inc() (xc_by_latest_xid++)
330 : : #define xc_by_main_xid_inc() (xc_by_main_xid++)
331 : : #define xc_by_child_xid_inc() (xc_by_child_xid++)
332 : : #define xc_by_known_assigned_inc() (xc_by_known_assigned++)
333 : : #define xc_no_overflow_inc() (xc_no_overflow++)
334 : : #define xc_slow_answer_inc() (xc_slow_answer++)
335 : :
336 : : static void DisplayXidCache(void);
337 : : #else /* !XIDCACHE_DEBUG */
338 : :
339 : : #define xc_by_recent_xmin_inc() ((void) 0)
340 : : #define xc_by_known_xact_inc() ((void) 0)
341 : : #define xc_by_my_xact_inc() ((void) 0)
342 : : #define xc_by_latest_xid_inc() ((void) 0)
343 : : #define xc_by_main_xid_inc() ((void) 0)
344 : : #define xc_by_child_xid_inc() ((void) 0)
345 : : #define xc_by_known_assigned_inc() ((void) 0)
346 : : #define xc_no_overflow_inc() ((void) 0)
347 : : #define xc_slow_answer_inc() ((void) 0)
348 : : #endif /* XIDCACHE_DEBUG */
349 : :
350 : : /* Primitives for KnownAssignedXids array handling for standby */
351 : : static void KnownAssignedXidsCompress(KAXCompressReason reason, bool haveLock);
352 : : static void KnownAssignedXidsAdd(TransactionId from_xid, TransactionId to_xid,
353 : : bool exclusive_lock);
354 : : static bool KnownAssignedXidsSearch(TransactionId xid, bool remove);
355 : : static bool KnownAssignedXidExists(TransactionId xid);
356 : : static void KnownAssignedXidsRemove(TransactionId xid);
357 : : static void KnownAssignedXidsRemoveTree(TransactionId xid, int nsubxids,
358 : : TransactionId *subxids);
359 : : static void KnownAssignedXidsRemovePreceding(TransactionId removeXid);
360 : : static int KnownAssignedXidsGet(TransactionId *xarray, TransactionId xmax);
361 : : static int KnownAssignedXidsGetAndSetXmin(TransactionId *xarray,
362 : : TransactionId *xmin,
363 : : TransactionId xmax);
364 : : static TransactionId KnownAssignedXidsGetOldestXmin(void);
365 : : static void KnownAssignedXidsDisplay(int trace_level);
366 : : static void KnownAssignedXidsReset(void);
367 : : static inline void ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid);
368 : : static void ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid);
369 : : static void MaintainLatestCompletedXid(TransactionId latestXid);
370 : : static void MaintainLatestCompletedXidRecovery(TransactionId latestXid);
371 : :
372 : : static inline FullTransactionId FullXidRelativeTo(FullTransactionId rel,
373 : : TransactionId xid);
374 : : static void GlobalVisUpdateApply(ComputeXidHorizonsResult *horizons);
375 : :
376 : : /*
377 : : * Report shared-memory space needed by ProcArrayShmemInit
378 : : */
379 : : Size
7576 tgl@sss.pgh.pa.us 380 :CBC 2147 : ProcArrayShmemSize(void)
381 : : {
382 : : Size size;
383 : :
384 : : /* Size of the ProcArray structure itself */
385 : : #define PROCARRAY_MAXPROCS (MaxBackends + max_prepared_xacts)
386 : :
5224 rhaas@postgresql.org 387 : 2147 : size = offsetof(ProcArrayStruct, pgprocnos);
1433 388 : 2147 : size = add_size(size, mul_size(sizeof(int), PROCARRAY_MAXPROCS));
389 : :
390 : : /*
391 : : * During Hot Standby processing we have a data structure called
392 : : * KnownAssignedXids, created in shared memory. Local data structures are
393 : : * also created in various backends during GetSnapshotData(),
394 : : * TransactionIdIsInProgress() and GetRunningTransactionData(). All of the
395 : : * main structures created in those functions must be identically sized,
396 : : * since we may at times copy the whole of the data structures around. We
397 : : * refer to this size as TOTAL_MAX_CACHED_SUBXIDS.
398 : : *
399 : : * Ideally we'd only create this structure if we were actually doing hot
400 : : * standby in the current run, but we don't know that yet at the time
401 : : * shared memory is being set up.
402 : : */
403 : : #define TOTAL_MAX_CACHED_SUBXIDS \
404 : : ((PGPROC_MAX_CACHED_SUBXIDS + 1) * PROCARRAY_MAXPROCS)
405 : :
5799 tgl@sss.pgh.pa.us 406 [ + + ]: 2147 : if (EnableHotStandby)
407 : : {
5800 408 : 2135 : size = add_size(size,
409 : : mul_size(sizeof(TransactionId),
410 : 2135 : TOTAL_MAX_CACHED_SUBXIDS));
5902 411 : 2135 : size = add_size(size,
5800 412 : 2135 : mul_size(sizeof(bool), TOTAL_MAX_CACHED_SUBXIDS));
413 : : }
414 : :
7512 415 : 2147 : return size;
416 : : }
417 : :
418 : : /*
419 : : * Initialize the shared PGPROC array during postmaster startup.
420 : : */
421 : : void
563 heikki.linnakangas@i 422 : 1150 : ProcArrayShmemInit(void)
423 : : {
424 : : bool found;
425 : :
426 : : /* Create or attach to the ProcArray shared structure */
7605 tgl@sss.pgh.pa.us 427 : 1150 : procArray = (ProcArrayStruct *)
5930 simon@2ndQuadrant.co 428 : 1150 : ShmemInitStruct("Proc Array",
429 : : add_size(offsetof(ProcArrayStruct, pgprocnos),
430 : : mul_size(sizeof(int),
1433 rhaas@postgresql.org 431 : 1150 : PROCARRAY_MAXPROCS)),
432 : : &found);
433 : :
7605 tgl@sss.pgh.pa.us 434 [ + - ]: 1150 : if (!found)
435 : : {
436 : : /*
437 : : * We're the first - initialize.
438 : : */
439 : 1150 : procArray->numProcs = 0;
1433 rhaas@postgresql.org 440 : 1150 : procArray->maxProcs = PROCARRAY_MAXPROCS;
5902 tgl@sss.pgh.pa.us 441 : 1150 : procArray->maxKnownAssignedXids = TOTAL_MAX_CACHED_SUBXIDS;
5800 442 : 1150 : procArray->numKnownAssignedXids = 0;
443 : 1150 : procArray->tailKnownAssignedXids = 0;
444 : 1150 : procArray->headKnownAssignedXids = 0;
5902 445 : 1150 : procArray->lastOverflowedXid = InvalidTransactionId;
3134 peter_e@gmx.net 446 : 1150 : procArray->replication_slot_xmin = InvalidTransactionId;
447 : 1150 : procArray->replication_slot_catalog_xmin = InvalidTransactionId;
828 heikki.linnakangas@i 448 : 1150 : TransamVariables->xactCompletionCount = 1;
449 : : }
450 : :
5224 rhaas@postgresql.org 451 : 1150 : allProcs = ProcGlobal->allProcs;
452 : :
453 : : /* Create or attach to the KnownAssignedXids arrays too, if needed */
5799 tgl@sss.pgh.pa.us 454 [ + + ]: 1150 : if (EnableHotStandby)
455 : : {
5800 456 : 1144 : KnownAssignedXids = (TransactionId *)
457 : 1144 : ShmemInitStruct("KnownAssignedXids",
458 : : mul_size(sizeof(TransactionId),
459 : 1144 : TOTAL_MAX_CACHED_SUBXIDS),
460 : : &found);
461 : 1144 : KnownAssignedXidsValid = (bool *)
462 : 1144 : ShmemInitStruct("KnownAssignedXidsValid",
463 : 1144 : mul_size(sizeof(bool), TOTAL_MAX_CACHED_SUBXIDS),
464 : : &found);
465 : : }
7605 466 : 1150 : }
467 : :
468 : : /*
469 : : * Add the specified PGPROC to the shared array.
470 : : */
471 : : void
7576 472 : 17318 : ProcArrayAdd(PGPROC *proc)
473 : : {
752 heikki.linnakangas@i 474 : 17318 : int pgprocno = GetNumberFromPGProc(proc);
7605 tgl@sss.pgh.pa.us 475 : 17318 : ProcArrayStruct *arrayP = procArray;
476 : : int index;
477 : : int movecount;
478 : :
479 : : /* See ProcGlobal comment explaining why both locks are held */
480 : 17318 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
2039 andres@anarazel.de 481 : 17318 : LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
482 : :
7605 tgl@sss.pgh.pa.us 483 [ - + ]: 17318 : if (arrayP->numProcs >= arrayP->maxProcs)
484 : : {
485 : : /*
486 : : * Oops, no room. (This really shouldn't happen, since there is a
487 : : * fixed supply of PGPROC structs too, and so we should have failed
488 : : * earlier.)
489 : : */
7605 tgl@sss.pgh.pa.us 490 [ # # ]:UBC 0 : ereport(FATAL,
491 : : (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
492 : : errmsg("sorry, too many clients already")));
493 : : }
494 : :
495 : : /*
496 : : * Keep the procs array sorted by (PGPROC *) so that we can utilize
497 : : * locality of references much better. This is useful while traversing the
498 : : * ProcArray because there is an increased likelihood of finding the next
499 : : * PGPROC structure in the cache.
500 : : *
501 : : * Since the occurrence of adding/removing a proc is much lower than the
502 : : * access to the ProcArray itself, the overhead should be marginal
503 : : */
5224 rhaas@postgresql.org 504 [ + + ]:CBC 40226 : for (index = 0; index < arrayP->numProcs; index++)
505 : : {
752 heikki.linnakangas@i 506 : 35587 : int this_procno = arrayP->pgprocnos[index];
507 : :
508 [ + - - + ]: 35587 : Assert(this_procno >= 0 && this_procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
509 [ - + ]: 35587 : Assert(allProcs[this_procno].pgxactoff == index);
510 : :
511 : : /* If we have found our right position in the array, break */
512 [ + + ]: 35587 : if (this_procno > pgprocno)
5224 rhaas@postgresql.org 513 : 12679 : break;
514 : : }
515 : :
1738 andres@anarazel.de 516 : 17318 : movecount = arrayP->numProcs - index;
517 : 17318 : memmove(&arrayP->pgprocnos[index + 1],
518 : 17318 : &arrayP->pgprocnos[index],
519 : : movecount * sizeof(*arrayP->pgprocnos));
520 : 17318 : memmove(&ProcGlobal->xids[index + 1],
521 : 17318 : &ProcGlobal->xids[index],
522 : : movecount * sizeof(*ProcGlobal->xids));
523 : 17318 : memmove(&ProcGlobal->subxidStates[index + 1],
524 : 17318 : &ProcGlobal->subxidStates[index],
525 : : movecount * sizeof(*ProcGlobal->subxidStates));
526 : 17318 : memmove(&ProcGlobal->statusFlags[index + 1],
527 : 17318 : &ProcGlobal->statusFlags[index],
528 : : movecount * sizeof(*ProcGlobal->statusFlags));
529 : :
752 heikki.linnakangas@i 530 : 17318 : arrayP->pgprocnos[index] = GetNumberFromPGProc(proc);
1738 andres@anarazel.de 531 : 17318 : proc->pgxactoff = index;
2039 532 : 17318 : ProcGlobal->xids[index] = proc->xid;
533 : 17318 : ProcGlobal->subxidStates[index] = proc->subxidStatus;
1945 alvherre@alvh.no-ip. 534 : 17318 : ProcGlobal->statusFlags[index] = proc->statusFlags;
535 : :
7605 tgl@sss.pgh.pa.us 536 : 17318 : arrayP->numProcs++;
537 : :
538 : : /* adjust pgxactoff for all following PGPROCs */
1738 andres@anarazel.de 539 : 17318 : index++;
2039 540 [ + + ]: 48204 : for (; index < arrayP->numProcs; index++)
541 : : {
1738 542 : 30886 : int procno = arrayP->pgprocnos[index];
543 : :
544 [ + - - + ]: 30886 : Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
545 [ - + ]: 30886 : Assert(allProcs[procno].pgxactoff == index - 1);
546 : :
547 : 30886 : allProcs[procno].pgxactoff = index;
548 : : }
549 : :
550 : : /*
551 : : * Release in reversed acquisition order, to reduce frequency of having to
552 : : * wait for XidGenLock while holding ProcArrayLock.
553 : : */
2039 554 : 17318 : LWLockRelease(XidGenLock);
7605 tgl@sss.pgh.pa.us 555 : 17318 : LWLockRelease(ProcArrayLock);
556 : 17318 : }
557 : :
558 : : /*
559 : : * Remove the specified PGPROC from the shared array.
560 : : *
561 : : * When latestXid is a valid XID, we are removing a live 2PC gxact from the
562 : : * array, and thus causing it to appear as "not running" anymore. In this
563 : : * case we must advance latestCompletedXid. (This is essentially the same
564 : : * as ProcArrayEndTransaction followed by removal of the PGPROC, but we take
565 : : * the ProcArrayLock only once, and don't damage the content of the PGPROC;
566 : : * twophase.c depends on the latter.)
567 : : */
568 : : void
6763 569 : 17292 : ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
570 : : {
7605 571 : 17292 : ProcArrayStruct *arrayP = procArray;
572 : : int myoff;
573 : : int movecount;
574 : :
575 : : #ifdef XIDCACHE_DEBUG
576 : : /* dump stats at backend shutdown, but not prepared-xact end */
577 : : if (proc->pid != 0)
578 : : DisplayXidCache();
579 : : #endif
580 : :
581 : : /* See ProcGlobal comment explaining why both locks are held */
582 : 17292 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
2039 andres@anarazel.de 583 : 17292 : LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
584 : :
1738 585 : 17292 : myoff = proc->pgxactoff;
586 : :
587 [ + - - + ]: 17292 : Assert(myoff >= 0 && myoff < arrayP->numProcs);
588 [ - + ]: 17292 : Assert(ProcGlobal->allProcs[arrayP->pgprocnos[myoff]].pgxactoff == myoff);
589 : :
6763 tgl@sss.pgh.pa.us 590 [ + + ]: 17292 : if (TransactionIdIsValid(latestXid))
591 : : {
1738 andres@anarazel.de 592 [ - + ]: 322 : Assert(TransactionIdIsValid(ProcGlobal->xids[myoff]));
593 : :
594 : : /* Advance global latestCompletedXid while holding the lock */
2042 595 : 322 : MaintainLatestCompletedXid(latestXid);
596 : :
597 : : /* Same with xactCompletionCount */
828 heikki.linnakangas@i 598 : 322 : TransamVariables->xactCompletionCount++;
599 : :
1738 andres@anarazel.de 600 : 322 : ProcGlobal->xids[myoff] = InvalidTransactionId;
601 : 322 : ProcGlobal->subxidStates[myoff].overflowed = false;
602 : 322 : ProcGlobal->subxidStates[myoff].count = 0;
603 : : }
604 : : else
605 : : {
606 : : /* Shouldn't be trying to remove a live transaction here */
607 [ - + ]: 16970 : Assert(!TransactionIdIsValid(ProcGlobal->xids[myoff]));
608 : : }
609 : :
610 [ - + ]: 17292 : Assert(!TransactionIdIsValid(ProcGlobal->xids[myoff]));
611 [ - + ]: 17292 : Assert(ProcGlobal->subxidStates[myoff].count == 0);
612 [ - + ]: 17292 : Assert(ProcGlobal->subxidStates[myoff].overflowed == false);
613 : :
614 : 17292 : ProcGlobal->statusFlags[myoff] = 0;
615 : :
616 : : /* Keep the PGPROC array sorted. See notes above */
617 : 17292 : movecount = arrayP->numProcs - myoff - 1;
618 : 17292 : memmove(&arrayP->pgprocnos[myoff],
619 : 17292 : &arrayP->pgprocnos[myoff + 1],
620 : : movecount * sizeof(*arrayP->pgprocnos));
621 : 17292 : memmove(&ProcGlobal->xids[myoff],
622 : 17292 : &ProcGlobal->xids[myoff + 1],
623 : : movecount * sizeof(*ProcGlobal->xids));
624 : 17292 : memmove(&ProcGlobal->subxidStates[myoff],
625 : 17292 : &ProcGlobal->subxidStates[myoff + 1],
626 : : movecount * sizeof(*ProcGlobal->subxidStates));
627 : 17292 : memmove(&ProcGlobal->statusFlags[myoff],
628 : 17292 : &ProcGlobal->statusFlags[myoff + 1],
629 : : movecount * sizeof(*ProcGlobal->statusFlags));
630 : :
631 : 17292 : arrayP->pgprocnos[arrayP->numProcs - 1] = -1; /* for debugging */
632 : 17292 : arrayP->numProcs--;
633 : :
634 : : /*
635 : : * Adjust pgxactoff of following procs for removed PGPROC (note that
636 : : * numProcs already has been decremented).
637 : : */
638 [ + + ]: 51194 : for (int index = myoff; index < arrayP->numProcs; index++)
639 : : {
640 : 33902 : int procno = arrayP->pgprocnos[index];
641 : :
642 [ + - - + ]: 33902 : Assert(procno >= 0 && procno < (arrayP->maxProcs + NUM_AUXILIARY_PROCS));
643 [ - + ]: 33902 : Assert(allProcs[procno].pgxactoff - 1 == index);
644 : :
645 : 33902 : allProcs[procno].pgxactoff = index;
646 : : }
647 : :
648 : : /*
649 : : * Release in reversed acquisition order, to reduce frequency of having to
650 : : * wait for XidGenLock while holding ProcArrayLock.
651 : : */
2039 652 : 17292 : LWLockRelease(XidGenLock);
7605 tgl@sss.pgh.pa.us 653 : 17292 : LWLockRelease(ProcArrayLock);
654 : 17292 : }
655 : :
656 : :
657 : : /*
658 : : * ProcArrayEndTransaction -- mark a transaction as no longer running
659 : : *
660 : : * This is used interchangeably for commit and abort cases. The transaction
661 : : * commit/abort must already be reported to WAL and pg_xact.
662 : : *
663 : : * proc is currently always MyProc, but we pass it explicitly for flexibility.
664 : : * latestXid is the latest Xid among the transaction's main XID and
665 : : * subtransactions, or InvalidTransactionId if it has no XID. (We must ask
666 : : * the caller to pass latestXid, instead of computing it from the PGPROC's
667 : : * contents, because the subxid information in the PGPROC might be
668 : : * incomplete.)
669 : : */
670 : : void
6763 671 : 337497 : ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
672 : : {
673 [ + + ]: 337497 : if (TransactionIdIsValid(latestXid))
674 : : {
675 : : /*
676 : : * We must lock ProcArrayLock while clearing our advertised XID, so
677 : : * that we do not exit the set of "running" transactions while someone
678 : : * else is taking a snapshot. See discussion in
679 : : * src/backend/access/transam/README.
680 : : */
2039 andres@anarazel.de 681 [ - + ]: 132620 : Assert(TransactionIdIsValid(proc->xid));
682 : :
683 : : /*
684 : : * If we can immediately acquire ProcArrayLock, we clear our own XID
685 : : * and release the lock. If not, use group XID clearing to improve
686 : : * efficiency.
687 : : */
3874 rhaas@postgresql.org 688 [ + + ]: 132620 : if (LWLockConditionalAcquire(ProcArrayLock, LW_EXCLUSIVE))
689 : : {
2039 andres@anarazel.de 690 : 132475 : ProcArrayEndTransactionInternal(proc, latestXid);
3874 rhaas@postgresql.org 691 : 132475 : LWLockRelease(ProcArrayLock);
692 : : }
693 : : else
694 : 145 : ProcArrayGroupClearXid(proc, latestXid);
695 : : }
696 : : else
697 : : {
698 : : /*
699 : : * If we have no XID, we don't need to lock, since we won't affect
700 : : * anyone else's calculation of a snapshot. We might change their
701 : : * estimate of global xmin, but that's OK.
702 : : */
2039 andres@anarazel.de 703 [ - + ]: 204877 : Assert(!TransactionIdIsValid(proc->xid));
704 [ - + ]: 204877 : Assert(proc->subxidStatus.count == 0);
705 [ - + ]: 204877 : Assert(!proc->subxidStatus.overflowed);
706 : :
742 heikki.linnakangas@i 707 : 204877 : proc->vxid.lxid = InvalidLocalTransactionId;
2040 andres@anarazel.de 708 : 204877 : proc->xmin = InvalidTransactionId;
709 : :
710 : : /* be sure this is cleared in abort */
1437 rhaas@postgresql.org 711 : 204877 : proc->delayChkptFlags = 0;
712 : :
713 : : /* must be cleared with xid/xmin: */
714 : : /* avoid unnecessarily dirtying shared cachelines */
1945 alvherre@alvh.no-ip. 715 [ + + ]: 204877 : if (proc->statusFlags & PROC_VACUUM_STATE_MASK)
716 : : {
2069 andres@anarazel.de 717 [ - + ]: 14177 : Assert(!LWLockHeldByMe(ProcArrayLock));
1935 alvherre@alvh.no-ip. 718 : 14177 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
1945 719 [ - + ]: 14177 : Assert(proc->statusFlags == ProcGlobal->statusFlags[proc->pgxactoff]);
720 : 14177 : proc->statusFlags &= ~PROC_VACUUM_STATE_MASK;
721 : 14177 : ProcGlobal->statusFlags[proc->pgxactoff] = proc->statusFlags;
2069 andres@anarazel.de 722 : 14177 : LWLockRelease(ProcArrayLock);
723 : : }
724 : : }
6763 tgl@sss.pgh.pa.us 725 : 337497 : }
726 : :
727 : : /*
728 : : * Mark a write transaction as no longer running.
729 : : *
730 : : * We don't do any locking here; caller must handle that.
731 : : */
732 : : static inline void
2039 andres@anarazel.de 733 : 132620 : ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid)
734 : : {
1641 fujii@postgresql.org 735 : 132620 : int pgxactoff = proc->pgxactoff;
736 : :
737 : : /*
738 : : * Note: we need exclusive lock here because we're going to change other
739 : : * processes' PGPROC entries.
740 : : */
1943 alvherre@alvh.no-ip. 741 [ - + ]: 132620 : Assert(LWLockHeldByMeInMode(ProcArrayLock, LW_EXCLUSIVE));
2039 andres@anarazel.de 742 [ - + ]: 132620 : Assert(TransactionIdIsValid(ProcGlobal->xids[pgxactoff]));
743 [ - + ]: 132620 : Assert(ProcGlobal->xids[pgxactoff] == proc->xid);
744 : :
745 : 132620 : ProcGlobal->xids[pgxactoff] = InvalidTransactionId;
746 : 132620 : proc->xid = InvalidTransactionId;
742 heikki.linnakangas@i 747 : 132620 : proc->vxid.lxid = InvalidLocalTransactionId;
2040 andres@anarazel.de 748 : 132620 : proc->xmin = InvalidTransactionId;
749 : :
750 : : /* be sure this is cleared in abort */
1437 rhaas@postgresql.org 751 : 132620 : proc->delayChkptFlags = 0;
752 : :
753 : : /* must be cleared with xid/xmin: */
754 : : /* avoid unnecessarily dirtying shared cachelines */
1945 alvherre@alvh.no-ip. 755 [ + + ]: 132620 : if (proc->statusFlags & PROC_VACUUM_STATE_MASK)
756 : : {
757 : 774 : proc->statusFlags &= ~PROC_VACUUM_STATE_MASK;
758 : 774 : ProcGlobal->statusFlags[proc->pgxactoff] = proc->statusFlags;
759 : : }
760 : :
761 : : /* Clear the subtransaction-XID cache too while holding the lock */
2039 andres@anarazel.de 762 [ + - - + ]: 132620 : Assert(ProcGlobal->subxidStates[pgxactoff].count == proc->subxidStatus.count &&
763 : : ProcGlobal->subxidStates[pgxactoff].overflowed == proc->subxidStatus.overflowed);
764 [ + + - + ]: 132620 : if (proc->subxidStatus.count > 0 || proc->subxidStatus.overflowed)
765 : : {
766 : 462 : ProcGlobal->subxidStates[pgxactoff].count = 0;
767 : 462 : ProcGlobal->subxidStates[pgxactoff].overflowed = false;
768 : 462 : proc->subxidStatus.count = 0;
769 : 462 : proc->subxidStatus.overflowed = false;
770 : : }
771 : :
772 : : /* Also advance global latestCompletedXid while holding the lock */
2042 773 : 132620 : MaintainLatestCompletedXid(latestXid);
774 : :
775 : : /* Same with xactCompletionCount */
828 heikki.linnakangas@i 776 : 132620 : TransamVariables->xactCompletionCount++;
3874 rhaas@postgresql.org 777 : 132620 : }
778 : :
779 : : /*
780 : : * ProcArrayGroupClearXid -- group XID clearing
781 : : *
782 : : * When we cannot immediately acquire ProcArrayLock in exclusive mode at
783 : : * commit time, add ourselves to a list of processes that need their XIDs
784 : : * cleared. The first process to add itself to the list will acquire
785 : : * ProcArrayLock in exclusive mode and perform ProcArrayEndTransactionInternal
786 : : * on behalf of all group members. This avoids a great deal of contention
787 : : * around ProcArrayLock when many processes are trying to commit at once,
788 : : * since the lock need not be repeatedly handed off from one committing
789 : : * process to the next.
790 : : */
791 : : static void
792 : 145 : ProcArrayGroupClearXid(PGPROC *proc, TransactionId latestXid)
793 : : {
752 heikki.linnakangas@i 794 : 145 : int pgprocno = GetNumberFromPGProc(proc);
2683 andres@anarazel.de 795 : 145 : PROC_HDR *procglobal = ProcGlobal;
796 : : uint32 nextidx;
797 : : uint32 wakeidx;
798 : :
799 : : /* We should definitely have an XID to clear. */
2039 800 [ - + ]: 145 : Assert(TransactionIdIsValid(proc->xid));
801 : :
802 : : /* Add ourselves to the list of processes needing a group XID clear. */
3685 rhaas@postgresql.org 803 : 145 : proc->procArrayGroupMember = true;
804 : 145 : proc->procArrayGroupMemberXid = latestXid;
2340 noah@leadboat.com 805 : 145 : nextidx = pg_atomic_read_u32(&procglobal->procArrayGroupFirst);
806 : : while (true)
807 : : {
3685 rhaas@postgresql.org 808 : 145 : pg_atomic_write_u32(&proc->procArrayGroupNext, nextidx);
809 : :
810 [ + - ]: 145 : if (pg_atomic_compare_exchange_u32(&procglobal->procArrayGroupFirst,
811 : : &nextidx,
812 : : (uint32) pgprocno))
3874 813 : 145 : break;
814 : : }
815 : :
816 : : /*
817 : : * If the list was not empty, the leader will clear our XID. It is
818 : : * impossible to have followers without a leader because the first process
819 : : * that has added itself to the list will always have nextidx as
820 : : * INVALID_PROC_NUMBER.
821 : : */
742 heikki.linnakangas@i 822 [ + + ]: 145 : if (nextidx != INVALID_PROC_NUMBER)
823 : : {
3356 rhaas@postgresql.org 824 : 41 : int extraWaits = 0;
825 : :
826 : : /* Sleep until the leader clears our XID. */
3264 827 : 41 : pgstat_report_wait_start(WAIT_EVENT_PROCARRAY_GROUP_UPDATE);
828 : : for (;;)
829 : : {
830 : : /* acts as a read barrier */
3380 tgl@sss.pgh.pa.us 831 : 41 : PGSemaphoreLock(proc->sem);
3685 rhaas@postgresql.org 832 [ + - ]: 41 : if (!proc->procArrayGroupMember)
3846 833 : 41 : break;
3846 rhaas@postgresql.org 834 :UBC 0 : extraWaits++;
835 : : }
3264 rhaas@postgresql.org 836 :CBC 41 : pgstat_report_wait_end();
837 : :
742 heikki.linnakangas@i 838 [ - + ]: 41 : Assert(pg_atomic_read_u32(&proc->procArrayGroupNext) == INVALID_PROC_NUMBER);
839 : :
840 : : /* Fix semaphore count for any absorbed wakeups */
3874 rhaas@postgresql.org 841 [ - + ]: 41 : while (extraWaits-- > 0)
3380 tgl@sss.pgh.pa.us 842 :UBC 0 : PGSemaphoreUnlock(proc->sem);
3874 rhaas@postgresql.org 843 :CBC 41 : return;
844 : : }
845 : :
846 : : /* We are the leader. Acquire the lock on behalf of everyone. */
847 : 104 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
848 : :
849 : : /*
850 : : * Now that we've got the lock, clear the list of processes waiting for
851 : : * group XID clearing, saving a pointer to the head of the list. Trying
852 : : * to pop elements one at a time could lead to an ABA problem.
853 : : */
2731 akorotkov@postgresql 854 : 104 : nextidx = pg_atomic_exchange_u32(&procglobal->procArrayGroupFirst,
855 : : INVALID_PROC_NUMBER);
856 : :
857 : : /* Remember head of list so we can perform wakeups after dropping lock. */
3874 rhaas@postgresql.org 858 : 104 : wakeidx = nextidx;
859 : :
860 : : /* Walk the list and clear all XIDs. */
742 heikki.linnakangas@i 861 [ + + ]: 249 : while (nextidx != INVALID_PROC_NUMBER)
862 : : {
1641 fujii@postgresql.org 863 : 145 : PGPROC *nextproc = &allProcs[nextidx];
864 : :
865 : 145 : ProcArrayEndTransactionInternal(nextproc, nextproc->procArrayGroupMemberXid);
866 : :
867 : : /* Move to next proc in list. */
868 : 145 : nextidx = pg_atomic_read_u32(&nextproc->procArrayGroupNext);
869 : : }
870 : :
871 : : /* We're done with the lock now. */
3874 rhaas@postgresql.org 872 : 104 : LWLockRelease(ProcArrayLock);
873 : :
874 : : /*
875 : : * Now that we've released the lock, go back and wake everybody up. We
876 : : * don't do this under the lock so as to keep lock hold times to a
877 : : * minimum. The system calls we need to perform to wake other processes
878 : : * up are probably much slower than the simple memory writes we did while
879 : : * holding the lock.
880 : : */
742 heikki.linnakangas@i 881 [ + + ]: 249 : while (wakeidx != INVALID_PROC_NUMBER)
882 : : {
1641 fujii@postgresql.org 883 : 145 : PGPROC *nextproc = &allProcs[wakeidx];
884 : :
885 : 145 : wakeidx = pg_atomic_read_u32(&nextproc->procArrayGroupNext);
742 heikki.linnakangas@i 886 : 145 : pg_atomic_write_u32(&nextproc->procArrayGroupNext, INVALID_PROC_NUMBER);
887 : :
888 : : /* ensure all previous writes are visible before follower continues. */
3846 rhaas@postgresql.org 889 : 145 : pg_write_barrier();
890 : :
1641 fujii@postgresql.org 891 : 145 : nextproc->procArrayGroupMember = false;
892 : :
893 [ + + ]: 145 : if (nextproc != MyProc)
894 : 41 : PGSemaphoreUnlock(nextproc->sem);
895 : : }
896 : : }
897 : :
898 : : /*
899 : : * ProcArrayClearTransaction -- clear the transaction fields
900 : : *
901 : : * This is used after successfully preparing a 2-phase transaction. We are
902 : : * not actually reporting the transaction's XID as no longer running --- it
903 : : * will still appear as running because the 2PC's gxact is in the ProcArray
904 : : * too. We just have to clear out our own PGPROC.
905 : : */
906 : : void
6763 tgl@sss.pgh.pa.us 907 : 315 : ProcArrayClearTransaction(PGPROC *proc)
908 : : {
909 : : int pgxactoff;
910 : :
911 : : /*
912 : : * Currently we need to lock ProcArrayLock exclusively here, as we
913 : : * increment xactCompletionCount below. We also need it at least in shared
914 : : * mode for pgproc->pgxactoff to stay the same below.
915 : : *
916 : : * We could however, as this action does not actually change anyone's view
917 : : * of the set of running XIDs (our entry is duplicate with the gxact that
918 : : * has already been inserted into the ProcArray), lower the lock level to
919 : : * shared if we were to make xactCompletionCount an atomic variable. But
920 : : * that doesn't seem worth it currently, as a 2PC commit is heavyweight
921 : : * enough for this not to be the bottleneck. If it ever becomes a
922 : : * bottleneck it may also be worth considering to combine this with the
923 : : * subsequent ProcArrayRemove()
924 : : */
2034 andres@anarazel.de 925 : 315 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
926 : :
2039 927 : 315 : pgxactoff = proc->pgxactoff;
928 : :
929 : 315 : ProcGlobal->xids[pgxactoff] = InvalidTransactionId;
930 : 315 : proc->xid = InvalidTransactionId;
931 : :
742 heikki.linnakangas@i 932 : 315 : proc->vxid.lxid = InvalidLocalTransactionId;
2040 andres@anarazel.de 933 : 315 : proc->xmin = InvalidTransactionId;
934 : :
1945 alvherre@alvh.no-ip. 935 [ - + ]: 315 : Assert(!(proc->statusFlags & PROC_VACUUM_STATE_MASK));
1437 rhaas@postgresql.org 936 [ - + ]: 315 : Assert(!proc->delayChkptFlags);
937 : :
938 : : /*
939 : : * Need to increment completion count even though transaction hasn't
940 : : * really committed yet. The reason for that is that GetSnapshotData()
941 : : * omits the xid of the current transaction, thus without the increment we
942 : : * otherwise could end up reusing the snapshot later. Which would be bad,
943 : : * because it might not count the prepared transaction as running.
944 : : */
828 heikki.linnakangas@i 945 : 315 : TransamVariables->xactCompletionCount++;
946 : :
947 : : /* Clear the subtransaction-XID cache too */
2039 andres@anarazel.de 948 [ + - - + ]: 315 : Assert(ProcGlobal->subxidStates[pgxactoff].count == proc->subxidStatus.count &&
949 : : ProcGlobal->subxidStates[pgxactoff].overflowed == proc->subxidStatus.overflowed);
950 [ + + - + ]: 315 : if (proc->subxidStatus.count > 0 || proc->subxidStatus.overflowed)
951 : : {
952 : 101 : ProcGlobal->subxidStates[pgxactoff].count = 0;
953 : 101 : ProcGlobal->subxidStates[pgxactoff].overflowed = false;
954 : 101 : proc->subxidStatus.count = 0;
955 : 101 : proc->subxidStatus.overflowed = false;
956 : : }
957 : :
958 : 315 : LWLockRelease(ProcArrayLock);
6763 tgl@sss.pgh.pa.us 959 : 315 : }
960 : :
961 : : /*
962 : : * Update TransamVariables->latestCompletedXid to point to latestXid if
963 : : * currently older.
964 : : */
965 : : static void
2042 andres@anarazel.de 966 : 133610 : MaintainLatestCompletedXid(TransactionId latestXid)
967 : : {
828 heikki.linnakangas@i 968 : 133610 : FullTransactionId cur_latest = TransamVariables->latestCompletedXid;
969 : :
2042 andres@anarazel.de 970 [ - + ]: 133610 : Assert(FullTransactionIdIsValid(cur_latest));
971 [ - + ]: 133610 : Assert(!RecoveryInProgress());
972 [ - + ]: 133610 : Assert(LWLockHeldByMe(ProcArrayLock));
973 : :
974 [ + + ]: 133610 : if (TransactionIdPrecedes(XidFromFullTransactionId(cur_latest), latestXid))
975 : : {
828 heikki.linnakangas@i 976 : 117615 : TransamVariables->latestCompletedXid =
2042 andres@anarazel.de 977 : 117615 : FullXidRelativeTo(cur_latest, latestXid);
978 : : }
979 : :
980 [ + + - + ]: 133610 : Assert(IsBootstrapProcessingMode() ||
981 : : FullTransactionIdIsNormal(TransamVariables->latestCompletedXid));
982 : 133610 : }
983 : :
984 : : /*
985 : : * Same as MaintainLatestCompletedXid, except for use during WAL replay.
986 : : */
987 : : static void
988 : 23523 : MaintainLatestCompletedXidRecovery(TransactionId latestXid)
989 : : {
828 heikki.linnakangas@i 990 : 23523 : FullTransactionId cur_latest = TransamVariables->latestCompletedXid;
991 : : FullTransactionId rel;
992 : :
2042 andres@anarazel.de 993 [ - + - - ]: 23523 : Assert(AmStartupProcess() || !IsUnderPostmaster);
994 [ - + ]: 23523 : Assert(LWLockHeldByMe(ProcArrayLock));
995 : :
996 : : /*
997 : : * Need a FullTransactionId to compare latestXid with. Can't rely on
998 : : * latestCompletedXid to be initialized in recovery. But in recovery it's
999 : : * safe to access nextXid without a lock for the startup process.
1000 : : */
828 heikki.linnakangas@i 1001 : 23523 : rel = TransamVariables->nextXid;
1002 [ - + ]: 23523 : Assert(FullTransactionIdIsValid(TransamVariables->nextXid));
1003 : :
2042 andres@anarazel.de 1004 [ + + + + ]: 46932 : if (!FullTransactionIdIsValid(cur_latest) ||
1005 : 23409 : TransactionIdPrecedes(XidFromFullTransactionId(cur_latest), latestXid))
1006 : : {
828 heikki.linnakangas@i 1007 : 17052 : TransamVariables->latestCompletedXid =
2042 andres@anarazel.de 1008 : 17052 : FullXidRelativeTo(rel, latestXid);
1009 : : }
1010 : :
828 heikki.linnakangas@i 1011 [ - + ]: 23523 : Assert(FullTransactionIdIsNormal(TransamVariables->latestCompletedXid));
2042 andres@anarazel.de 1012 : 23523 : }
1013 : :
1014 : : /*
1015 : : * ProcArrayInitRecovery -- initialize recovery xid mgmt environment
1016 : : *
1017 : : * Remember up to where the startup process initialized the CLOG and subtrans
1018 : : * so we can ensure it's initialized gaplessly up to the point where necessary
1019 : : * while in recovery.
1020 : : */
1021 : : void
4648 simon@2ndQuadrant.co 1022 : 114 : ProcArrayInitRecovery(TransactionId initializedUptoXID)
1023 : : {
1024 [ - + ]: 114 : Assert(standbyState == STANDBY_INITIALIZED);
1025 [ - + ]: 114 : Assert(TransactionIdIsNormal(initializedUptoXID));
1026 : :
1027 : : /*
1028 : : * we set latestObservedXid to the xid SUBTRANS has been initialized up
1029 : : * to, so we can extend it from that point onwards in
1030 : : * RecordKnownAssignedTransactionIds, and when we get consistent in
1031 : : * ProcArrayApplyRecoveryInfo().
1032 : : */
1033 : 114 : latestObservedXid = initializedUptoXID;
1034 [ - + ]: 114 : TransactionIdRetreat(latestObservedXid);
1035 : 114 : }
1036 : :
1037 : : /*
1038 : : * ProcArrayApplyRecoveryInfo -- apply recovery info about xids
1039 : : *
1040 : : * Takes us through 3 states: Initialized, Pending and Ready.
1041 : : * Normal case is to go all the way to Ready straight away, though there
1042 : : * are atypical cases where we need to take it in steps.
1043 : : *
1044 : : * Use the data about running transactions on the primary to create the initial
1045 : : * state of KnownAssignedXids. We also use these records to regularly prune
1046 : : * KnownAssignedXids because we know it is possible that some transactions
1047 : : * with FATAL errors fail to write abort records, which could cause eventual
1048 : : * overflow.
1049 : : *
1050 : : * See comments for LogStandbySnapshot().
1051 : : */
1052 : : void
5930 1053 : 824 : ProcArrayApplyRecoveryInfo(RunningTransactions running)
1054 : : {
1055 : : TransactionId *xids;
1056 : : TransactionId advanceNextXid;
1057 : : int nxids;
1058 : : int i;
1059 : :
1060 [ - + ]: 824 : Assert(standbyState >= STANDBY_INITIALIZED);
5784 1061 [ - + ]: 824 : Assert(TransactionIdIsValid(running->nextXid));
1062 [ - + ]: 824 : Assert(TransactionIdIsValid(running->oldestRunningXid));
1063 [ - + ]: 824 : Assert(TransactionIdIsNormal(running->latestCompletedXid));
1064 : :
1065 : : /*
1066 : : * Remove stale transactions, if any.
1067 : : */
5930 1068 : 824 : ExpireOldKnownAssignedTransactionIds(running->oldestRunningXid);
1069 : :
1070 : : /*
1071 : : * Adjust TransamVariables->nextXid before StandbyReleaseOldLocks(),
1072 : : * because we will need it up to date for accessing two-phase transactions
1073 : : * in StandbyReleaseOldLocks().
1074 : : */
786 akorotkov@postgresql 1075 : 824 : advanceNextXid = running->nextXid;
1076 [ - + ]: 824 : TransactionIdRetreat(advanceNextXid);
1077 : 824 : AdvanceNextFullTransactionIdPastXid(advanceNextXid);
1078 [ - + ]: 824 : Assert(FullTransactionIdIsValid(TransamVariables->nextXid));
1079 : :
1080 : : /*
1081 : : * Remove stale locks, if any.
1082 : : */
2829 simon@2ndQuadrant.co 1083 : 824 : StandbyReleaseOldLocks(running->oldestRunningXid);
1084 : :
1085 : : /*
1086 : : * If our snapshot is already valid, nothing else to do...
1087 : : */
5930 1088 [ + + ]: 824 : if (standbyState == STANDBY_SNAPSHOT_READY)
1089 : 710 : return;
1090 : :
1091 : : /*
1092 : : * If our initial RunningTransactionsData had an overflowed snapshot then
1093 : : * we knew we were missing some subxids from our snapshot. If we continue
1094 : : * to see overflowed snapshots then we might never be able to start up, so
1095 : : * we make another test to see if our snapshot is now valid. We know that
1096 : : * the missing subxids are equal to or earlier than nextXid. After we
1097 : : * initialise we continue to apply changes during recovery, so once the
1098 : : * oldestRunningXid is later than the nextXid from the initial snapshot we
1099 : : * know that we no longer have missing information and can mark the
1100 : : * snapshot as valid.
1101 : : */
1102 [ - + ]: 114 : if (standbyState == STANDBY_SNAPSHOT_PENDING)
1103 : : {
1104 : : /*
1105 : : * If the snapshot isn't overflowed or if its empty we can reset our
1106 : : * pending state and use this snapshot instead.
1107 : : */
626 heikki.linnakangas@i 1108 [ # # # # ]:UBC 0 : if (running->subxid_status != SUBXIDS_MISSING || running->xcnt == 0)
1109 : : {
1110 : : /*
1111 : : * If we have already collected known assigned xids, we need to
1112 : : * throw them away before we apply the recovery snapshot.
1113 : : */
5028 simon@2ndQuadrant.co 1114 : 0 : KnownAssignedXidsReset();
5247 1115 : 0 : standbyState = STANDBY_INITIALIZED;
1116 : : }
1117 : : else
1118 : : {
1119 [ # # ]: 0 : if (TransactionIdPrecedes(standbySnapshotPendingXmin,
1120 : : running->oldestRunningXid))
1121 : : {
1122 : 0 : standbyState = STANDBY_SNAPSHOT_READY;
825 michael@paquier.xyz 1123 [ # # ]: 0 : elog(DEBUG1,
1124 : : "recovery snapshots are now enabled");
1125 : : }
1126 : : else
1127 [ # # ]: 0 : elog(DEBUG1,
1128 : : "recovery snapshot waiting for non-overflowed snapshot or "
1129 : : "until oldest active xid on standby is at least %u (now %u)",
1130 : : standbySnapshotPendingXmin,
1131 : : running->oldestRunningXid);
5247 simon@2ndQuadrant.co 1132 : 0 : return;
1133 : : }
1134 : : }
1135 : :
5785 simon@2ndQuadrant.co 1136 [ - + ]:CBC 114 : Assert(standbyState == STANDBY_INITIALIZED);
1137 : :
1138 : : /*
1139 : : * NB: this can be reached at least twice, so make sure new code can deal
1140 : : * with that.
1141 : : */
1142 : :
1143 : : /*
1144 : : * Nobody else is running yet, but take locks anyhow
1145 : : */
1146 : 114 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
1147 : :
1148 : : /*
1149 : : * KnownAssignedXids is sorted so we cannot just add the xids, we have to
1150 : : * sort them first.
1151 : : *
1152 : : * Some of the new xids are top-level xids and some are subtransactions.
1153 : : * We don't call SubTransSetParent because it doesn't matter yet. If we
1154 : : * aren't overflowed then all xids will fit in snapshot and so we don't
1155 : : * need subtrans. If we later overflow, an xid assignment record will add
1156 : : * xids to subtrans. If RunningTransactionsData is overflowed then we
1157 : : * don't have enough information to correctly update subtrans anyway.
1158 : : */
1159 : :
1160 : : /*
1161 : : * Allocate a temporary array to avoid modifying the array passed as
1162 : : * argument.
1163 : : */
95 michael@paquier.xyz 1164 :GNC 114 : xids = palloc_array(TransactionId, running->xcnt + running->subxcnt);
1165 : :
1166 : : /*
1167 : : * Add to the temp array any xids which have not already completed.
1168 : : */
5577 heikki.linnakangas@i 1169 :CBC 114 : nxids = 0;
4851 simon@2ndQuadrant.co 1170 [ + + ]: 119 : for (i = 0; i < running->xcnt + running->subxcnt; i++)
1171 : : {
5785 1172 : 5 : TransactionId xid = running->xids[i];
1173 : :
1174 : : /*
1175 : : * The running-xacts snapshot can contain xids that were still visible
1176 : : * in the procarray when the snapshot was taken, but were already
1177 : : * WAL-logged as completed. They're not running anymore, so ignore
1178 : : * them.
1179 : : */
5930 1180 [ + - - + ]: 5 : if (TransactionIdDidCommit(xid) || TransactionIdDidAbort(xid))
5930 simon@2ndQuadrant.co 1181 :UBC 0 : continue;
1182 : :
5785 simon@2ndQuadrant.co 1183 :CBC 5 : xids[nxids++] = xid;
1184 : : }
1185 : :
1186 [ + + ]: 114 : if (nxids > 0)
1187 : : {
5028 1188 [ - + ]: 5 : if (procArray->numKnownAssignedXids != 0)
1189 : : {
5028 simon@2ndQuadrant.co 1190 :UBC 0 : LWLockRelease(ProcArrayLock);
1191 [ # # ]: 0 : elog(ERROR, "KnownAssignedXids is not empty");
1192 : : }
1193 : :
1194 : : /*
1195 : : * Sort the array so that we can add them safely into
1196 : : * KnownAssignedXids.
1197 : : *
1198 : : * We have to sort them logically, because in KnownAssignedXidsAdd we
1199 : : * call TransactionIdFollowsOrEquals and so on. But we know these XIDs
1200 : : * come from RUNNING_XACTS, which means there are only normal XIDs
1201 : : * from the same epoch, so this is safe.
1202 : : */
1508 tomas.vondra@postgre 1203 :CBC 5 : qsort(xids, nxids, sizeof(TransactionId), xidLogicalComparator);
1204 : :
1205 : : /*
1206 : : * Add the sorted snapshot into KnownAssignedXids. The running-xacts
1207 : : * snapshot may include duplicated xids because of prepared
1208 : : * transactions, so ignore them.
1209 : : */
5785 simon@2ndQuadrant.co 1210 [ + + ]: 10 : for (i = 0; i < nxids; i++)
1211 : : {
2709 michael@paquier.xyz 1212 [ - + - - ]: 5 : if (i > 0 && TransactionIdEquals(xids[i - 1], xids[i]))
1213 : : {
2709 michael@paquier.xyz 1214 [ # # ]:UBC 0 : elog(DEBUG1,
1215 : : "found duplicated transaction %u for KnownAssignedXids insertion",
1216 : : xids[i]);
1217 : 0 : continue;
1218 : : }
5577 heikki.linnakangas@i 1219 :CBC 5 : KnownAssignedXidsAdd(xids[i], xids[i], true);
1220 : : }
1221 : :
825 michael@paquier.xyz 1222 : 5 : KnownAssignedXidsDisplay(DEBUG3);
1223 : : }
1224 : :
5785 simon@2ndQuadrant.co 1225 : 114 : pfree(xids);
1226 : :
1227 : : /*
1228 : : * latestObservedXid is at least set to the point where SUBTRANS was
1229 : : * started up to (cf. ProcArrayInitRecovery()) or to the biggest xid
1230 : : * RecordKnownAssignedTransactionIds() was called for. Initialize
1231 : : * subtrans from thereon, up to nextXid - 1.
1232 : : *
1233 : : * We need to duplicate parts of RecordKnownAssignedTransactionId() here,
1234 : : * because we've just added xids to the known assigned xids machinery that
1235 : : * haven't gone through RecordKnownAssignedTransactionId().
1236 : : */
4648 1237 [ - + ]: 114 : Assert(TransactionIdIsNormal(latestObservedXid));
4496 heikki.linnakangas@i 1238 [ - + ]: 114 : TransactionIdAdvance(latestObservedXid);
4648 simon@2ndQuadrant.co 1239 [ - + ]: 228 : while (TransactionIdPrecedes(latestObservedXid, running->nextXid))
1240 : : {
4648 simon@2ndQuadrant.co 1241 :UBC 0 : ExtendSUBTRANS(latestObservedXid);
1242 [ # # ]: 0 : TransactionIdAdvance(latestObservedXid);
1243 : : }
4331 bruce@momjian.us 1244 [ - + ]:CBC 114 : TransactionIdRetreat(latestObservedXid); /* = running->nextXid - 1 */
1245 : :
1246 : : /* ----------
1247 : : * Now we've got the running xids we need to set the global values that
1248 : : * are used to track snapshots as they evolve further.
1249 : : *
1250 : : * - latestCompletedXid which will be the xmax for snapshots
1251 : : * - lastOverflowedXid which shows whether snapshots overflow
1252 : : * - nextXid
1253 : : *
1254 : : * If the snapshot overflowed, then we still initialise with what we know,
1255 : : * but the recovery snapshot isn't fully valid yet because we know there
1256 : : * are some subxids missing. We don't know the specific subxids that are
1257 : : * missing, so conservatively assume the last one is latestObservedXid.
1258 : : * ----------
1259 : : */
626 heikki.linnakangas@i 1260 [ - + ]: 114 : if (running->subxid_status == SUBXIDS_MISSING)
1261 : : {
5785 simon@2ndQuadrant.co 1262 :UBC 0 : standbyState = STANDBY_SNAPSHOT_PENDING;
1263 : :
1264 : 0 : standbySnapshotPendingXmin = latestObservedXid;
5577 heikki.linnakangas@i 1265 : 0 : procArray->lastOverflowedXid = latestObservedXid;
1266 : : }
1267 : : else
1268 : : {
5785 simon@2ndQuadrant.co 1269 :CBC 114 : standbyState = STANDBY_SNAPSHOT_READY;
1270 : :
1271 : 114 : standbySnapshotPendingXmin = InvalidTransactionId;
1272 : :
1273 : : /*
1274 : : * If the 'xids' array didn't include all subtransactions, we have to
1275 : : * mark any snapshots taken as overflowed.
1276 : : */
626 heikki.linnakangas@i 1277 [ + + ]: 114 : if (running->subxid_status == SUBXIDS_IN_SUBTRANS)
1278 : 26 : procArray->lastOverflowedXid = latestObservedXid;
1279 : : else
1280 : : {
1281 [ - + ]: 88 : Assert(running->subxid_status == SUBXIDS_IN_ARRAY);
1282 : 88 : procArray->lastOverflowedXid = InvalidTransactionId;
1283 : : }
1284 : : }
1285 : :
1286 : : /*
1287 : : * If a transaction wrote a commit record in the gap between taking and
1288 : : * logging the snapshot then latestCompletedXid may already be higher than
1289 : : * the value from the snapshot, so check before we use the incoming value.
1290 : : * It also might not yet be set at all.
1291 : : */
2042 andres@anarazel.de 1292 : 114 : MaintainLatestCompletedXidRecovery(running->latestCompletedXid);
1293 : :
1294 : : /*
1295 : : * NB: No need to increment TransamVariables->xactCompletionCount here,
1296 : : * nobody can see it yet.
1297 : : */
1298 : :
5151 tgl@sss.pgh.pa.us 1299 : 114 : LWLockRelease(ProcArrayLock);
1300 : :
825 michael@paquier.xyz 1301 : 114 : KnownAssignedXidsDisplay(DEBUG3);
5930 simon@2ndQuadrant.co 1302 [ + - ]: 114 : if (standbyState == STANDBY_SNAPSHOT_READY)
825 michael@paquier.xyz 1303 [ + + ]: 114 : elog(DEBUG1, "recovery snapshots are now enabled");
1304 : : else
825 michael@paquier.xyz 1305 [ # # ]:UBC 0 : elog(DEBUG1,
1306 : : "recovery snapshot waiting for non-overflowed snapshot or "
1307 : : "until oldest active xid on standby is at least %u (now %u)",
1308 : : standbySnapshotPendingXmin,
1309 : : running->oldestRunningXid);
1310 : : }
1311 : :
1312 : : /*
1313 : : * ProcArrayApplyXidAssignment
1314 : : * Process an XLOG_XACT_ASSIGNMENT WAL record
1315 : : */
1316 : : void
5930 simon@2ndQuadrant.co 1317 :CBC 21 : ProcArrayApplyXidAssignment(TransactionId topxid,
1318 : : int nsubxids, TransactionId *subxids)
1319 : : {
1320 : : TransactionId max_xid;
1321 : : int i;
1322 : :
5785 1323 [ - + ]: 21 : Assert(standbyState >= STANDBY_INITIALIZED);
1324 : :
5930 1325 : 21 : max_xid = TransactionIdLatest(topxid, nsubxids, subxids);
1326 : :
1327 : : /*
1328 : : * Mark all the subtransactions as observed.
1329 : : *
1330 : : * NOTE: This will fail if the subxid contains too many previously
1331 : : * unobserved xids to fit into known-assigned-xids. That shouldn't happen
1332 : : * as the code stands, because xid-assignment records should never contain
1333 : : * more than PGPROC_MAX_CACHED_SUBXIDS entries.
1334 : : */
1335 : 21 : RecordKnownAssignedTransactionIds(max_xid);
1336 : :
1337 : : /*
1338 : : * Notice that we update pg_subtrans with the top-level xid, rather than
1339 : : * the parent xid. This is a difference between normal processing and
1340 : : * recovery, yet is still correct in all cases. The reason is that
1341 : : * subtransaction commit is not marked in clog until commit processing, so
1342 : : * all aborted subtransactions have already been clearly marked in clog.
1343 : : * As a result we are able to refer directly to the top-level
1344 : : * transaction's state rather than skipping through all the intermediate
1345 : : * states in the subtransaction tree. This should be the first time we
1346 : : * have attempted to SubTransSetParent().
1347 : : */
1348 [ + + ]: 1365 : for (i = 0; i < nsubxids; i++)
3244 1349 : 1344 : SubTransSetParent(subxids[i], topxid);
1350 : :
1351 : : /* KnownAssignedXids isn't maintained yet, so we're done for now */
4496 heikki.linnakangas@i 1352 [ - + ]: 21 : if (standbyState == STANDBY_INITIALIZED)
4496 heikki.linnakangas@i 1353 :UBC 0 : return;
1354 : :
1355 : : /*
1356 : : * Uses same locking as transaction commit
1357 : : */
5930 simon@2ndQuadrant.co 1358 :CBC 21 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
1359 : :
1360 : : /*
1361 : : * Remove subxids from known-assigned-xacts.
1362 : : */
5800 tgl@sss.pgh.pa.us 1363 : 21 : KnownAssignedXidsRemoveTree(InvalidTransactionId, nsubxids, subxids);
1364 : :
1365 : : /*
1366 : : * Advance lastOverflowedXid to be at least the last of these subxids.
1367 : : */
5930 simon@2ndQuadrant.co 1368 [ + - ]: 21 : if (TransactionIdPrecedes(procArray->lastOverflowedXid, max_xid))
1369 : 21 : procArray->lastOverflowedXid = max_xid;
1370 : :
1371 : 21 : LWLockRelease(ProcArrayLock);
1372 : : }
1373 : :
1374 : : /*
1375 : : * TransactionIdIsInProgress -- is given transaction running in some backend
1376 : : *
1377 : : * Aside from some shortcuts such as checking RecentXmin and our own Xid,
1378 : : * there are four possibilities for finding a running transaction:
1379 : : *
1380 : : * 1. The given Xid is a main transaction Id. We will find this out cheaply
1381 : : * by looking at ProcGlobal->xids.
1382 : : *
1383 : : * 2. The given Xid is one of the cached subxact Xids in the PGPROC array.
1384 : : * We can find this out cheaply too.
1385 : : *
1386 : : * 3. In Hot Standby mode, we must search the KnownAssignedXids list to see
1387 : : * if the Xid is running on the primary.
1388 : : *
1389 : : * 4. Search the SubTrans tree to find the Xid's topmost parent, and then see
1390 : : * if that is running according to ProcGlobal->xids[] or KnownAssignedXids.
1391 : : * This is the slowest way, but sadly it has to be done always if the others
1392 : : * failed, unless we see that the cached subxact sets are complete (none have
1393 : : * overflowed).
1394 : : *
1395 : : * ProcArrayLock has to be held while we do 1, 2, 3. If we save the top Xids
1396 : : * while doing 1 and 3, we can release the ProcArrayLock while we do 4.
1397 : : * This buys back some concurrency (and we can't retrieve the main Xids from
1398 : : * ProcGlobal->xids[] again anyway; see GetNewTransactionId).
1399 : : */
1400 : : bool
7605 tgl@sss.pgh.pa.us 1401 : 7856381 : TransactionIdIsInProgress(TransactionId xid)
1402 : : {
1403 : : static TransactionId *xids = NULL;
1404 : : static TransactionId *other_xids;
1405 : : XidCacheStatus *other_subxidstates;
6750 1406 : 7856381 : int nxids = 0;
7605 1407 : 7856381 : ProcArrayStruct *arrayP = procArray;
1408 : : TransactionId topxid;
1409 : : TransactionId latestCompletedXid;
1410 : : int mypgxactoff;
1411 : : int numProcs;
1412 : : int j;
1413 : :
1414 : : /*
1415 : : * Don't bother checking a transaction older than RecentXmin; it could not
1416 : : * possibly still be running. (Note: in particular, this guarantees that
1417 : : * we reject InvalidTransactionId, FrozenTransactionId, etc as not
1418 : : * running.)
1419 : : */
1420 [ + + ]: 7856381 : if (TransactionIdPrecedes(xid, RecentXmin))
1421 : : {
1422 : : xc_by_recent_xmin_inc();
1423 : 5120663 : return false;
1424 : : }
1425 : :
1426 : : /*
1427 : : * We may have just checked the status of this transaction, so if it is
1428 : : * already known to be completed, we can fall out without any access to
1429 : : * shared memory.
1430 : : */
1357 heikki.linnakangas@i 1431 [ + + ]: 2735718 : if (TransactionIdEquals(cachedXidIsNotInProgress, xid))
1432 : : {
1433 : : xc_by_known_xact_inc();
6578 tgl@sss.pgh.pa.us 1434 : 1011630 : return false;
1435 : : }
1436 : :
1437 : : /*
1438 : : * Also, we can handle our own transaction (and subtransactions) without
1439 : : * any access to shared memory.
1440 : : */
6750 1441 [ + + ]: 1724088 : if (TransactionIdIsCurrentTransactionId(xid))
1442 : : {
1443 : : xc_by_my_xact_inc();
1444 : 198472 : return true;
1445 : : }
1446 : :
1447 : : /*
1448 : : * If first time through, get workspace to remember main XIDs in. We
1449 : : * malloc it permanently to avoid repeated palloc/pfree overhead.
1450 : : */
1451 [ + + ]: 1525616 : if (xids == NULL)
1452 : : {
1453 : : /*
1454 : : * In hot standby mode, reserve enough space to hold all xids in the
1455 : : * known-assigned list. If we later finish recovery, we no longer need
1456 : : * the bigger array, but we don't bother to shrink it.
1457 : : */
5800 1458 [ + + ]: 793 : int maxxids = RecoveryInProgress() ? TOTAL_MAX_CACHED_SUBXIDS : arrayP->maxProcs;
1459 : :
5930 simon@2ndQuadrant.co 1460 : 793 : xids = (TransactionId *) malloc(maxxids * sizeof(TransactionId));
6750 tgl@sss.pgh.pa.us 1461 [ - + ]: 793 : if (xids == NULL)
6750 tgl@sss.pgh.pa.us 1462 [ # # ]:UBC 0 : ereport(ERROR,
1463 : : (errcode(ERRCODE_OUT_OF_MEMORY),
1464 : : errmsg("out of memory")));
1465 : : }
1466 : :
2039 andres@anarazel.de 1467 :CBC 1525616 : other_xids = ProcGlobal->xids;
1468 : 1525616 : other_subxidstates = ProcGlobal->subxidStates;
1469 : :
7605 tgl@sss.pgh.pa.us 1470 : 1525616 : LWLockAcquire(ProcArrayLock, LW_SHARED);
1471 : :
1472 : : /*
1473 : : * Now that we have the lock, we can check latestCompletedXid; if the
1474 : : * target Xid is after that, it's surely still running.
1475 : : */
2042 andres@anarazel.de 1476 : 1525616 : latestCompletedXid =
828 heikki.linnakangas@i 1477 : 1525616 : XidFromFullTransactionId(TransamVariables->latestCompletedXid);
2042 andres@anarazel.de 1478 [ + + ]: 1525616 : if (TransactionIdPrecedes(latestCompletedXid, xid))
1479 : : {
6748 tgl@sss.pgh.pa.us 1480 : 1509130 : LWLockRelease(ProcArrayLock);
1481 : : xc_by_latest_xid_inc();
1482 : 1509130 : return true;
1483 : : }
1484 : :
1485 : : /* No shortcuts, gotta grovel through the array */
2039 andres@anarazel.de 1486 : 16486 : mypgxactoff = MyProc->pgxactoff;
1487 : 16486 : numProcs = arrayP->numProcs;
1641 fujii@postgresql.org 1488 [ + + ]: 168355 : for (int pgxactoff = 0; pgxactoff < numProcs; pgxactoff++)
1489 : : {
1490 : : int pgprocno;
1491 : : PGPROC *proc;
1492 : : TransactionId pxid;
1493 : : int pxids;
1494 : :
1495 : : /* Ignore ourselves --- dealt with it above */
2039 andres@anarazel.de 1496 [ + + ]: 155514 : if (pgxactoff == mypgxactoff)
6750 tgl@sss.pgh.pa.us 1497 : 14397 : continue;
1498 : :
1499 : : /* Fetch xid just once - see GetNewTransactionId */
2039 andres@anarazel.de 1500 : 141117 : pxid = UINT32_ACCESS_ONCE(other_xids[pgxactoff]);
1501 : :
7605 tgl@sss.pgh.pa.us 1502 [ + + ]: 141117 : if (!TransactionIdIsValid(pxid))
1503 : 87769 : continue;
1504 : :
1505 : : /*
1506 : : * Step 1: check the main Xid
1507 : : */
1508 [ + + ]: 53348 : if (TransactionIdEquals(pxid, xid))
1509 : : {
6750 1510 : 3500 : LWLockRelease(ProcArrayLock);
1511 : : xc_by_main_xid_inc();
1512 : 3500 : return true;
1513 : : }
1514 : :
1515 : : /*
1516 : : * We can ignore main Xids that are younger than the target Xid, since
1517 : : * the target could not possibly be their child.
1518 : : */
7605 1519 [ + + ]: 49848 : if (TransactionIdPrecedes(xid, pxid))
1520 : 26657 : continue;
1521 : :
1522 : : /*
1523 : : * Step 2: check the cached child-Xids arrays
1524 : : */
2039 andres@anarazel.de 1525 : 23191 : pxids = other_subxidstates[pgxactoff].count;
2683 1526 : 23191 : pg_read_barrier(); /* pairs with barrier in GetNewTransactionId() */
2039 1527 : 23191 : pgprocno = arrayP->pgprocnos[pgxactoff];
1528 : 23191 : proc = &allProcs[pgprocno];
2683 1529 [ + + ]: 38367 : for (j = pxids - 1; j >= 0; j--)
1530 : : {
1531 : : /* Fetch xid just once - see GetNewTransactionId */
1532 : 15321 : TransactionId cxid = UINT32_ACCESS_ONCE(proc->subxids.xids[j]);
1533 : :
7605 tgl@sss.pgh.pa.us 1534 [ + + ]: 15321 : if (TransactionIdEquals(cxid, xid))
1535 : : {
6750 1536 : 145 : LWLockRelease(ProcArrayLock);
1537 : : xc_by_child_xid_inc();
1538 : 145 : return true;
1539 : : }
1540 : : }
1541 : :
1542 : : /*
1543 : : * Save the main Xid for step 4. We only need to remember main Xids
1544 : : * that have uncached children. (Note: there is no race condition
1545 : : * here because the overflowed flag cannot be cleared, only set, while
1546 : : * we hold ProcArrayLock. So we can't miss an Xid that we need to
1547 : : * worry about.)
1548 : : */
2039 andres@anarazel.de 1549 [ + + ]: 23046 : if (other_subxidstates[pgxactoff].overflowed)
7605 tgl@sss.pgh.pa.us 1550 : 157 : xids[nxids++] = pxid;
1551 : : }
1552 : :
1553 : : /*
1554 : : * Step 3: in hot standby mode, check the known-assigned-xids list. XIDs
1555 : : * in the list must be treated as running.
1556 : : */
5930 simon@2ndQuadrant.co 1557 [ + + ]: 12841 : if (RecoveryInProgress())
1558 : : {
1559 : : /* none of the PGPROC entries should have XIDs in hot standby mode */
1560 [ - + ]: 1 : Assert(nxids == 0);
1561 : :
5800 tgl@sss.pgh.pa.us 1562 [ - + ]: 1 : if (KnownAssignedXidExists(xid))
1563 : : {
5930 simon@2ndQuadrant.co 1564 :UBC 0 : LWLockRelease(ProcArrayLock);
1565 : : xc_by_known_assigned_inc();
1566 : 0 : return true;
1567 : : }
1568 : :
1569 : : /*
1570 : : * If the KnownAssignedXids overflowed, we have to check pg_subtrans
1571 : : * too. Fetch all xids from KnownAssignedXids that are lower than
1572 : : * xid, since if xid is a subtransaction its parent will always have a
1573 : : * lower value. Note we will collect both main and subXIDs here, but
1574 : : * there's no help for it.
1575 : : */
5930 simon@2ndQuadrant.co 1576 [ - + ]:CBC 1 : if (TransactionIdPrecedesOrEquals(xid, procArray->lastOverflowedXid))
5930 simon@2ndQuadrant.co 1577 :UBC 0 : nxids = KnownAssignedXidsGet(xids, xid);
1578 : : }
1579 : :
7605 tgl@sss.pgh.pa.us 1580 :CBC 12841 : LWLockRelease(ProcArrayLock);
1581 : :
1582 : : /*
1583 : : * If none of the relevant caches overflowed, we know the Xid is not
1584 : : * running without even looking at pg_subtrans.
1585 : : */
1586 [ + + ]: 12841 : if (nxids == 0)
1587 : : {
1588 : : xc_no_overflow_inc();
1357 heikki.linnakangas@i 1589 : 12684 : cachedXidIsNotInProgress = xid;
6750 tgl@sss.pgh.pa.us 1590 : 12684 : return false;
1591 : : }
1592 : :
1593 : : /*
1594 : : * Step 4: have to check pg_subtrans.
1595 : : *
1596 : : * At this point, we know it's either a subtransaction of one of the Xids
1597 : : * in xids[], or it's not running. If it's an already-failed
1598 : : * subtransaction, we want to say "not running" even though its parent may
1599 : : * still be running. So first, check pg_xact to see if it's been aborted.
1600 : : */
1601 : : xc_slow_answer_inc();
1602 : :
7605 1603 [ - + ]: 157 : if (TransactionIdDidAbort(xid))
1604 : : {
1357 heikki.linnakangas@i 1605 :UBC 0 : cachedXidIsNotInProgress = xid;
6750 tgl@sss.pgh.pa.us 1606 : 0 : return false;
1607 : : }
1608 : :
1609 : : /*
1610 : : * It isn't aborted, so check whether the transaction tree it belongs to
1611 : : * is still running (or, more precisely, whether it was running when we
1612 : : * held ProcArrayLock).
1613 : : */
7605 tgl@sss.pgh.pa.us 1614 :CBC 157 : topxid = SubTransGetTopmostTransaction(xid);
1615 [ - + ]: 157 : Assert(TransactionIdIsValid(topxid));
1270 michael@paquier.xyz 1616 [ + - + - ]: 314 : if (!TransactionIdEquals(topxid, xid) &&
1617 : 157 : pg_lfind32(topxid, xids, nxids))
1618 : 157 : return true;
1619 : :
1357 heikki.linnakangas@i 1620 :UBC 0 : cachedXidIsNotInProgress = xid;
6750 tgl@sss.pgh.pa.us 1621 : 0 : return false;
1622 : : }
1623 : :
1624 : :
1625 : : /*
1626 : : * Determine XID horizons.
1627 : : *
1628 : : * This is used by wrapper functions like GetOldestNonRemovableTransactionId()
1629 : : * (for VACUUM), GetReplicationHorizons() (for hot_standby_feedback), etc as
1630 : : * well as "internally" by GlobalVisUpdate() (see comment above struct
1631 : : * GlobalVisState).
1632 : : *
1633 : : * See the definition of ComputeXidHorizonsResult for the various computed
1634 : : * horizons.
1635 : : *
1636 : : * For VACUUM separate horizons (used to decide which deleted tuples must
1637 : : * be preserved), for shared and non-shared tables are computed. For shared
1638 : : * relations backends in all databases must be considered, but for non-shared
1639 : : * relations that's not required, since only backends in my own database could
1640 : : * ever see the tuples in them. Also, we can ignore concurrently running lazy
1641 : : * VACUUMs because (a) they must be working on other tables, and (b) they
1642 : : * don't need to do snapshot-based lookups.
1643 : : *
1644 : : * This also computes a horizon used to truncate pg_subtrans. For that
1645 : : * backends in all databases have to be considered, and concurrently running
1646 : : * lazy VACUUMs cannot be ignored, as they still may perform pg_subtrans
1647 : : * accesses.
1648 : : *
1649 : : * Note: we include all currently running xids in the set of considered xids.
1650 : : * This ensures that if a just-started xact has not yet set its snapshot,
1651 : : * when it does set the snapshot it cannot set xmin less than what we compute.
1652 : : * See notes in src/backend/access/transam/README.
1653 : : *
1654 : : * Note: despite the above, it's possible for the calculated values to move
1655 : : * backwards on repeated calls. The calculated values are conservative, so
1656 : : * that anything older is definitely not considered as running by anyone
1657 : : * anymore, but the exact values calculated depend on a number of things. For
1658 : : * example, if there are no transactions running in the current database, the
1659 : : * horizon for normal tables will be latestCompletedXid. If a transaction
1660 : : * begins after that, its xmin will include in-progress transactions in other
1661 : : * databases that started earlier, so another call will return a lower value.
1662 : : * Nonetheless it is safe to vacuum a table in the current database with the
1663 : : * first result. There are also replication-related effects: a walsender
1664 : : * process can set its xmin based on transactions that are no longer running
1665 : : * on the primary but are still being replayed on the standby, thus possibly
1666 : : * making the values go backwards. In this case there is a possibility that
1667 : : * we lose data that the standby would like to have, but unless the standby
1668 : : * uses a replication slot to make its xmin persistent there is little we can
1669 : : * do about that --- data is only protected if the walsender runs continuously
1670 : : * while queries are executed on the standby. (The Hot Standby code deals
1671 : : * with such cases by failing standby queries that needed to access
1672 : : * already-removed data, so there's no integrity bug.)
1673 : : *
1674 : : * Note: the approximate horizons (see definition of GlobalVisState) are
1675 : : * updated by the computations done here. That's currently required for
1676 : : * correctness and a small optimization. Without doing so it's possible that
1677 : : * heap vacuum's call to heap_page_prune_and_freeze() uses a more conservative
1678 : : * horizon than later when deciding which tuples can be removed - which the
1679 : : * code doesn't expect (breaking HOT).
1680 : : */
1681 : : static void
2041 andres@anarazel.de 1682 :CBC 89137 : ComputeXidHorizons(ComputeXidHorizonsResult *h)
1683 : : {
7605 tgl@sss.pgh.pa.us 1684 : 89137 : ProcArrayStruct *arrayP = procArray;
1685 : : TransactionId kaxmin;
2041 andres@anarazel.de 1686 : 89137 : bool in_recovery = RecoveryInProgress();
2039 1687 : 89137 : TransactionId *other_xids = ProcGlobal->xids;
1688 : :
1689 : : /* inferred after ProcArrayLock is released */
1384 alvherre@alvh.no-ip. 1690 : 89137 : h->catalog_oldest_nonremovable = InvalidTransactionId;
1691 : :
6763 tgl@sss.pgh.pa.us 1692 : 89137 : LWLockAcquire(ProcArrayLock, LW_SHARED);
1693 : :
828 heikki.linnakangas@i 1694 : 89137 : h->latest_completed = TransamVariables->latestCompletedXid;
1695 : :
1696 : : /*
1697 : : * We initialize the MIN() calculation with latestCompletedXid + 1. This
1698 : : * is a lower bound for the XIDs that might appear in the ProcArray later,
1699 : : * and so protects us against overestimating the result due to future
1700 : : * additions.
1701 : : */
1702 : : {
1703 : : TransactionId initial;
1704 : :
2041 andres@anarazel.de 1705 : 89137 : initial = XidFromFullTransactionId(h->latest_completed);
1706 [ - + ]: 89137 : Assert(TransactionIdIsValid(initial));
1707 [ - + ]: 89137 : TransactionIdAdvance(initial);
1708 : :
1709 : 89137 : h->oldest_considered_running = initial;
1710 : 89137 : h->shared_oldest_nonremovable = initial;
1711 : 89137 : h->data_oldest_nonremovable = initial;
1712 : :
1713 : : /*
1714 : : * Only modifications made by this backend affect the horizon for
1715 : : * temporary relations. Instead of a check in each iteration of the
1716 : : * loop over all PGPROCs it is cheaper to just initialize to the
1717 : : * current top-level xid any.
1718 : : *
1719 : : * Without an assigned xid we could use a horizon as aggressive as
1720 : : * GetNewTransactionId(), but we can get away with the much cheaper
1721 : : * latestCompletedXid + 1: If this backend has no xid there, by
1722 : : * definition, can't be any newer changes in the temp table than
1723 : : * latestCompletedXid.
1724 : : */
1964 1725 [ + + ]: 89137 : if (TransactionIdIsValid(MyProc->xid))
1726 : 34166 : h->temp_oldest_nonremovable = MyProc->xid;
1727 : : else
1728 : 54971 : h->temp_oldest_nonremovable = initial;
1729 : : }
1730 : :
1731 : : /*
1732 : : * Fetch slot horizons while ProcArrayLock is held - the
1733 : : * LWLockAcquire/LWLockRelease are a barrier, ensuring this happens inside
1734 : : * the lock.
1735 : : */
2041 1736 : 89137 : h->slot_xmin = procArray->replication_slot_xmin;
1737 : 89137 : h->slot_catalog_xmin = procArray->replication_slot_catalog_xmin;
1738 : :
1739 [ + + ]: 522790 : for (int index = 0; index < arrayP->numProcs; index++)
1740 : : {
5026 bruce@momjian.us 1741 : 433653 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 1742 : 433653 : PGPROC *proc = &allProcs[pgprocno];
1945 alvherre@alvh.no-ip. 1743 : 433653 : int8 statusFlags = ProcGlobal->statusFlags[index];
1744 : : TransactionId xid;
1745 : : TransactionId xmin;
1746 : :
1747 : : /* Fetch xid just once - see GetNewTransactionId */
2037 andres@anarazel.de 1748 : 433653 : xid = UINT32_ACCESS_ONCE(other_xids[index]);
2040 1749 : 433653 : xmin = UINT32_ACCESS_ONCE(proc->xmin);
1750 : :
1751 : : /*
1752 : : * Consider both the transaction's Xmin, and its Xid.
1753 : : *
1754 : : * We must check both because a transaction might have an Xmin but not
1755 : : * (yet) an Xid; conversely, if it has an Xid, that could determine
1756 : : * some not-yet-set Xmin.
1757 : : */
2041 1758 : 433653 : xmin = TransactionIdOlder(xmin, xid);
1759 : :
1760 : : /* if neither is set, this proc doesn't influence the horizon */
2002 peter@eisentraut.org 1761 [ + + ]: 433653 : if (!TransactionIdIsValid(xmin))
7168 alvherre@alvh.no-ip. 1762 : 230486 : continue;
1763 : :
1764 : : /*
1765 : : * Don't ignore any procs when determining which transactions might be
1766 : : * considered running. While slots should ensure logical decoding
1767 : : * backends are protected even without this check, it can't hurt to
1768 : : * include them here as well..
1769 : : */
2041 andres@anarazel.de 1770 : 203167 : h->oldest_considered_running =
1771 : 203167 : TransactionIdOlder(h->oldest_considered_running, xmin);
1772 : :
1773 : : /*
1774 : : * Skip over backends either vacuuming (which is ok with rows being
1775 : : * removed, as long as pg_subtrans is not truncated) or doing logical
1776 : : * decoding (which manages xmin separately, check below).
1777 : : */
1945 alvherre@alvh.no-ip. 1778 [ + + ]: 203167 : if (statusFlags & (PROC_IN_VACUUM | PROC_IN_LOGICAL_DECODING))
2041 andres@anarazel.de 1779 : 15534 : continue;
1780 : :
1781 : : /* shared tables need to take backends in all databases into account */
1782 : 187633 : h->shared_oldest_nonremovable =
1783 : 187633 : TransactionIdOlder(h->shared_oldest_nonremovable, xmin);
1784 : :
1785 : : /*
1786 : : * Normally sessions in other databases are ignored for anything but
1787 : : * the shared horizon.
1788 : : *
1789 : : * However, include them when MyDatabaseId is not (yet) set. A
1790 : : * backend in the process of starting up must not compute a "too
1791 : : * aggressive" horizon, otherwise we could end up using it to prune
1792 : : * still-needed data away. If the current backend never connects to a
1793 : : * database this is harmless, because data_oldest_nonremovable will
1794 : : * never be utilized.
1795 : : *
1796 : : * Also, sessions marked with PROC_AFFECTS_ALL_HORIZONS should always
1797 : : * be included. (This flag is used for hot standby feedback, which
1798 : : * can't be tied to a specific database.)
1799 : : *
1800 : : * Also, while in recovery we cannot compute an accurate per-database
1801 : : * horizon, as all xids are managed via the KnownAssignedXids
1802 : : * machinery.
1803 : : */
1430 tgl@sss.pgh.pa.us 1804 [ + + ]: 187633 : if (proc->databaseId == MyDatabaseId ||
1805 [ + + ]: 8778 : MyDatabaseId == InvalidOid ||
1806 [ + + - + ]: 564 : (statusFlags & PROC_AFFECTS_ALL_HORIZONS) ||
1807 : : in_recovery)
1808 : : {
1384 alvherre@alvh.no-ip. 1809 : 187071 : h->data_oldest_nonremovable =
1810 : 187071 : TransactionIdOlder(h->data_oldest_nonremovable, xmin);
1811 : : }
1812 : : }
1813 : :
1814 : : /*
1815 : : * If in recovery fetch oldest xid in KnownAssignedXids, will be applied
1816 : : * after lock is released.
1817 : : */
2041 andres@anarazel.de 1818 [ + + ]: 89137 : if (in_recovery)
1819 : 365 : kaxmin = KnownAssignedXidsGetOldestXmin();
1820 : :
1821 : : /*
1822 : : * No other information from shared state is needed, release the lock
1823 : : * immediately. The rest of the computations can be done without a lock.
1824 : : */
1825 : 89137 : LWLockRelease(ProcArrayLock);
1826 : :
1827 [ + + ]: 89137 : if (in_recovery)
1828 : : {
1829 : 365 : h->oldest_considered_running =
1830 : 365 : TransactionIdOlder(h->oldest_considered_running, kaxmin);
1831 : 365 : h->shared_oldest_nonremovable =
1832 : 365 : TransactionIdOlder(h->shared_oldest_nonremovable, kaxmin);
1833 : 365 : h->data_oldest_nonremovable =
1834 : 365 : TransactionIdOlder(h->data_oldest_nonremovable, kaxmin);
1835 : : /* temp relations cannot be accessed in recovery */
1836 : : }
1837 : :
1056 1838 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1839 : : h->shared_oldest_nonremovable));
1840 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->shared_oldest_nonremovable,
1841 : : h->data_oldest_nonremovable));
1842 : :
1843 : : /*
1844 : : * Check whether there are replication slots requiring an older xmin.
1845 : : */
2041 1846 : 89137 : h->shared_oldest_nonremovable =
1847 : 89137 : TransactionIdOlder(h->shared_oldest_nonremovable, h->slot_xmin);
1848 : 89137 : h->data_oldest_nonremovable =
1849 : 89137 : TransactionIdOlder(h->data_oldest_nonremovable, h->slot_xmin);
1850 : :
1851 : : /*
1852 : : * The only difference between catalog / data horizons is that the slot's
1853 : : * catalog xmin is applied to the catalog one (so catalogs can be accessed
1854 : : * for logical decoding). Initialize with data horizon, and then back up
1855 : : * further if necessary. Have to back up the shared horizon as well, since
1856 : : * that also can contain catalogs.
1857 : : */
1858 : 89137 : h->shared_oldest_nonremovable_raw = h->shared_oldest_nonremovable;
1859 : 89137 : h->shared_oldest_nonremovable =
1860 : 89137 : TransactionIdOlder(h->shared_oldest_nonremovable,
1861 : : h->slot_catalog_xmin);
1384 alvherre@alvh.no-ip. 1862 : 89137 : h->catalog_oldest_nonremovable = h->data_oldest_nonremovable;
2041 andres@anarazel.de 1863 : 89137 : h->catalog_oldest_nonremovable =
1864 : 89137 : TransactionIdOlder(h->catalog_oldest_nonremovable,
1865 : : h->slot_catalog_xmin);
1866 : :
1867 : : /*
1868 : : * It's possible that slots backed up the horizons further than
1869 : : * oldest_considered_running. Fix.
1870 : : */
1871 : 89137 : h->oldest_considered_running =
1872 : 89137 : TransactionIdOlder(h->oldest_considered_running,
1873 : : h->shared_oldest_nonremovable);
1874 : 89137 : h->oldest_considered_running =
1875 : 89137 : TransactionIdOlder(h->oldest_considered_running,
1876 : : h->catalog_oldest_nonremovable);
1877 : 89137 : h->oldest_considered_running =
1878 : 89137 : TransactionIdOlder(h->oldest_considered_running,
1879 : : h->data_oldest_nonremovable);
1880 : :
1881 : : /*
1882 : : * shared horizons have to be at least as old as the oldest visible in
1883 : : * current db
1884 : : */
1885 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->shared_oldest_nonremovable,
1886 : : h->data_oldest_nonremovable));
1887 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->shared_oldest_nonremovable,
1888 : : h->catalog_oldest_nonremovable));
1889 : :
1890 : : /*
1891 : : * Horizons need to ensure that pg_subtrans access is still possible for
1892 : : * the relevant backends.
1893 : : */
1894 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1895 : : h->shared_oldest_nonremovable));
1896 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1897 : : h->catalog_oldest_nonremovable));
1898 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1899 : : h->data_oldest_nonremovable));
1964 1900 [ - + ]: 89137 : Assert(TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1901 : : h->temp_oldest_nonremovable));
2041 1902 [ + + - + ]: 89137 : Assert(!TransactionIdIsValid(h->slot_xmin) ||
1903 : : TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1904 : : h->slot_xmin));
1905 [ + + - + ]: 89137 : Assert(!TransactionIdIsValid(h->slot_catalog_xmin) ||
1906 : : TransactionIdPrecedesOrEquals(h->oldest_considered_running,
1907 : : h->slot_catalog_xmin));
1908 : :
1909 : : /* update approximate horizons with the computed horizons */
1910 : 89137 : GlobalVisUpdateApply(h);
1911 : 89137 : }
1912 : :
1913 : : /*
1914 : : * Determine what kind of visibility horizon needs to be used for a
1915 : : * relation. If rel is NULL, the most conservative horizon is used.
1916 : : */
1917 : : static inline GlobalVisHorizonKind
1695 1918 : 14366852 : GlobalVisHorizonKindForRel(Relation rel)
1919 : : {
1920 : : /*
1921 : : * Other relkinds currently don't contain xids, nor always the necessary
1922 : : * logical decoding markers.
1923 : : */
1924 [ + + + + : 14366852 : Assert(!rel ||
+ + - + ]
1925 : : rel->rd_rel->relkind == RELKIND_RELATION ||
1926 : : rel->rd_rel->relkind == RELKIND_MATVIEW ||
1927 : : rel->rd_rel->relkind == RELKIND_TOASTVALUE);
1928 : :
1929 [ + + + + : 14366852 : if (rel == NULL || rel->rd_rel->relisshared || RecoveryInProgress())
+ + ]
1930 : 74582 : return VISHORIZON_SHARED;
1931 [ + + ]: 14292270 : else if (IsCatalogRelation(rel) ||
1932 [ + + - + : 11359838 : RelationIsAccessibleInLogicalDecoding(rel))
+ + - + -
- - - + -
+ + - + -
- + - ]
1933 : 2932436 : return VISHORIZON_CATALOG;
1934 [ + + + + ]: 11359834 : else if (!RELATION_IS_LOCAL(rel))
1935 : 11305435 : return VISHORIZON_DATA;
1936 : : else
1937 : 54399 : return VISHORIZON_TEMP;
1938 : : }
1939 : :
1940 : : /*
1941 : : * Return the oldest XID for which deleted tuples must be preserved in the
1942 : : * passed table.
1943 : : *
1944 : : * If rel is not NULL the horizon may be considerably more recent than
1945 : : * otherwise (i.e. fewer tuples will be removable). In the NULL case a horizon
1946 : : * that is correct (but not optimal) for all relations will be returned.
1947 : : *
1948 : : * This is used by VACUUM to decide which deleted tuples must be preserved in
1949 : : * the passed in table.
1950 : : */
1951 : : TransactionId
2041 1952 : 35964 : GetOldestNonRemovableTransactionId(Relation rel)
1953 : : {
1954 : : ComputeXidHorizonsResult horizons;
1955 : :
1956 : 35964 : ComputeXidHorizons(&horizons);
1957 : :
1695 1958 [ + + + + : 35964 : switch (GlobalVisHorizonKindForRel(rel))
- ]
1959 : : {
1960 : 3402 : case VISHORIZON_SHARED:
1961 : 3402 : return horizons.shared_oldest_nonremovable;
1962 : 10680 : case VISHORIZON_CATALOG:
1963 : 10680 : return horizons.catalog_oldest_nonremovable;
1964 : 9446 : case VISHORIZON_DATA:
1965 : 9446 : return horizons.data_oldest_nonremovable;
1966 : 12436 : case VISHORIZON_TEMP:
1967 : 12436 : return horizons.temp_oldest_nonremovable;
1968 : : }
1969 : :
1970 : : /* just to prevent compiler warnings */
1695 andres@anarazel.de 1971 :UBC 0 : return InvalidTransactionId;
1972 : : }
1973 : :
1974 : : /*
1975 : : * Return the oldest transaction id any currently running backend might still
1976 : : * consider running. This should not be used for visibility / pruning
1977 : : * determinations (see GetOldestNonRemovableTransactionId()), but for
1978 : : * decisions like up to where pg_subtrans can be truncated.
1979 : : */
1980 : : TransactionId
2041 andres@anarazel.de 1981 :CBC 1772 : GetOldestTransactionIdConsideredRunning(void)
1982 : : {
1983 : : ComputeXidHorizonsResult horizons;
1984 : :
1985 : 1772 : ComputeXidHorizons(&horizons);
1986 : :
1987 : 1772 : return horizons.oldest_considered_running;
1988 : : }
1989 : :
1990 : : /*
1991 : : * Return the visibility horizons for a hot standby feedback message.
1992 : : */
1993 : : void
1994 : 49 : GetReplicationHorizons(TransactionId *xmin, TransactionId *catalog_xmin)
1995 : : {
1996 : : ComputeXidHorizonsResult horizons;
1997 : :
1998 : 49 : ComputeXidHorizons(&horizons);
1999 : :
2000 : : /*
2001 : : * Don't want to use shared_oldest_nonremovable here, as that contains the
2002 : : * effect of replication slot's catalog_xmin. We want to send a separate
2003 : : * feedback for the catalog horizon, so the primary can remove data table
2004 : : * contents more aggressively.
2005 : : */
2006 : 49 : *xmin = horizons.shared_oldest_nonremovable_raw;
2007 : 49 : *catalog_xmin = horizons.slot_catalog_xmin;
7605 tgl@sss.pgh.pa.us 2008 : 49 : }
2009 : :
2010 : : /*
2011 : : * GetMaxSnapshotXidCount -- get max size for snapshot XID array
2012 : : *
2013 : : * We have to export this for use by snapmgr.c.
2014 : : */
2015 : : int
5258 2016 : 34188 : GetMaxSnapshotXidCount(void)
2017 : : {
2018 : 34188 : return procArray->maxProcs;
2019 : : }
2020 : :
2021 : : /*
2022 : : * GetMaxSnapshotSubxidCount -- get max size for snapshot sub-XID array
2023 : : *
2024 : : * We have to export this for use by snapmgr.c.
2025 : : */
2026 : : int
2027 : 33990 : GetMaxSnapshotSubxidCount(void)
2028 : : {
2029 : 33990 : return TOTAL_MAX_CACHED_SUBXIDS;
2030 : : }
2031 : :
2032 : : /*
2033 : : * Helper function for GetSnapshotData() that checks if the bulk of the
2034 : : * visibility information in the snapshot is still valid. If so, it updates
2035 : : * the fields that need to change and returns true. Otherwise it returns
2036 : : * false.
2037 : : *
2038 : : * This very likely can be evolved to not need ProcArrayLock held (at very
2039 : : * least in the case we already hold a snapshot), but that's for another day.
2040 : : */
2041 : : static bool
2036 andres@anarazel.de 2042 : 2309698 : GetSnapshotDataReuse(Snapshot snapshot)
2043 : : {
2044 : : uint64 curXactCompletionCount;
2045 : :
2046 [ - + ]: 2309698 : Assert(LWLockHeldByMe(ProcArrayLock));
2047 : :
2048 [ + + ]: 2309698 : if (unlikely(snapshot->snapXactCompletionCount == 0))
2049 : 32255 : return false;
2050 : :
828 heikki.linnakangas@i 2051 : 2277443 : curXactCompletionCount = TransamVariables->xactCompletionCount;
2036 andres@anarazel.de 2052 [ + + ]: 2277443 : if (curXactCompletionCount != snapshot->snapXactCompletionCount)
2053 : 367251 : return false;
2054 : :
2055 : : /*
2056 : : * If the current xactCompletionCount is still the same as it was at the
2057 : : * time the snapshot was built, we can be sure that rebuilding the
2058 : : * contents of the snapshot the hard way would result in the same snapshot
2059 : : * contents:
2060 : : *
2061 : : * As explained in transam/README, the set of xids considered running by
2062 : : * GetSnapshotData() cannot change while ProcArrayLock is held. Snapshot
2063 : : * contents only depend on transactions with xids and xactCompletionCount
2064 : : * is incremented whenever a transaction with an xid finishes (while
2065 : : * holding ProcArrayLock exclusively). Thus the xactCompletionCount check
2066 : : * ensures we would detect if the snapshot would have changed.
2067 : : *
2068 : : * As the snapshot contents are the same as it was before, it is safe to
2069 : : * re-enter the snapshot's xmin into the PGPROC array. None of the rows
2070 : : * visible under the snapshot could already have been removed (that'd
2071 : : * require the set of running transactions to change) and it fulfills the
2072 : : * requirement that concurrent GetSnapshotData() calls yield the same
2073 : : * xmin.
2074 : : */
2075 [ + + ]: 1910192 : if (!TransactionIdIsValid(MyProc->xmin))
2076 : 491419 : MyProc->xmin = TransactionXmin = snapshot->xmin;
2077 : :
2078 : 1910192 : RecentXmin = snapshot->xmin;
2079 [ - + ]: 1910192 : Assert(TransactionIdPrecedesOrEquals(TransactionXmin, RecentXmin));
2080 : :
2081 : 1910192 : snapshot->curcid = GetCurrentCommandId(false);
2082 : 1910192 : snapshot->active_count = 0;
2083 : 1910192 : snapshot->regd_count = 0;
2084 : 1910192 : snapshot->copied = false;
2085 : :
2086 : 1910192 : return true;
2087 : : }
2088 : :
2089 : : /*
2090 : : * GetSnapshotData -- returns information about running transactions.
2091 : : *
2092 : : * The returned snapshot includes xmin (lowest still-running xact ID),
2093 : : * xmax (highest completed xact ID + 1), and a list of running xact IDs
2094 : : * in the range xmin <= xid < xmax. It is used as follows:
2095 : : * All xact IDs < xmin are considered finished.
2096 : : * All xact IDs >= xmax are considered still running.
2097 : : * For an xact ID xmin <= xid < xmax, consult list to see whether
2098 : : * it is considered running or not.
2099 : : * This ensures that the set of transactions seen as "running" by the
2100 : : * current xact will not change after it takes the snapshot.
2101 : : *
2102 : : * All running top-level XIDs are included in the snapshot, except for lazy
2103 : : * VACUUM processes. We also try to include running subtransaction XIDs,
2104 : : * but since PGPROC has only a limited cache area for subxact XIDs, full
2105 : : * information may not be available. If we find any overflowed subxid arrays,
2106 : : * we have to mark the snapshot's subxid data as overflowed, and extra work
2107 : : * *may* need to be done to determine what's running (see XidInMVCCSnapshot()).
2108 : : *
2109 : : * We also update the following backend-global variables:
2110 : : * TransactionXmin: the oldest xmin of any snapshot in use in the
2111 : : * current transaction (this is the same as MyProc->xmin).
2112 : : * RecentXmin: the xmin computed for the most recent snapshot. XIDs
2113 : : * older than this are known not running any more.
2114 : : *
2115 : : * And try to advance the bounds of GlobalVis{Shared,Catalog,Data,Temp}Rels
2116 : : * for the benefit of the GlobalVisTest* family of functions.
2117 : : *
2118 : : * Note: this function should probably not be called with an argument that's
2119 : : * not statically allocated (see xip allocation below).
2120 : : */
2121 : : Snapshot
6516 alvherre@alvh.no-ip. 2122 : 2309698 : GetSnapshotData(Snapshot snapshot)
2123 : : {
7605 tgl@sss.pgh.pa.us 2124 : 2309698 : ProcArrayStruct *arrayP = procArray;
2039 andres@anarazel.de 2125 : 2309698 : TransactionId *other_xids = ProcGlobal->xids;
2126 : : TransactionId xmin;
2127 : : TransactionId xmax;
1641 fujii@postgresql.org 2128 : 2309698 : int count = 0;
7133 tgl@sss.pgh.pa.us 2129 : 2309698 : int subcount = 0;
5930 simon@2ndQuadrant.co 2130 : 2309698 : bool suboverflowed = false;
2131 : : FullTransactionId latest_completed;
2132 : : TransactionId oldestxid;
2133 : : int mypgxactoff;
2134 : : TransactionId myxid;
2135 : : uint64 curXactCompletionCount;
2136 : :
2683 andres@anarazel.de 2137 : 2309698 : TransactionId replication_slot_xmin = InvalidTransactionId;
2138 : 2309698 : TransactionId replication_slot_catalog_xmin = InvalidTransactionId;
2139 : :
7605 tgl@sss.pgh.pa.us 2140 [ - + ]: 2309698 : Assert(snapshot != NULL);
2141 : :
2142 : : /*
2143 : : * Allocating space for maxProcs xids is usually overkill; numProcs would
2144 : : * be sufficient. But it seems better to do the malloc while not holding
2145 : : * the lock, so we can't look at numProcs. Likewise, we allocate much
2146 : : * more subxip storage than is probably needed.
2147 : : *
2148 : : * This does open a possibility for avoiding repeated malloc/free: since
2149 : : * maxProcs does not change at runtime, we can simply reuse the previous
2150 : : * xip arrays if any. (This relies on the fact that all callers pass
2151 : : * static SnapshotData structs.)
2152 : : */
2153 [ + + ]: 2309698 : if (snapshot->xip == NULL)
2154 : : {
2155 : : /*
2156 : : * First call for this snapshot. Snapshot is same size whether or not
2157 : : * we are in recovery, see later comments.
2158 : : */
2159 : 32246 : snapshot->xip = (TransactionId *)
5258 2160 : 32246 : malloc(GetMaxSnapshotXidCount() * sizeof(TransactionId));
7605 2161 [ - + ]: 32246 : if (snapshot->xip == NULL)
7605 tgl@sss.pgh.pa.us 2162 [ # # ]:UBC 0 : ereport(ERROR,
2163 : : (errcode(ERRCODE_OUT_OF_MEMORY),
2164 : : errmsg("out of memory")));
7133 tgl@sss.pgh.pa.us 2165 [ - + ]:CBC 32246 : Assert(snapshot->subxip == NULL);
2166 : 32246 : snapshot->subxip = (TransactionId *)
5258 2167 : 32246 : malloc(GetMaxSnapshotSubxidCount() * sizeof(TransactionId));
7133 2168 [ - + ]: 32246 : if (snapshot->subxip == NULL)
7133 tgl@sss.pgh.pa.us 2169 [ # # ]:UBC 0 : ereport(ERROR,
2170 : : (errcode(ERRCODE_OUT_OF_MEMORY),
2171 : : errmsg("out of memory")));
2172 : : }
2173 : :
2174 : : /*
2175 : : * It is sufficient to get shared lock on ProcArrayLock, even if we are
2176 : : * going to set MyProc->xmin.
2177 : : */
7133 tgl@sss.pgh.pa.us 2178 :CBC 2309698 : LWLockAcquire(ProcArrayLock, LW_SHARED);
2179 : :
2036 andres@anarazel.de 2180 [ + + ]: 2309698 : if (GetSnapshotDataReuse(snapshot))
2181 : : {
2182 : 1910192 : LWLockRelease(ProcArrayLock);
2183 : 1910192 : return snapshot;
2184 : : }
2185 : :
828 heikki.linnakangas@i 2186 : 399506 : latest_completed = TransamVariables->latestCompletedXid;
2039 andres@anarazel.de 2187 : 399506 : mypgxactoff = MyProc->pgxactoff;
2188 : 399506 : myxid = other_xids[mypgxactoff];
2189 [ - + ]: 399506 : Assert(myxid == MyProc->xid);
2190 : :
828 heikki.linnakangas@i 2191 : 399506 : oldestxid = TransamVariables->oldestXid;
2192 : 399506 : curXactCompletionCount = TransamVariables->xactCompletionCount;
2193 : :
2194 : : /* xmax is always latestCompletedXid + 1 */
2042 andres@anarazel.de 2195 : 399506 : xmax = XidFromFullTransactionId(latest_completed);
6763 tgl@sss.pgh.pa.us 2196 [ - + ]: 399506 : TransactionIdAdvance(xmax);
2042 andres@anarazel.de 2197 [ - + ]: 399506 : Assert(TransactionIdIsNormal(xmax));
2198 : :
2199 : : /* initialize xmin calculation with xmax */
2041 2200 : 399506 : xmin = xmax;
2201 : :
2202 : : /* take own xid into account, saves a check inside the loop */
2039 2203 [ + + + - : 399506 : if (TransactionIdIsNormal(myxid) && NormalTransactionIdPrecedes(myxid, xmin))
- + + + ]
2204 : 34918 : xmin = myxid;
2205 : :
5809 simon@2ndQuadrant.co 2206 : 399506 : snapshot->takenDuringRecovery = RecoveryInProgress();
2207 : :
5810 2208 [ + + ]: 399506 : if (!snapshot->takenDuringRecovery)
2209 : : {
1641 fujii@postgresql.org 2210 : 398238 : int numProcs = arrayP->numProcs;
2039 andres@anarazel.de 2211 : 398238 : TransactionId *xip = snapshot->xip;
5026 bruce@momjian.us 2212 : 398238 : int *pgprocnos = arrayP->pgprocnos;
2039 andres@anarazel.de 2213 : 398238 : XidCacheStatus *subxidStates = ProcGlobal->subxidStates;
1945 alvherre@alvh.no-ip. 2214 : 398238 : uint8 *allStatusFlags = ProcGlobal->statusFlags;
2215 : :
2216 : : /*
2217 : : * First collect set of pgxactoff/xids that need to be included in the
2218 : : * snapshot.
2219 : : */
1641 fujii@postgresql.org 2220 [ + + ]: 3624926 : for (int pgxactoff = 0; pgxactoff < numProcs; pgxactoff++)
2221 : : {
2222 : : /* Fetch xid just once - see GetNewTransactionId */
2039 andres@anarazel.de 2223 : 3226688 : TransactionId xid = UINT32_ACCESS_ONCE(other_xids[pgxactoff]);
2224 : : uint8 statusFlags;
2225 : :
2226 [ - + ]: 3226688 : Assert(allProcs[arrayP->pgprocnos[pgxactoff]].pgxactoff == pgxactoff);
2227 : :
2228 : : /*
2229 : : * If the transaction has no XID assigned, we can skip it; it
2230 : : * won't have sub-XIDs either.
2231 : : */
2232 [ + + ]: 3226688 : if (likely(xid == InvalidTransactionId))
6766 tgl@sss.pgh.pa.us 2233 : 2319765 : continue;
2234 : :
2235 : : /*
2236 : : * We don't include our own XIDs (if any) in the snapshot. It
2237 : : * needs to be included in the xmin computation, but we did so
2238 : : * outside the loop.
2239 : : */
2039 andres@anarazel.de 2240 [ + + ]: 906923 : if (pgxactoff == mypgxactoff)
2241 : 62038 : continue;
2242 : :
2243 : : /*
2244 : : * The only way we are able to get here with a non-normal xid is
2245 : : * during bootstrap - with this backend using
2246 : : * BootstrapTransactionId. But the above test should filter that
2247 : : * out.
2248 : : */
2249 [ - + ]: 844885 : Assert(TransactionIdIsNormal(xid));
2250 : :
2251 : : /*
2252 : : * If the XID is >= xmax, we can skip it; such transactions will
2253 : : * be treated as running anyway (and any sub-XIDs will also be >=
2254 : : * xmax).
2255 : : */
2256 [ + - - + : 844885 : if (!NormalTransactionIdPrecedes(xid, xmax))
+ + ]
5026 bruce@momjian.us 2257 : 220421 : continue;
2258 : :
2259 : : /*
2260 : : * Skip over backends doing logical decoding which manages xmin
2261 : : * separately (check below) and ones running LAZY VACUUM.
2262 : : */
1945 alvherre@alvh.no-ip. 2263 : 624464 : statusFlags = allStatusFlags[pgxactoff];
2264 [ + + ]: 624464 : if (statusFlags & (PROC_IN_LOGICAL_DECODING | PROC_IN_VACUUM))
2039 andres@anarazel.de 2265 : 17 : continue;
2266 : :
5203 rhaas@postgresql.org 2267 [ + - - + : 624447 : if (NormalTransactionIdPrecedes(xid, xmin))
+ + ]
2268 : 327923 : xmin = xid;
2269 : :
2270 : : /* Add XID to snapshot. */
2039 andres@anarazel.de 2271 : 624447 : xip[count++] = xid;
2272 : :
2273 : : /*
2274 : : * Save subtransaction XIDs if possible (if we've already
2275 : : * overflowed, there's no point). Note that the subxact XIDs must
2276 : : * be later than their parent, so no need to check them against
2277 : : * xmin. We could filter against xmax, but it seems better not to
2278 : : * do that much work while holding the ProcArrayLock.
2279 : : *
2280 : : * The other backend can add more subxids concurrently, but cannot
2281 : : * remove any. Hence it's important to fetch nxids just once.
2282 : : * Should be safe to use memcpy, though. (We needn't worry about
2283 : : * missing any xids added concurrently, because they must postdate
2284 : : * xmax.)
2285 : : *
2286 : : * Again, our own XIDs are not included in the snapshot.
2287 : : */
5203 rhaas@postgresql.org 2288 [ + + ]: 624447 : if (!suboverflowed)
2289 : : {
2290 : :
2039 andres@anarazel.de 2291 [ + + ]: 624443 : if (subxidStates[pgxactoff].overflowed)
5810 simon@2ndQuadrant.co 2292 : 20 : suboverflowed = true;
2293 : : else
2294 : : {
2039 andres@anarazel.de 2295 : 624423 : int nsubxids = subxidStates[pgxactoff].count;
2296 : :
2297 [ + + ]: 624423 : if (nsubxids > 0)
2298 : : {
2299 : 6379 : int pgprocno = pgprocnos[pgxactoff];
2683 2300 : 6379 : PGPROC *proc = &allProcs[pgprocno];
2301 : :
2302 : 6379 : pg_read_barrier(); /* pairs with GetNewTransactionId */
2303 : :
5810 simon@2ndQuadrant.co 2304 : 6379 : memcpy(snapshot->subxip + subcount,
1132 peter@eisentraut.org 2305 : 6379 : proc->subxids.xids,
2306 : : nsubxids * sizeof(TransactionId));
2039 andres@anarazel.de 2307 : 6379 : subcount += nsubxids;
2308 : : }
2309 : : }
2310 : : }
2311 : : }
2312 : : }
2313 : : else
2314 : : {
2315 : : /*
2316 : : * We're in hot standby, so get XIDs from KnownAssignedXids.
2317 : : *
2318 : : * We store all xids directly into subxip[]. Here's why:
2319 : : *
2320 : : * In recovery we don't know which xids are top-level and which are
2321 : : * subxacts, a design choice that greatly simplifies xid processing.
2322 : : *
2323 : : * It seems like we would want to try to put xids into xip[] only, but
2324 : : * that is fairly small. We would either need to make that bigger or
2325 : : * to increase the rate at which we WAL-log xid assignment; neither is
2326 : : * an appealing choice.
2327 : : *
2328 : : * We could try to store xids into xip[] first and then into subxip[]
2329 : : * if there are too many xids. That only works if the snapshot doesn't
2330 : : * overflow because we do not search subxip[] in that case. A simpler
2331 : : * way is to just store all xids in the subxip array because this is
2332 : : * by far the bigger array. We just leave the xip array empty.
2333 : : *
2334 : : * Either way we need to change the way XidInMVCCSnapshot() works
2335 : : * depending upon when the snapshot was taken, or change normal
2336 : : * snapshot processing so it matches.
2337 : : *
2338 : : * Note: It is possible for recovery to end before we finish taking
2339 : : * the snapshot, and for newly assigned transaction ids to be added to
2340 : : * the ProcArray. xmax cannot change while we hold ProcArrayLock, so
2341 : : * those newly added transaction ids would be filtered away, so we
2342 : : * need not be concerned about them.
2343 : : */
5800 tgl@sss.pgh.pa.us 2344 : 1268 : subcount = KnownAssignedXidsGetAndSetXmin(snapshot->subxip, &xmin,
2345 : : xmax);
2346 : :
2347 [ + + ]: 1268 : if (TransactionIdPrecedesOrEquals(xmin, procArray->lastOverflowedXid))
5930 simon@2ndQuadrant.co 2348 : 6 : suboverflowed = true;
2349 : : }
2350 : :
2351 : :
2352 : : /*
2353 : : * Fetch into local variable while ProcArrayLock is held - the
2354 : : * LWLockRelease below is a barrier, ensuring this happens inside the
2355 : : * lock.
2356 : : */
4426 rhaas@postgresql.org 2357 : 399506 : replication_slot_xmin = procArray->replication_slot_xmin;
4395 2358 : 399506 : replication_slot_catalog_xmin = procArray->replication_slot_catalog_xmin;
2359 : :
2040 andres@anarazel.de 2360 [ + + ]: 399506 : if (!TransactionIdIsValid(MyProc->xmin))
2361 : 212017 : MyProc->xmin = TransactionXmin = xmin;
2362 : :
7605 tgl@sss.pgh.pa.us 2363 : 399506 : LWLockRelease(ProcArrayLock);
2364 : :
2365 : : /* maintain state for GlobalVis* */
2366 : : {
2367 : : TransactionId def_vis_xid;
2368 : : TransactionId def_vis_xid_data;
2369 : : FullTransactionId def_vis_fxid;
2370 : : FullTransactionId def_vis_fxid_data;
2371 : : FullTransactionId oldestfxid;
2372 : :
2373 : : /*
2374 : : * Converting oldestXid is only safe when xid horizon cannot advance,
2375 : : * i.e. holding locks. While we don't hold the lock anymore, all the
2376 : : * necessary data has been gathered with lock held.
2377 : : */
2041 andres@anarazel.de 2378 : 399506 : oldestfxid = FullXidRelativeTo(latest_completed, oldestxid);
2379 : :
2380 : : /* Check whether there's a replication slot requiring an older xmin. */
2381 : : def_vis_xid_data =
1056 2382 : 399506 : TransactionIdOlder(xmin, replication_slot_xmin);
2383 : :
2384 : : /*
2385 : : * Rows in non-shared, non-catalog tables possibly could be vacuumed
2386 : : * if older than this xid.
2387 : : */
2041 2388 : 399506 : def_vis_xid = def_vis_xid_data;
2389 : :
2390 : : /*
2391 : : * Check whether there's a replication slot requiring an older catalog
2392 : : * xmin.
2393 : : */
2394 : : def_vis_xid =
2395 : 399506 : TransactionIdOlder(replication_slot_catalog_xmin, def_vis_xid);
2396 : :
2397 : 399506 : def_vis_fxid = FullXidRelativeTo(latest_completed, def_vis_xid);
2398 : 399506 : def_vis_fxid_data = FullXidRelativeTo(latest_completed, def_vis_xid_data);
2399 : :
2400 : : /*
2401 : : * Check if we can increase upper bound. As a previous
2402 : : * GlobalVisUpdate() might have computed more aggressive values, don't
2403 : : * overwrite them if so.
2404 : : */
2405 : : GlobalVisSharedRels.definitely_needed =
2406 : 399506 : FullTransactionIdNewer(def_vis_fxid,
2407 : : GlobalVisSharedRels.definitely_needed);
2408 : : GlobalVisCatalogRels.definitely_needed =
2409 : 399506 : FullTransactionIdNewer(def_vis_fxid,
2410 : : GlobalVisCatalogRels.definitely_needed);
2411 : : GlobalVisDataRels.definitely_needed =
2412 : 399506 : FullTransactionIdNewer(def_vis_fxid_data,
2413 : : GlobalVisDataRels.definitely_needed);
2414 : : /* See temp_oldest_nonremovable computation in ComputeXidHorizons() */
1964 2415 [ + + ]: 399506 : if (TransactionIdIsNormal(myxid))
2416 : : GlobalVisTempRels.definitely_needed =
2417 : 61936 : FullXidRelativeTo(latest_completed, myxid);
2418 : : else
2419 : : {
2420 : 337570 : GlobalVisTempRels.definitely_needed = latest_completed;
2421 : 337570 : FullTransactionIdAdvance(&GlobalVisTempRels.definitely_needed);
2422 : : }
2423 : :
2424 : : /*
2425 : : * Check if we know that we can initialize or increase the lower
2426 : : * bound. Currently the only cheap way to do so is to use
2427 : : * TransamVariables->oldestXid as input.
2428 : : *
2429 : : * We should definitely be able to do better. We could e.g. put a
2430 : : * global lower bound value into TransamVariables.
2431 : : */
2432 : : GlobalVisSharedRels.maybe_needed =
2041 2433 : 399506 : FullTransactionIdNewer(GlobalVisSharedRels.maybe_needed,
2434 : : oldestfxid);
2435 : : GlobalVisCatalogRels.maybe_needed =
2436 : 399506 : FullTransactionIdNewer(GlobalVisCatalogRels.maybe_needed,
2437 : : oldestfxid);
2438 : : GlobalVisDataRels.maybe_needed =
2439 : 399506 : FullTransactionIdNewer(GlobalVisDataRels.maybe_needed,
2440 : : oldestfxid);
2441 : : /* accurate value known */
1964 2442 : 399506 : GlobalVisTempRels.maybe_needed = GlobalVisTempRels.definitely_needed;
2443 : : }
2444 : :
7605 tgl@sss.pgh.pa.us 2445 : 399506 : RecentXmin = xmin;
2039 andres@anarazel.de 2446 [ - + ]: 399506 : Assert(TransactionIdPrecedesOrEquals(TransactionXmin, RecentXmin));
2447 : :
7605 tgl@sss.pgh.pa.us 2448 : 399506 : snapshot->xmin = xmin;
2449 : 399506 : snapshot->xmax = xmax;
2450 : 399506 : snapshot->xcnt = count;
7133 2451 : 399506 : snapshot->subxcnt = subcount;
5930 simon@2ndQuadrant.co 2452 : 399506 : snapshot->suboverflowed = suboverflowed;
2036 andres@anarazel.de 2453 : 399506 : snapshot->snapXactCompletionCount = curXactCompletionCount;
2454 : :
6680 tgl@sss.pgh.pa.us 2455 : 399506 : snapshot->curcid = GetCurrentCommandId(false);
2456 : :
2457 : : /*
2458 : : * This is a new snapshot, so set both refcounts are zero, and mark it as
2459 : : * not copied in persistent memory.
2460 : : */
6516 alvherre@alvh.no-ip. 2461 : 399506 : snapshot->active_count = 0;
2462 : 399506 : snapshot->regd_count = 0;
2463 : 399506 : snapshot->copied = false;
2464 : :
7605 tgl@sss.pgh.pa.us 2465 : 399506 : return snapshot;
2466 : : }
2467 : :
2468 : : /*
2469 : : * ProcArrayInstallImportedXmin -- install imported xmin into MyProc->xmin
2470 : : *
2471 : : * This is called when installing a snapshot imported from another
2472 : : * transaction. To ensure that OldestXmin doesn't go backwards, we must
2473 : : * check that the source transaction is still running, and we'd better do
2474 : : * that atomically with installing the new xmin.
2475 : : *
2476 : : * Returns true if successful, false if source xact is no longer running.
2477 : : */
2478 : : bool
3196 andres@anarazel.de 2479 : 18 : ProcArrayInstallImportedXmin(TransactionId xmin,
2480 : : VirtualTransactionId *sourcevxid)
2481 : : {
5258 tgl@sss.pgh.pa.us 2482 : 18 : bool result = false;
2483 : 18 : ProcArrayStruct *arrayP = procArray;
2484 : : int index;
2485 : :
2486 [ - + ]: 18 : Assert(TransactionIdIsNormal(xmin));
3196 andres@anarazel.de 2487 [ - + ]: 18 : if (!sourcevxid)
5258 tgl@sss.pgh.pa.us 2488 :UBC 0 : return false;
2489 : :
2490 : : /* Get lock so source xact can't end while we're doing this */
5258 tgl@sss.pgh.pa.us 2491 :CBC 18 : LWLockAcquire(ProcArrayLock, LW_SHARED);
2492 : :
2493 : : /*
2494 : : * Find the PGPROC entry of the source transaction. (This could use
2495 : : * GetPGProcByNumber(), unless it's a prepared xact. But this isn't
2496 : : * performance critical.)
2497 : : */
2498 [ + - ]: 18 : for (index = 0; index < arrayP->numProcs; index++)
2499 : : {
5026 bruce@momjian.us 2500 : 18 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 2501 : 18 : PGPROC *proc = &allProcs[pgprocno];
1945 alvherre@alvh.no-ip. 2502 : 18 : int statusFlags = ProcGlobal->statusFlags[index];
2503 : : TransactionId xid;
2504 : :
2505 : : /* Ignore procs running LAZY VACUUM */
2506 [ - + ]: 18 : if (statusFlags & PROC_IN_VACUUM)
5258 tgl@sss.pgh.pa.us 2507 :UBC 0 : continue;
2508 : :
2509 : : /* We are only interested in the specific virtual transaction. */
742 heikki.linnakangas@i 2510 [ - + ]:CBC 18 : if (proc->vxid.procNumber != sourcevxid->procNumber)
3196 andres@anarazel.de 2511 :LBC (2) : continue;
742 heikki.linnakangas@i 2512 [ - + ]:CBC 18 : if (proc->vxid.lxid != sourcevxid->localTransactionId)
5258 tgl@sss.pgh.pa.us 2513 :UBC 0 : continue;
2514 : :
2515 : : /*
2516 : : * We check the transaction's database ID for paranoia's sake: if it's
2517 : : * in another DB then its xmin does not cover us. Caller should have
2518 : : * detected this already, so we just treat any funny cases as
2519 : : * "transaction not found".
2520 : : */
5258 tgl@sss.pgh.pa.us 2521 [ - + ]:CBC 18 : if (proc->databaseId != MyDatabaseId)
5258 tgl@sss.pgh.pa.us 2522 :UBC 0 : continue;
2523 : :
2524 : : /*
2525 : : * Likewise, let's just make real sure its xmin does cover us.
2526 : : */
2040 andres@anarazel.de 2527 :CBC 18 : xid = UINT32_ACCESS_ONCE(proc->xmin);
5258 tgl@sss.pgh.pa.us 2528 [ + - ]: 18 : if (!TransactionIdIsNormal(xid) ||
2529 [ - + ]: 18 : !TransactionIdPrecedesOrEquals(xid, xmin))
5258 tgl@sss.pgh.pa.us 2530 :UBC 0 : continue;
2531 : :
2532 : : /*
2533 : : * We're good. Install the new xmin. As in GetSnapshotData, set
2534 : : * TransactionXmin too. (Note that because snapmgr.c called
2535 : : * GetSnapshotData first, we'll be overwriting a valid xmin here, so
2536 : : * we don't check that.)
2537 : : */
2040 andres@anarazel.de 2538 :CBC 18 : MyProc->xmin = TransactionXmin = xmin;
2539 : :
5258 tgl@sss.pgh.pa.us 2540 : 18 : result = true;
2541 : 18 : break;
2542 : : }
2543 : :
2544 : 18 : LWLockRelease(ProcArrayLock);
2545 : :
2546 : 18 : return result;
2547 : : }
2548 : :
2549 : : /*
2550 : : * ProcArrayInstallRestoredXmin -- install restored xmin into MyProc->xmin
2551 : : *
2552 : : * This is like ProcArrayInstallImportedXmin, but we have a pointer to the
2553 : : * PGPROC of the transaction from which we imported the snapshot, rather than
2554 : : * an XID.
2555 : : *
2556 : : * Note that this function also copies statusFlags from the source `proc` in
2557 : : * order to avoid the case where MyProc's xmin needs to be skipped for
2558 : : * computing xid horizon.
2559 : : *
2560 : : * Returns true if successful, false if source xact is no longer running.
2561 : : */
2562 : : bool
3972 rhaas@postgresql.org 2563 : 1698 : ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
2564 : : {
2565 : 1698 : bool result = false;
2566 : : TransactionId xid;
2567 : :
2568 [ - + ]: 1698 : Assert(TransactionIdIsNormal(xmin));
2569 [ - + ]: 1698 : Assert(proc != NULL);
2570 : :
2571 : : /*
2572 : : * Get an exclusive lock so that we can copy statusFlags from source proc.
2573 : : */
1577 akapila@postgresql.o 2574 : 1698 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
2575 : :
2576 : : /*
2577 : : * Be certain that the referenced PGPROC has an advertised xmin which is
2578 : : * no later than the one we're installing, so that the system-wide xmin
2579 : : * can't go backwards. Also, make sure it's running in the same database,
2580 : : * so that the per-database xmin cannot go backwards.
2581 : : */
2040 andres@anarazel.de 2582 : 1698 : xid = UINT32_ACCESS_ONCE(proc->xmin);
3972 rhaas@postgresql.org 2583 [ + - + - ]: 1698 : if (proc->databaseId == MyDatabaseId &&
2584 [ + - ]: 1698 : TransactionIdIsNormal(xid) &&
2585 : 1698 : TransactionIdPrecedesOrEquals(xid, xmin))
2586 : : {
2587 : : /*
2588 : : * Install xmin and propagate the statusFlags that affect how the
2589 : : * value is interpreted by vacuum.
2590 : : */
2040 andres@anarazel.de 2591 : 1698 : MyProc->xmin = TransactionXmin = xmin;
1396 alvherre@alvh.no-ip. 2592 : 1698 : MyProc->statusFlags = (MyProc->statusFlags & ~PROC_XMIN_FLAGS) |
2593 : 1698 : (proc->statusFlags & PROC_XMIN_FLAGS);
2594 : 1698 : ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
2595 : :
3972 rhaas@postgresql.org 2596 : 1698 : result = true;
2597 : : }
2598 : :
2599 : 1698 : LWLockRelease(ProcArrayLock);
2600 : :
2601 : 1698 : return result;
2602 : : }
2603 : :
2604 : : /*
2605 : : * GetRunningTransactionData -- returns information about running transactions.
2606 : : *
2607 : : * Similar to GetSnapshotData but returns more information. We include
2608 : : * all PGPROCs with an assigned TransactionId, even VACUUM processes and
2609 : : * prepared transactions.
2610 : : *
2611 : : * We acquire XidGenLock and ProcArrayLock, but the caller is responsible for
2612 : : * releasing them. Acquiring XidGenLock ensures that no new XIDs enter the proc
2613 : : * array until the caller has WAL-logged this snapshot, and releases the
2614 : : * lock. Acquiring ProcArrayLock ensures that no transactions commit until the
2615 : : * lock is released.
2616 : : *
2617 : : * The returned data structure is statically allocated; caller should not
2618 : : * modify it, and must not assume it is valid past the next call.
2619 : : *
2620 : : * This is never executed during recovery so there is no need to look at
2621 : : * KnownAssignedXids.
2622 : : *
2623 : : * Dummy PGPROCs from prepared transaction are included, meaning that this
2624 : : * may return entries with duplicated TransactionId values coming from
2625 : : * transaction finishing to prepare. Nothing is done about duplicated
2626 : : * entries here to not hold on ProcArrayLock more than necessary.
2627 : : *
2628 : : * We don't worry about updating other counters, we want to keep this as
2629 : : * simple as possible and leave GetSnapshotData() as the primary code for
2630 : : * that bookkeeping.
2631 : : *
2632 : : * Note that if any transaction has overflowed its cached subtransactions
2633 : : * then there is no real need include any subtransactions.
2634 : : */
2635 : : RunningTransactions
5930 simon@2ndQuadrant.co 2636 : 1479 : GetRunningTransactionData(void)
2637 : : {
2638 : : /* result workspace */
2639 : : static RunningTransactionsData CurrentRunningXactsData;
2640 : :
2641 : 1479 : ProcArrayStruct *arrayP = procArray;
2039 andres@anarazel.de 2642 : 1479 : TransactionId *other_xids = ProcGlobal->xids;
5800 tgl@sss.pgh.pa.us 2643 : 1479 : RunningTransactions CurrentRunningXacts = &CurrentRunningXactsData;
2644 : : TransactionId latestCompletedXid;
2645 : : TransactionId oldestRunningXid;
2646 : : TransactionId oldestDatabaseRunningXid;
2647 : : TransactionId *xids;
2648 : : int index;
2649 : : int count;
2650 : : int subcount;
2651 : : bool suboverflowed;
2652 : :
5930 simon@2ndQuadrant.co 2653 [ - + ]: 1479 : Assert(!RecoveryInProgress());
2654 : :
2655 : : /*
2656 : : * Allocating space for maxProcs xids is usually overkill; numProcs would
2657 : : * be sufficient. But it seems better to do the malloc while not holding
2658 : : * the lock, so we can't look at numProcs. Likewise, we allocate much
2659 : : * more subxip storage than is probably needed.
2660 : : *
2661 : : * Should only be allocated in bgwriter, since only ever executed during
2662 : : * checkpoints.
2663 : : */
2664 [ + + ]: 1479 : if (CurrentRunningXacts->xids == NULL)
2665 : : {
2666 : : /*
2667 : : * First call
2668 : : */
2669 : 581 : CurrentRunningXacts->xids = (TransactionId *)
2670 : 581 : malloc(TOTAL_MAX_CACHED_SUBXIDS * sizeof(TransactionId));
2671 [ - + ]: 581 : if (CurrentRunningXacts->xids == NULL)
5930 simon@2ndQuadrant.co 2672 [ # # ]:UBC 0 : ereport(ERROR,
2673 : : (errcode(ERRCODE_OUT_OF_MEMORY),
2674 : : errmsg("out of memory")));
2675 : : }
2676 : :
5930 simon@2ndQuadrant.co 2677 :CBC 1479 : xids = CurrentRunningXacts->xids;
2678 : :
2679 : 1479 : count = subcount = 0;
2680 : 1479 : suboverflowed = false;
2681 : :
2682 : : /*
2683 : : * Ensure that no xids enter or leave the procarray while we obtain
2684 : : * snapshot.
2685 : : */
2686 : 1479 : LWLockAcquire(ProcArrayLock, LW_SHARED);
2687 : 1479 : LWLockAcquire(XidGenLock, LW_SHARED);
2688 : :
2042 andres@anarazel.de 2689 : 1479 : latestCompletedXid =
828 heikki.linnakangas@i 2690 : 1479 : XidFromFullTransactionId(TransamVariables->latestCompletedXid);
731 akorotkov@postgresql 2691 : 1479 : oldestDatabaseRunningXid = oldestRunningXid =
828 heikki.linnakangas@i 2692 : 1479 : XidFromFullTransactionId(TransamVariables->nextXid);
2693 : :
2694 : : /*
2695 : : * Spin over procArray collecting all xids
2696 : : */
5930 simon@2ndQuadrant.co 2697 [ + + ]: 7320 : for (index = 0; index < arrayP->numProcs; index++)
2698 : : {
2699 : : TransactionId xid;
2700 : :
2701 : : /* Fetch xid just once - see GetNewTransactionId */
2039 andres@anarazel.de 2702 : 5841 : xid = UINT32_ACCESS_ONCE(other_xids[index]);
2703 : :
2704 : : /*
2705 : : * We don't need to store transactions that don't have a TransactionId
2706 : : * yet because they will not show as running on a standby server.
2707 : : */
5930 simon@2ndQuadrant.co 2708 [ + + ]: 5841 : if (!TransactionIdIsValid(xid))
2709 : 4837 : continue;
2710 : :
2711 : : /*
2712 : : * Be careful not to exclude any xids before calculating the values of
2713 : : * oldestRunningXid and suboverflowed, since these are used to clean
2714 : : * up transaction information held on standbys.
2715 : : */
2716 [ + + ]: 1004 : if (TransactionIdPrecedes(xid, oldestRunningXid))
2717 : 622 : oldestRunningXid = xid;
2718 : :
2719 : : /*
2720 : : * Also, update the oldest running xid within the current database. As
2721 : : * fetching pgprocno and PGPROC could cause cache misses, we do cheap
2722 : : * TransactionId comparison first.
2723 : : */
619 akorotkov@postgresql 2724 [ + - ]: 1004 : if (TransactionIdPrecedes(xid, oldestDatabaseRunningXid))
2725 : : {
2726 : 1004 : int pgprocno = arrayP->pgprocnos[index];
2727 : 1004 : PGPROC *proc = &allProcs[pgprocno];
2728 : :
2729 [ + + ]: 1004 : if (proc->databaseId == MyDatabaseId)
2730 : 213 : oldestDatabaseRunningXid = xid;
2731 : : }
2732 : :
2039 andres@anarazel.de 2733 [ + + ]: 1004 : if (ProcGlobal->subxidStates[index].overflowed)
4851 simon@2ndQuadrant.co 2734 : 2 : suboverflowed = true;
2735 : :
2736 : : /*
2737 : : * If we wished to exclude xids this would be the right place for it.
2738 : : * Procs with the PROC_IN_VACUUM flag set don't usually assign xids,
2739 : : * but they do during truncation at the end when they get the lock and
2740 : : * truncate, so it is not much of a problem to include them if they
2741 : : * are seen and it is cleaner to include them.
2742 : : */
2743 : :
2831 2744 : 1004 : xids[count++] = xid;
2745 : : }
2746 : :
2747 : : /*
2748 : : * Spin over procArray collecting all subxids, but only if there hasn't
2749 : : * been a suboverflow.
2750 : : */
4851 2751 [ + + ]: 1479 : if (!suboverflowed)
2752 : : {
2039 andres@anarazel.de 2753 : 1477 : XidCacheStatus *other_subxidstates = ProcGlobal->subxidStates;
2754 : :
4851 simon@2ndQuadrant.co 2755 [ + + ]: 7314 : for (index = 0; index < arrayP->numProcs; index++)
2756 : : {
2757 : 5837 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 2758 : 5837 : PGPROC *proc = &allProcs[pgprocno];
2759 : : int nsubxids;
2760 : :
2761 : : /*
2762 : : * Save subtransaction XIDs. Other backends can't add or remove
2763 : : * entries while we're holding XidGenLock.
2764 : : */
2039 2765 : 5837 : nsubxids = other_subxidstates[index].count;
2766 [ + + ]: 5837 : if (nsubxids > 0)
2767 : : {
2768 : : /* barrier not really required, as XidGenLock is held, but ... */
2683 2769 : 23 : pg_read_barrier(); /* pairs with GetNewTransactionId */
2770 : :
1132 peter@eisentraut.org 2771 : 23 : memcpy(&xids[count], proc->subxids.xids,
2772 : : nsubxids * sizeof(TransactionId));
2039 andres@anarazel.de 2773 : 23 : count += nsubxids;
2774 : 23 : subcount += nsubxids;
2775 : :
2776 : : /*
2777 : : * Top-level XID of a transaction is always less than any of
2778 : : * its subxids, so we don't need to check if any of the
2779 : : * subxids are smaller than oldestRunningXid
2780 : : */
2781 : : }
2782 : : }
2783 : : }
2784 : :
2785 : : /*
2786 : : * It's important *not* to include the limits set by slots here because
2787 : : * snapbuild.c uses oldestRunningXid to manage its xmin horizon. If those
2788 : : * were to be included here the initial value could never increase because
2789 : : * of a circular dependency where slots only increase their limits when
2790 : : * running xacts increases oldestRunningXid and running xacts only
2791 : : * increases if slots do.
2792 : : */
2793 : :
4851 simon@2ndQuadrant.co 2794 : 1479 : CurrentRunningXacts->xcnt = count - subcount;
2795 : 1479 : CurrentRunningXacts->subxcnt = subcount;
626 heikki.linnakangas@i 2796 [ + + ]: 1479 : CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY;
828 2797 : 1479 : CurrentRunningXacts->nextXid = XidFromFullTransactionId(TransamVariables->nextXid);
5930 simon@2ndQuadrant.co 2798 : 1479 : CurrentRunningXacts->oldestRunningXid = oldestRunningXid;
731 akorotkov@postgresql 2799 : 1479 : CurrentRunningXacts->oldestDatabaseRunningXid = oldestDatabaseRunningXid;
5785 simon@2ndQuadrant.co 2800 : 1479 : CurrentRunningXacts->latestCompletedXid = latestCompletedXid;
2801 : :
5784 2802 [ - + ]: 1479 : Assert(TransactionIdIsValid(CurrentRunningXacts->nextXid));
2803 [ - + ]: 1479 : Assert(TransactionIdIsValid(CurrentRunningXacts->oldestRunningXid));
2804 [ - + ]: 1479 : Assert(TransactionIdIsNormal(CurrentRunningXacts->latestCompletedXid));
2805 : :
2806 : : /* We don't release the locks here, the caller is responsible for that */
2807 : :
5930 2808 : 1479 : return CurrentRunningXacts;
2809 : : }
2810 : :
2811 : : /*
2812 : : * GetOldestActiveTransactionId()
2813 : : *
2814 : : * Similar to GetSnapshotData but returns just oldestActiveXid. We include
2815 : : * all PGPROCs with an assigned TransactionId, even VACUUM processes.
2816 : : *
2817 : : * If allDbs is true, we look at all databases, though there is no need to
2818 : : * include WALSender since this has no effect on hot standby conflicts. If
2819 : : * allDbs is false, skip processes attached to other databases.
2820 : : *
2821 : : * This is never executed during recovery so there is no need to look at
2822 : : * KnownAssignedXids.
2823 : : *
2824 : : * We don't worry about updating other counters, we want to keep this as
2825 : : * simple as possible and leave GetSnapshotData() as the primary code for
2826 : : * that bookkeeping.
2827 : : *
2828 : : * inCommitOnly indicates getting the oldestActiveXid among the transactions
2829 : : * in the commit critical section.
2830 : : */
2831 : : TransactionId
235 akapila@postgresql.o 2832 :GNC 3777 : GetOldestActiveTransactionId(bool inCommitOnly, bool allDbs)
2833 : : {
5247 simon@2ndQuadrant.co 2834 :CBC 3777 : ProcArrayStruct *arrayP = procArray;
2039 andres@anarazel.de 2835 : 3777 : TransactionId *other_xids = ProcGlobal->xids;
2836 : : TransactionId oldestRunningXid;
2837 : : int index;
2838 : :
5247 simon@2ndQuadrant.co 2839 [ - + ]: 3777 : Assert(!RecoveryInProgress());
2840 : :
2841 : : /*
2842 : : * Read nextXid, as the upper bound of what's still active.
2843 : : *
2844 : : * Reading a TransactionId is atomic, but we must grab the lock to make
2845 : : * sure that all XIDs < nextXid are already present in the proc array (or
2846 : : * have already completed), when we spin over it.
2847 : : */
3167 heikki.linnakangas@i 2848 : 3777 : LWLockAcquire(XidGenLock, LW_SHARED);
828 2849 : 3777 : oldestRunningXid = XidFromFullTransactionId(TransamVariables->nextXid);
3167 2850 : 3777 : LWLockRelease(XidGenLock);
2851 : :
2852 : : /*
2853 : : * Spin over procArray collecting all xids and subxids.
2854 : : */
2855 : 3777 : LWLockAcquire(ProcArrayLock, LW_SHARED);
5247 simon@2ndQuadrant.co 2856 [ + + ]: 21105 : for (index = 0; index < arrayP->numProcs; index++)
2857 : : {
2858 : : TransactionId xid;
235 akapila@postgresql.o 2859 :GNC 17328 : int pgprocno = arrayP->pgprocnos[index];
2860 : 17328 : PGPROC *proc = &allProcs[pgprocno];
2861 : :
2862 : : /* Fetch xid just once - see GetNewTransactionId */
2039 andres@anarazel.de 2863 :CBC 17328 : xid = UINT32_ACCESS_ONCE(other_xids[index]);
2864 : :
5247 simon@2ndQuadrant.co 2865 [ + + ]: 17328 : if (!TransactionIdIsNormal(xid))
2866 : 13775 : continue;
2867 : :
235 akapila@postgresql.o 2868 [ + + ]:GNC 3553 : if (inCommitOnly &&
2869 [ + + ]: 2656 : (proc->delayChkptFlags & DELAY_CHKPT_IN_COMMIT) == 0)
2870 : 2550 : continue;
2871 : :
2872 [ + + - + ]: 1003 : if (!allDbs && proc->databaseId != MyDatabaseId)
235 akapila@postgresql.o 2873 :UNC 0 : continue;
2874 : :
5247 simon@2ndQuadrant.co 2875 [ + + ]:CBC 1003 : if (TransactionIdPrecedes(xid, oldestRunningXid))
2876 : 669 : oldestRunningXid = xid;
2877 : :
2878 : : /*
2879 : : * Top-level XID of a transaction is always less than any of its
2880 : : * subxids, so we don't need to check if any of the subxids are
2881 : : * smaller than oldestRunningXid
2882 : : */
2883 : : }
2884 : 3777 : LWLockRelease(ProcArrayLock);
2885 : :
2886 : 3777 : return oldestRunningXid;
2887 : : }
2888 : :
2889 : : /*
2890 : : * GetOldestSafeDecodingTransactionId -- lowest xid not affected by vacuum
2891 : : *
2892 : : * Returns the oldest xid that we can guarantee not to have been affected by
2893 : : * vacuum, i.e. no rows >= that xid have been vacuumed away unless the
2894 : : * transaction aborted. Note that the value can (and most of the time will) be
2895 : : * much more conservative than what really has been affected by vacuum, but we
2896 : : * currently don't have better data available.
2897 : : *
2898 : : * This is useful to initialize the cutoff xid after which a new changeset
2899 : : * extraction replication slot can start decoding changes.
2900 : : *
2901 : : * Must be called with ProcArrayLock held either shared or exclusively,
2902 : : * although most callers will want to use exclusive mode since it is expected
2903 : : * that the caller will immediately use the xid to peg the xmin horizon.
2904 : : */
2905 : : TransactionId
3248 andres@anarazel.de 2906 : 709 : GetOldestSafeDecodingTransactionId(bool catalogOnly)
2907 : : {
4395 rhaas@postgresql.org 2908 : 709 : ProcArrayStruct *arrayP = procArray;
2909 : : TransactionId oldestSafeXid;
2910 : : int index;
2911 : 709 : bool recovery_in_progress = RecoveryInProgress();
2912 : :
2913 [ - + ]: 709 : Assert(LWLockHeldByMe(ProcArrayLock));
2914 : :
2915 : : /*
2916 : : * Acquire XidGenLock, so no transactions can acquire an xid while we're
2917 : : * running. If no transaction with xid were running concurrently a new xid
2918 : : * could influence the RecentXmin et al.
2919 : : *
2920 : : * We initialize the computation to nextXid since that's guaranteed to be
2921 : : * a safe, albeit pessimal, value.
2922 : : */
2923 : 709 : LWLockAcquire(XidGenLock, LW_SHARED);
828 heikki.linnakangas@i 2924 : 709 : oldestSafeXid = XidFromFullTransactionId(TransamVariables->nextXid);
2925 : :
2926 : : /*
2927 : : * If there's already a slot pegging the xmin horizon, we can start with
2928 : : * that value, it's guaranteed to be safe since it's computed by this
2929 : : * routine initially and has been enforced since. We can always use the
2930 : : * slot's general xmin horizon, but the catalog horizon is only usable
2931 : : * when only catalog data is going to be looked at.
2932 : : */
3248 andres@anarazel.de 2933 [ + + + + ]: 933 : if (TransactionIdIsValid(procArray->replication_slot_xmin) &&
2934 : 224 : TransactionIdPrecedes(procArray->replication_slot_xmin,
2935 : : oldestSafeXid))
2936 : 12 : oldestSafeXid = procArray->replication_slot_xmin;
2937 : :
2938 [ + + ]: 709 : if (catalogOnly &&
2939 [ + + + + ]: 366 : TransactionIdIsValid(procArray->replication_slot_catalog_xmin) &&
4395 rhaas@postgresql.org 2940 : 77 : TransactionIdPrecedes(procArray->replication_slot_catalog_xmin,
2941 : : oldestSafeXid))
2942 : 24 : oldestSafeXid = procArray->replication_slot_catalog_xmin;
2943 : :
2944 : : /*
2945 : : * If we're not in recovery, we walk over the procarray and collect the
2946 : : * lowest xid. Since we're called with ProcArrayLock held and have
2947 : : * acquired XidGenLock, no entries can vanish concurrently, since
2948 : : * ProcGlobal->xids[i] is only set with XidGenLock held and only cleared
2949 : : * with ProcArrayLock held.
2950 : : *
2951 : : * In recovery we can't lower the safe value besides what we've computed
2952 : : * above, so we'll have to wait a bit longer there. We unfortunately can
2953 : : * *not* use KnownAssignedXidsGetOldestXmin() since the KnownAssignedXids
2954 : : * machinery can miss values and return an older value than is safe.
2955 : : */
2956 [ + + ]: 709 : if (!recovery_in_progress)
2957 : : {
2039 andres@anarazel.de 2958 : 676 : TransactionId *other_xids = ProcGlobal->xids;
2959 : :
2960 : : /*
2961 : : * Spin over procArray collecting min(ProcGlobal->xids[i])
2962 : : */
4395 rhaas@postgresql.org 2963 [ + + ]: 3470 : for (index = 0; index < arrayP->numProcs; index++)
2964 : : {
2965 : : TransactionId xid;
2966 : :
2967 : : /* Fetch xid just once - see GetNewTransactionId */
2039 andres@anarazel.de 2968 : 2794 : xid = UINT32_ACCESS_ONCE(other_xids[index]);
2969 : :
4395 rhaas@postgresql.org 2970 [ + + ]: 2794 : if (!TransactionIdIsNormal(xid))
2971 : 2784 : continue;
2972 : :
2973 [ + + ]: 10 : if (TransactionIdPrecedes(xid, oldestSafeXid))
2974 : 8 : oldestSafeXid = xid;
2975 : : }
2976 : : }
2977 : :
2978 : 709 : LWLockRelease(XidGenLock);
2979 : :
2980 : 709 : return oldestSafeXid;
2981 : : }
2982 : :
2983 : : /*
2984 : : * GetVirtualXIDsDelayingChkpt -- Get the VXIDs of transactions that are
2985 : : * delaying checkpoint because they have critical actions in progress.
2986 : : *
2987 : : * Constructs an array of VXIDs of transactions that are currently in commit
2988 : : * critical sections, as shown by having specified delayChkptFlags bits set
2989 : : * in their PGPROC.
2990 : : *
2991 : : * Returns a palloc'd array that should be freed by the caller.
2992 : : * *nvxids is the number of valid entries.
2993 : : *
2994 : : * Note that because backends set or clear delayChkptFlags without holding any
2995 : : * lock, the result is somewhat indeterminate, but we don't really care. Even
2996 : : * in a multiprocessor with delayed writes to shared memory, it should be
2997 : : * certain that setting of delayChkptFlags will propagate to shared memory
2998 : : * when the backend takes a lock, so we cannot fail to see a virtual xact as
2999 : : * delayChkptFlags if it's already inserted its commit record. Whether it
3000 : : * takes a little while for clearing of delayChkptFlags to propagate is
3001 : : * unimportant for correctness.
3002 : : */
3003 : : VirtualTransactionId *
1452 3004 : 3196 : GetVirtualXIDsDelayingChkpt(int *nvxids, int type)
3005 : : {
3006 : : VirtualTransactionId *vxids;
6921 tgl@sss.pgh.pa.us 3007 : 3196 : ProcArrayStruct *arrayP = procArray;
4850 simon@2ndQuadrant.co 3008 : 3196 : int count = 0;
3009 : : int index;
3010 : :
1452 rhaas@postgresql.org 3011 [ - + ]: 3196 : Assert(type != 0);
3012 : :
3013 : : /* allocate what's certainly enough result space */
95 michael@paquier.xyz 3014 :GNC 3196 : vxids = palloc_array(VirtualTransactionId, arrayP->maxProcs);
3015 : :
6921 tgl@sss.pgh.pa.us 3016 :CBC 3196 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3017 : :
3018 [ + + ]: 10520 : for (index = 0; index < arrayP->numProcs; index++)
3019 : : {
4673 bruce@momjian.us 3020 : 7324 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3021 : 7324 : PGPROC *proc = &allProcs[pgprocno];
3022 : :
1437 rhaas@postgresql.org 3023 [ + + ]: 7324 : if ((proc->delayChkptFlags & type) != 0)
3024 : : {
3025 : : VirtualTransactionId vxid;
3026 : :
4850 simon@2ndQuadrant.co 3027 : 25 : GET_VXID_FROM_PGPROC(vxid, *proc);
3028 [ + - ]: 25 : if (VirtualTransactionIdIsValid(vxid))
3029 : 25 : vxids[count++] = vxid;
3030 : : }
3031 : : }
3032 : :
6921 tgl@sss.pgh.pa.us 3033 : 3196 : LWLockRelease(ProcArrayLock);
3034 : :
4850 simon@2ndQuadrant.co 3035 : 3196 : *nvxids = count;
3036 : 3196 : return vxids;
3037 : : }
3038 : :
3039 : : /*
3040 : : * HaveVirtualXIDsDelayingChkpt -- Are any of the specified VXIDs delaying?
3041 : : *
3042 : : * This is used with the results of GetVirtualXIDsDelayingChkpt to see if any
3043 : : * of the specified VXIDs are still in critical sections of code.
3044 : : *
3045 : : * Note: this is O(N^2) in the number of vxacts that are/were delaying, but
3046 : : * those numbers should be small enough for it not to be a problem.
3047 : : */
3048 : : bool
1452 rhaas@postgresql.org 3049 : 18 : HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids, int type)
3050 : : {
6695 bruce@momjian.us 3051 : 18 : bool result = false;
6921 tgl@sss.pgh.pa.us 3052 : 18 : ProcArrayStruct *arrayP = procArray;
3053 : : int index;
3054 : :
1452 rhaas@postgresql.org 3055 [ - + ]: 18 : Assert(type != 0);
3056 : :
6921 tgl@sss.pgh.pa.us 3057 : 18 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3058 : :
4659 noah@leadboat.com 3059 [ + + ]: 208 : for (index = 0; index < arrayP->numProcs; index++)
3060 : : {
3061 : 190 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3062 : 190 : PGPROC *proc = &allProcs[pgprocno];
3063 : : VirtualTransactionId vxid;
3064 : :
4659 noah@leadboat.com 3065 : 190 : GET_VXID_FROM_PGPROC(vxid, *proc);
3066 : :
1437 rhaas@postgresql.org 3067 [ + + ]: 190 : if ((proc->delayChkptFlags & type) != 0 &&
1452 3068 [ + - ]: 4 : VirtualTransactionIdIsValid(vxid))
3069 : : {
3070 : : int i;
3071 : :
4659 noah@leadboat.com 3072 [ + + ]: 13 : for (i = 0; i < nvxids; i++)
3073 : : {
3074 [ - + - - ]: 9 : if (VirtualTransactionIdEquals(vxid, vxids[i]))
3075 : : {
6921 tgl@sss.pgh.pa.us 3076 :LBC (2) : result = true;
3077 : (2) : break;
3078 : : }
3079 : : }
4659 noah@leadboat.com 3080 [ - + ]:CBC 4 : if (result)
4659 noah@leadboat.com 3081 :LBC (2) : break;
3082 : : }
3083 : : }
3084 : :
6921 tgl@sss.pgh.pa.us 3085 :CBC 18 : LWLockRelease(ProcArrayLock);
3086 : :
3087 : 18 : return result;
3088 : : }
3089 : :
3090 : : /*
3091 : : * ProcNumberGetProc -- get a backend's PGPROC given its proc number
3092 : : *
3093 : : * The result may be out of date arbitrarily quickly, so the caller
3094 : : * must be careful about how this information is used. NULL is
3095 : : * returned if the backend is not active.
3096 : : */
3097 : : PGPROC *
742 heikki.linnakangas@i 3098 : 539 : ProcNumberGetProc(ProcNumber procNumber)
3099 : : {
3100 : : PGPROC *result;
3101 : :
3102 [ + + - + ]: 539 : if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
3103 : 1 : return NULL;
3104 : 538 : result = GetPGProcByNumber(procNumber);
3105 : :
3106 [ + + ]: 538 : if (result->pid == 0)
3107 : 3 : return NULL;
3108 : :
3109 : 535 : return result;
3110 : : }
3111 : :
3112 : : /*
3113 : : * ProcNumberGetTransactionIds -- get a backend's transaction status
3114 : : *
3115 : : * Get the xid, xmin, nsubxid and overflow status of the backend. The
3116 : : * result may be out of date arbitrarily quickly, so the caller must be
3117 : : * careful about how this information is used.
3118 : : */
3119 : : void
3120 : 12057 : ProcNumberGetTransactionIds(ProcNumber procNumber, TransactionId *xid,
3121 : : TransactionId *xmin, int *nsubxid, bool *overflowed)
3122 : : {
3123 : : PGPROC *proc;
3124 : :
3125 : 12057 : *xid = InvalidTransactionId;
3126 : 12057 : *xmin = InvalidTransactionId;
3127 : 12057 : *nsubxid = 0;
3128 : 12057 : *overflowed = false;
3129 : :
3130 [ + - - + ]: 12057 : if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
742 heikki.linnakangas@i 3131 :UBC 0 : return;
742 heikki.linnakangas@i 3132 :CBC 12057 : proc = GetPGProcByNumber(procNumber);
3133 : :
3134 : : /* Need to lock out additions/removals of backends */
3135 : 12057 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3136 : :
3137 [ + - ]: 12057 : if (proc->pid != 0)
3138 : : {
3139 : 12057 : *xid = proc->xid;
3140 : 12057 : *xmin = proc->xmin;
3141 : 12057 : *nsubxid = proc->subxidStatus.count;
3142 : 12057 : *overflowed = proc->subxidStatus.overflowed;
3143 : : }
3144 : :
3145 : 12057 : LWLockRelease(ProcArrayLock);
3146 : : }
3147 : :
3148 : : /*
3149 : : * BackendPidGetProc -- get a backend's PGPROC given its PID
3150 : : *
3151 : : * Returns NULL if not found. Note that it is up to the caller to be
3152 : : * sure that the question remains meaningful for long enough for the
3153 : : * answer to be used ...
3154 : : */
3155 : : PGPROC *
7605 tgl@sss.pgh.pa.us 3156 : 12523 : BackendPidGetProc(int pid)
3157 : : {
3158 : : PGPROC *result;
3159 : :
3674 3160 [ + + ]: 12523 : if (pid == 0) /* never match dummy PGPROCs */
3161 : 3 : return NULL;
3162 : :
3163 : 12520 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3164 : :
3165 : 12520 : result = BackendPidGetProcWithLock(pid);
3166 : :
3167 : 12520 : LWLockRelease(ProcArrayLock);
3168 : :
3169 : 12520 : return result;
3170 : : }
3171 : :
3172 : : /*
3173 : : * BackendPidGetProcWithLock -- get a backend's PGPROC given its PID
3174 : : *
3175 : : * Same as above, except caller must be holding ProcArrayLock. The found
3176 : : * entry, if any, can be assumed to be valid as long as the lock remains held.
3177 : : */
3178 : : PGPROC *
3179 : 14515 : BackendPidGetProcWithLock(int pid)
3180 : : {
7605 3181 : 14515 : PGPROC *result = NULL;
3182 : 14515 : ProcArrayStruct *arrayP = procArray;
3183 : : int index;
3184 : :
7576 3185 [ - + ]: 14515 : if (pid == 0) /* never match dummy PGPROCs */
7576 tgl@sss.pgh.pa.us 3186 :UBC 0 : return NULL;
3187 : :
7605 tgl@sss.pgh.pa.us 3188 [ + + ]:CBC 56584 : for (index = 0; index < arrayP->numProcs; index++)
3189 : : {
5224 rhaas@postgresql.org 3190 : 50538 : PGPROC *proc = &allProcs[arrayP->pgprocnos[index]];
3191 : :
7605 tgl@sss.pgh.pa.us 3192 [ + + ]: 50538 : if (proc->pid == pid)
3193 : : {
3194 : 8469 : result = proc;
3195 : 8469 : break;
3196 : : }
3197 : : }
3198 : :
3199 : 14515 : return result;
3200 : : }
3201 : :
3202 : : /*
3203 : : * BackendXidGetPid -- get a backend's pid given its XID
3204 : : *
3205 : : * Returns 0 if not found or it's a prepared transaction. Note that
3206 : : * it is up to the caller to be sure that the question remains
3207 : : * meaningful for long enough for the answer to be used ...
3208 : : *
3209 : : * Only main transaction Ids are considered. This function is mainly
3210 : : * useful for determining what backend owns a lock.
3211 : : *
3212 : : * Beware that not every xact has an XID assigned. However, as long as you
3213 : : * only call this using an XID found on disk, you're safe.
3214 : : */
3215 : : int
7512 ishii@postgresql.org 3216 : 30 : BackendXidGetPid(TransactionId xid)
3217 : : {
7456 bruce@momjian.us 3218 : 30 : int result = 0;
7512 ishii@postgresql.org 3219 : 30 : ProcArrayStruct *arrayP = procArray;
2039 andres@anarazel.de 3220 : 30 : TransactionId *other_xids = ProcGlobal->xids;
3221 : : int index;
3222 : :
7512 ishii@postgresql.org 3223 [ - + ]: 30 : if (xid == InvalidTransactionId) /* never match invalid xid */
7512 ishii@postgresql.org 3224 :UBC 0 : return 0;
3225 : :
7512 ishii@postgresql.org 3226 :CBC 30 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3227 : :
3228 [ + + ]: 92 : for (index = 0; index < arrayP->numProcs; index++)
3229 : : {
2039 andres@anarazel.de 3230 [ + + ]: 84 : if (other_xids[index] == xid)
3231 : : {
919 michael@paquier.xyz 3232 : 22 : int pgprocno = arrayP->pgprocnos[index];
3233 : 22 : PGPROC *proc = &allProcs[pgprocno];
3234 : :
7512 ishii@postgresql.org 3235 : 22 : result = proc->pid;
3236 : 22 : break;
3237 : : }
3238 : : }
3239 : :
3240 : 30 : LWLockRelease(ProcArrayLock);
3241 : :
3242 : 30 : return result;
3243 : : }
3244 : :
3245 : : /*
3246 : : * IsBackendPid -- is a given pid a running backend
3247 : : *
3248 : : * This is not called by the backend, but is called by external modules.
3249 : : */
3250 : : bool
7605 tgl@sss.pgh.pa.us 3251 : 2 : IsBackendPid(int pid)
3252 : : {
3253 : 2 : return (BackendPidGetProc(pid) != NULL);
3254 : : }
3255 : :
3256 : :
3257 : : /*
3258 : : * GetCurrentVirtualXIDs -- returns an array of currently active VXIDs.
3259 : : *
3260 : : * The array is palloc'd. The number of valid entries is returned into *nvxids.
3261 : : *
3262 : : * The arguments allow filtering the set of VXIDs returned. Our own process
3263 : : * is always skipped. In addition:
3264 : : * If limitXmin is not InvalidTransactionId, skip processes with
3265 : : * xmin > limitXmin.
3266 : : * If excludeXmin0 is true, skip processes with xmin = 0.
3267 : : * If allDbs is false, skip processes attached to other databases.
3268 : : * If excludeVacuum isn't zero, skip processes for which
3269 : : * (statusFlags & excludeVacuum) is not zero.
3270 : : *
3271 : : * Note: the purpose of the limitXmin and excludeXmin0 parameters is to
3272 : : * allow skipping backends whose oldest live snapshot is no older than
3273 : : * some snapshot we have. Since we examine the procarray with only shared
3274 : : * lock, there are race conditions: a backend could set its xmin just after
3275 : : * we look. Indeed, on multiprocessors with weak memory ordering, the
3276 : : * other backend could have set its xmin *before* we look. We know however
3277 : : * that such a backend must have held shared ProcArrayLock overlapping our
3278 : : * own hold of ProcArrayLock, else we would see its xmin update. Therefore,
3279 : : * any snapshot the other backend is taking concurrently with our scan cannot
3280 : : * consider any transactions as still running that we think are committed
3281 : : * (since backends must hold ProcArrayLock exclusive to commit).
3282 : : */
3283 : : VirtualTransactionId *
6189 3284 : 409 : GetCurrentVirtualXIDs(TransactionId limitXmin, bool excludeXmin0,
3285 : : bool allDbs, int excludeVacuum,
3286 : : int *nvxids)
3287 : : {
3288 : : VirtualTransactionId *vxids;
6766 3289 : 409 : ProcArrayStruct *arrayP = procArray;
3290 : 409 : int count = 0;
3291 : : int index;
3292 : :
3293 : : /* allocate what's certainly enough result space */
95 michael@paquier.xyz 3294 :GNC 409 : vxids = palloc_array(VirtualTransactionId, arrayP->maxProcs);
3295 : :
6766 tgl@sss.pgh.pa.us 3296 :CBC 409 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3297 : :
3298 [ + + ]: 2416 : for (index = 0; index < arrayP->numProcs; index++)
3299 : : {
5026 bruce@momjian.us 3300 : 2007 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3301 : 2007 : PGPROC *proc = &allProcs[pgprocno];
1945 alvherre@alvh.no-ip. 3302 : 2007 : uint8 statusFlags = ProcGlobal->statusFlags[index];
3303 : :
6766 tgl@sss.pgh.pa.us 3304 [ + + ]: 2007 : if (proc == MyProc)
3305 : 409 : continue;
3306 : :
1945 alvherre@alvh.no-ip. 3307 [ + + ]: 1598 : if (excludeVacuum & statusFlags)
6640 tgl@sss.pgh.pa.us 3308 : 20 : continue;
3309 : :
6764 3310 [ + - + + ]: 1578 : if (allDbs || proc->databaseId == MyDatabaseId)
3311 : : {
3312 : : /* Fetch xmin just once - might change on us */
2040 andres@anarazel.de 3313 : 688 : TransactionId pxmin = UINT32_ACCESS_ONCE(proc->xmin);
3314 : :
6189 tgl@sss.pgh.pa.us 3315 [ + - + + ]: 688 : if (excludeXmin0 && !TransactionIdIsValid(pxmin))
3316 : 422 : continue;
3317 : :
3318 : : /*
3319 : : * InvalidTransactionId precedes all other XIDs, so a proc that
3320 : : * hasn't set xmin yet will not be rejected by this test.
3321 : : */
6764 3322 [ + - + + ]: 532 : if (!TransactionIdIsValid(limitXmin) ||
6189 3323 : 266 : TransactionIdPrecedesOrEquals(pxmin, limitXmin))
3324 : : {
3325 : : VirtualTransactionId vxid;
3326 : :
6764 3327 : 225 : GET_VXID_FROM_PGPROC(vxid, *proc);
3328 [ + - ]: 225 : if (VirtualTransactionIdIsValid(vxid))
3329 : 225 : vxids[count++] = vxid;
3330 : : }
3331 : : }
3332 : : }
3333 : :
6766 3334 : 409 : LWLockRelease(ProcArrayLock);
3335 : :
6189 3336 : 409 : *nvxids = count;
6766 3337 : 409 : return vxids;
3338 : : }
3339 : :
3340 : : /*
3341 : : * GetConflictingVirtualXIDs -- returns an array of currently active VXIDs.
3342 : : *
3343 : : * Usage is limited to conflict resolution during recovery on standby servers.
3344 : : * limitXmin is supplied as either a cutoff with snapshotConflictHorizon
3345 : : * semantics, or InvalidTransactionId in cases where caller cannot accurately
3346 : : * determine a safe snapshotConflictHorizon value.
3347 : : *
3348 : : * If limitXmin is InvalidTransactionId then we want to kill everybody,
3349 : : * so we're not worried if they have a snapshot or not, nor does it really
3350 : : * matter what type of lock we hold. Caller must avoid calling here with
3351 : : * snapshotConflictHorizon style cutoffs that were set to InvalidTransactionId
3352 : : * during original execution, since that actually indicates that there is
3353 : : * definitely no need for a recovery conflict (the snapshotConflictHorizon
3354 : : * convention for InvalidTransactionId values is the opposite of our own!).
3355 : : *
3356 : : * All callers that are checking xmins always now supply a valid and useful
3357 : : * value for limitXmin. The limitXmin is always lower than the lowest
3358 : : * numbered KnownAssignedXid that is not already a FATAL error. This is
3359 : : * because we only care about cleanup records that are cleaning up tuple
3360 : : * versions from committed transactions. In that case they will only occur
3361 : : * at the point where the record is less than the lowest running xid. That
3362 : : * allows us to say that if any backend takes a snapshot concurrently with
3363 : : * us then the conflict assessment made here would never include the snapshot
3364 : : * that is being derived. So we take LW_SHARED on the ProcArray and allow
3365 : : * concurrent snapshots when limitXmin is valid. We might think about adding
3366 : : * Assert(limitXmin < lowest(KnownAssignedXids))
3367 : : * but that would not be true in the case of FATAL errors lagging in array,
3368 : : * but we already know those are bogus anyway, so we skip that test.
3369 : : *
3370 : : * If dbOid is valid we skip backends attached to other databases.
3371 : : *
3372 : : * Be careful to *not* pfree the result from this function. We reuse
3373 : : * this array sufficiently often that we use malloc for the result.
3374 : : */
3375 : : VirtualTransactionId *
5895 simon@2ndQuadrant.co 3376 : 13382 : GetConflictingVirtualXIDs(TransactionId limitXmin, Oid dbOid)
3377 : : {
3378 : : static VirtualTransactionId *vxids;
5930 3379 : 13382 : ProcArrayStruct *arrayP = procArray;
3380 : 13382 : int count = 0;
3381 : : int index;
3382 : :
3383 : : /*
3384 : : * If first time through, get workspace to remember main XIDs in. We
3385 : : * malloc it permanently to avoid repeated palloc/pfree overhead. Allow
3386 : : * result space, remembering room for a terminator.
3387 : : */
3388 [ + + ]: 13382 : if (vxids == NULL)
3389 : : {
3390 : 19 : vxids = (VirtualTransactionId *)
3391 : 19 : malloc(sizeof(VirtualTransactionId) * (arrayP->maxProcs + 1));
3392 [ - + ]: 19 : if (vxids == NULL)
5930 simon@2ndQuadrant.co 3393 [ # # ]:UBC 0 : ereport(ERROR,
3394 : : (errcode(ERRCODE_OUT_OF_MEMORY),
3395 : : errmsg("out of memory")));
3396 : : }
3397 : :
5807 simon@2ndQuadrant.co 3398 :CBC 13382 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3399 : :
5930 3400 [ + + ]: 13530 : for (index = 0; index < arrayP->numProcs; index++)
3401 : : {
5026 bruce@momjian.us 3402 : 148 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3403 : 148 : PGPROC *proc = &allProcs[pgprocno];
3404 : :
3405 : : /* Exclude prepared transactions */
5930 simon@2ndQuadrant.co 3406 [ - + ]: 148 : if (proc->pid == 0)
5930 simon@2ndQuadrant.co 3407 :UBC 0 : continue;
3408 : :
5930 simon@2ndQuadrant.co 3409 [ + + ]:CBC 148 : if (!OidIsValid(dbOid) ||
3410 [ + + ]: 142 : proc->databaseId == dbOid)
3411 : : {
3412 : : /* Fetch xmin just once - can't change on us, but good coding */
2040 andres@anarazel.de 3413 : 17 : TransactionId pxmin = UINT32_ACCESS_ONCE(proc->xmin);
3414 : :
3415 : : /*
3416 : : * We ignore an invalid pxmin because this means that backend has
3417 : : * no snapshot currently. We hold a Share lock to avoid contention
3418 : : * with users taking snapshots. That is not a problem because the
3419 : : * current xmin is always at least one higher than the latest
3420 : : * removed xid, so any new snapshot would never conflict with the
3421 : : * test here.
3422 : : */
5807 simon@2ndQuadrant.co 3423 [ + + + + ]: 17 : if (!TransactionIdIsValid(limitXmin) ||
3424 [ + + ]: 3 : (TransactionIdIsValid(pxmin) && !TransactionIdFollows(pxmin, limitXmin)))
3425 : : {
3426 : : VirtualTransactionId vxid;
3427 : :
5930 3428 : 2 : GET_VXID_FROM_PGPROC(vxid, *proc);
3429 [ + - ]: 2 : if (VirtualTransactionIdIsValid(vxid))
3430 : 2 : vxids[count++] = vxid;
3431 : : }
3432 : : }
3433 : : }
3434 : :
3435 : 13382 : LWLockRelease(ProcArrayLock);
3436 : :
3437 : : /* add the terminator */
742 heikki.linnakangas@i 3438 : 13382 : vxids[count].procNumber = INVALID_PROC_NUMBER;
5930 simon@2ndQuadrant.co 3439 : 13382 : vxids[count].localTransactionId = InvalidLocalTransactionId;
3440 : :
3441 : 13382 : return vxids;
3442 : : }
3443 : :
3444 : : /*
3445 : : * SignalRecoveryConflict -- signal that a process is blocking recovery
3446 : : *
3447 : : * The 'pid' is redundant with 'proc', but it acts as a cross-check to
3448 : : * detect process had exited and the PGPROC entry was reused for a different
3449 : : * process.
3450 : : *
3451 : : * Returns true if the process was signaled, or false if not found.
3452 : : */
3453 : : bool
33 heikki.linnakangas@i 3454 :GNC 5 : SignalRecoveryConflict(PGPROC *proc, pid_t pid, RecoveryConflictReason reason)
3455 : : {
3456 : 5 : bool found = false;
3457 : :
3458 : 5 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3459 : :
3460 : : /*
3461 : : * Kill the pid if it's still here. If not, that's what we wanted so
3462 : : * ignore any errors.
3463 : : */
3464 [ + - ]: 5 : if (proc->pid == pid)
3465 : : {
3466 : 5 : (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
3467 : :
3468 : : /* wake up the process */
3469 : 5 : (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, GetNumberFromPGProc(proc));
3470 : 5 : found = true;
3471 : : }
3472 : :
3473 : 5 : LWLockRelease(ProcArrayLock);
3474 : :
3475 : 5 : return found;
3476 : : }
3477 : :
3478 : : /*
3479 : : * SignalRecoveryConflictWithVirtualXID -- signal that a VXID is blocking recovery
3480 : : *
3481 : : * Like SignalRecoveryConflict, but the target is identified by VXID
3482 : : */
3483 : : bool
3484 : 5 : SignalRecoveryConflictWithVirtualXID(VirtualTransactionId vxid, RecoveryConflictReason reason)
3485 : : {
5930 simon@2ndQuadrant.co 3486 :CBC 5 : ProcArrayStruct *arrayP = procArray;
3487 : : int index;
3488 : 5 : pid_t pid = 0;
3489 : :
3490 : 5 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3491 : :
3492 [ + - ]: 5 : for (index = 0; index < arrayP->numProcs; index++)
3493 : : {
5026 bruce@momjian.us 3494 : 5 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3495 : 5 : PGPROC *proc = &allProcs[pgprocno];
3496 : : VirtualTransactionId procvxid;
3497 : :
5930 simon@2ndQuadrant.co 3498 : 5 : GET_VXID_FROM_PGPROC(procvxid, *proc);
3499 : :
742 heikki.linnakangas@i 3500 [ + - ]: 5 : if (procvxid.procNumber == vxid.procNumber &&
5930 simon@2ndQuadrant.co 3501 [ + - ]: 5 : procvxid.localTransactionId == vxid.localTransactionId)
3502 : : {
3503 : 5 : pid = proc->pid;
5902 3504 [ + - ]: 5 : if (pid != 0)
3505 : : {
33 heikki.linnakangas@i 3506 :GNC 5 : (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
3507 : :
3508 : : /*
3509 : : * Kill the pid if it's still here. If not, that's what we
3510 : : * wanted so ignore any errors.
3511 : : */
3512 : 5 : (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, vxid.procNumber);
3513 : : }
5930 simon@2ndQuadrant.co 3514 :CBC 5 : break;
3515 : : }
3516 : : }
3517 : :
3518 : 5 : LWLockRelease(ProcArrayLock);
3519 : :
33 heikki.linnakangas@i 3520 :GNC 5 : return pid != 0;
3521 : : }
3522 : :
3523 : : /*
3524 : : * SignalRecoveryConflictWithDatabase -- signal backends using specified database
3525 : : *
3526 : : * Like SignalRecoveryConflict, but signals all backends using the database.
3527 : : */
3528 : : void
3529 : 10 : SignalRecoveryConflictWithDatabase(Oid databaseid, RecoveryConflictReason reason)
3530 : : {
3531 : 10 : ProcArrayStruct *arrayP = procArray;
3532 : : int index;
3533 : :
3534 : : /* tell all backends to die */
3535 : 10 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
3536 : :
3537 [ + + ]: 20 : for (index = 0; index < arrayP->numProcs; index++)
3538 : : {
3539 : 10 : int pgprocno = arrayP->pgprocnos[index];
3540 : 10 : PGPROC *proc = &allProcs[pgprocno];
3541 : :
3542 [ + + + - ]: 10 : if (databaseid == InvalidOid || proc->databaseId == databaseid)
3543 : : {
3544 : : VirtualTransactionId procvxid;
3545 : : pid_t pid;
3546 : :
3547 : 10 : GET_VXID_FROM_PGPROC(procvxid, *proc);
3548 : :
3549 : 10 : pid = proc->pid;
3550 [ + - ]: 10 : if (pid != 0)
3551 : : {
3552 : 10 : (void) pg_atomic_fetch_or_u32(&proc->pendingRecoveryConflicts, (1 << reason));
3553 : :
3554 : : /*
3555 : : * Kill the pid if it's still here. If not, that's what we
3556 : : * wanted so ignore any errors.
3557 : : */
3558 : 10 : (void) SendProcSignal(pid, PROCSIG_RECOVERY_CONFLICT, procvxid.procNumber);
3559 : : }
3560 : : }
3561 : : }
3562 : :
3563 : 10 : LWLockRelease(ProcArrayLock);
5930 simon@2ndQuadrant.co 3564 :GIC 10 : }
3565 : :
3566 : : /*
3567 : : * MinimumActiveBackends --- count backends (other than myself) that are
3568 : : * in active transactions. Return true if the count exceeds the
3569 : : * minimum threshold passed. This is used as a heuristic to decide if
3570 : : * a pre-XLOG-flush delay is worthwhile during commit.
3571 : : *
3572 : : * Do not count backends that are blocked waiting for locks, since they are
3573 : : * not going to get to run until someone else commits.
3574 : : */
3575 : : bool
5576 simon@2ndQuadrant.co 3576 :UBC 0 : MinimumActiveBackends(int min)
3577 : : {
7605 tgl@sss.pgh.pa.us 3578 : 0 : ProcArrayStruct *arrayP = procArray;
3579 : 0 : int count = 0;
3580 : : int index;
3581 : :
3582 : : /* Quick short-circuit if no minimum is specified */
5576 simon@2ndQuadrant.co 3583 [ # # ]: 0 : if (min == 0)
3584 : 0 : return true;
3585 : :
3586 : : /*
3587 : : * Note: for speed, we don't acquire ProcArrayLock. This is a little bit
3588 : : * bogus, but since we are only testing fields for zero or nonzero, it
3589 : : * should be OK. The result is only used for heuristic purposes anyway...
3590 : : */
7605 tgl@sss.pgh.pa.us 3591 [ # # ]: 0 : for (index = 0; index < arrayP->numProcs; index++)
3592 : : {
5026 bruce@momjian.us 3593 : 0 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3594 : 0 : PGPROC *proc = &allProcs[pgprocno];
3595 : :
3596 : : /*
3597 : : * Since we're not holding a lock, need to be prepared to deal with
3598 : : * garbage, as someone could have incremented numProcs but not yet
3599 : : * filled the structure.
3600 : : *
3601 : : * If someone just decremented numProcs, 'proc' could also point to a
3602 : : * PGPROC entry that's no longer in the array. It still points to a
3603 : : * PGPROC struct, though, because freed PGPROC entries just go to the
3604 : : * free list and are recycled. Its contents are nonsense in that case,
3605 : : * but that's acceptable for this function.
3606 : : */
4080 sfrost@snowman.net 3607 [ # # ]: 0 : if (pgprocno == -1)
3608 : 0 : continue; /* do not count deleted entries */
7605 tgl@sss.pgh.pa.us 3609 [ # # ]: 0 : if (proc == MyProc)
3610 : 0 : continue; /* do not count myself */
2039 andres@anarazel.de 3611 [ # # ]: 0 : if (proc->xid == InvalidTransactionId)
5224 rhaas@postgresql.org 3612 : 0 : continue; /* do not count if no XID assigned */
7576 tgl@sss.pgh.pa.us 3613 [ # # ]: 0 : if (proc->pid == 0)
3614 : 0 : continue; /* do not count prepared xacts */
7605 3615 [ # # ]: 0 : if (proc->waitLock != NULL)
3616 : 0 : continue; /* do not count if blocked on a lock */
3617 : 0 : count++;
5576 simon@2ndQuadrant.co 3618 [ # # ]: 0 : if (count >= min)
3619 : 0 : break;
3620 : : }
3621 : :
3622 : 0 : return count >= min;
3623 : : }
3624 : :
3625 : : /*
3626 : : * CountDBBackends --- count backends that are using specified database
3627 : : */
3628 : : int
7532 tgl@sss.pgh.pa.us 3629 :CBC 16 : CountDBBackends(Oid databaseid)
3630 : : {
3631 : 16 : ProcArrayStruct *arrayP = procArray;
3632 : 16 : int count = 0;
3633 : : int index;
3634 : :
3635 : 16 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3636 : :
3637 [ + + ]: 23 : for (index = 0; index < arrayP->numProcs; index++)
3638 : : {
5026 bruce@momjian.us 3639 : 7 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3640 : 7 : PGPROC *proc = &allProcs[pgprocno];
3641 : :
7532 tgl@sss.pgh.pa.us 3642 [ - + ]: 7 : if (proc->pid == 0)
7532 tgl@sss.pgh.pa.us 3643 :UBC 0 : continue; /* do not count prepared xacts */
5806 simon@2ndQuadrant.co 3644 [ + - ]:CBC 7 : if (!OidIsValid(databaseid) ||
3645 [ + + ]: 7 : proc->databaseId == databaseid)
7532 tgl@sss.pgh.pa.us 3646 : 2 : count++;
3647 : : }
3648 : :
3649 : 16 : LWLockRelease(ProcArrayLock);
3650 : :
3651 : 16 : return count;
3652 : : }
3653 : :
3654 : : /*
3655 : : * CountDBConnections --- counts database backends (only regular backends)
3656 : : */
3657 : : int
3329 andrew@dunslane.net 3658 :UBC 0 : CountDBConnections(Oid databaseid)
3659 : : {
3660 : 0 : ProcArrayStruct *arrayP = procArray;
3661 : 0 : int count = 0;
3662 : : int index;
3663 : :
3664 : 0 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3665 : :
3666 [ # # ]: 0 : for (index = 0; index < arrayP->numProcs; index++)
3667 : : {
3668 : 0 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3669 : 0 : PGPROC *proc = &allProcs[pgprocno];
3670 : :
3329 andrew@dunslane.net 3671 [ # # ]: 0 : if (proc->pid == 0)
3672 : 0 : continue; /* do not count prepared xacts */
39 heikki.linnakangas@i 3673 [ # # ]:UNC 0 : if (proc->backendType != B_BACKEND)
442 tgl@sss.pgh.pa.us 3674 :UBC 0 : continue; /* count only regular backend processes */
3329 andrew@dunslane.net 3675 [ # # ]: 0 : if (!OidIsValid(databaseid) ||
3676 [ # # ]: 0 : proc->databaseId == databaseid)
3677 : 0 : count++;
3678 : : }
3679 : :
3680 : 0 : LWLockRelease(ProcArrayLock);
3681 : :
3682 : 0 : return count;
3683 : : }
3684 : :
3685 : : /*
3686 : : * CountUserBackends --- count backends that are used by specified user
3687 : : * (only regular backends, not any type of background worker)
3688 : : */
3689 : : int
7532 tgl@sss.pgh.pa.us 3690 : 0 : CountUserBackends(Oid roleid)
3691 : : {
3692 : 0 : ProcArrayStruct *arrayP = procArray;
3693 : 0 : int count = 0;
3694 : : int index;
3695 : :
3696 : 0 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3697 : :
3698 [ # # ]: 0 : for (index = 0; index < arrayP->numProcs; index++)
3699 : : {
5026 bruce@momjian.us 3700 : 0 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3701 : 0 : PGPROC *proc = &allProcs[pgprocno];
3702 : :
7532 tgl@sss.pgh.pa.us 3703 [ # # ]: 0 : if (proc->pid == 0)
3704 : 0 : continue; /* do not count prepared xacts */
39 heikki.linnakangas@i 3705 [ # # ]:UNC 0 : if (proc->backendType != B_BACKEND)
442 tgl@sss.pgh.pa.us 3706 :UBC 0 : continue; /* count only regular backend processes */
7532 3707 [ # # ]: 0 : if (proc->roleId == roleid)
3708 : 0 : count++;
3709 : : }
3710 : :
3711 : 0 : LWLockRelease(ProcArrayLock);
3712 : :
3713 : 0 : return count;
3714 : : }
3715 : :
3716 : : /*
3717 : : * CountOtherDBBackends -- check for other backends running in the given DB
3718 : : *
3719 : : * If there are other backends in the DB, we will wait a maximum of 5 seconds
3720 : : * for them to exit (or 0.3s for testing purposes). Autovacuum backends are
3721 : : * encouraged to exit early by sending them SIGTERM, but normal user backends
3722 : : * are just waited for. If background workers connected to this database are
3723 : : * marked as interruptible, they are terminated.
3724 : : *
3725 : : * The current backend is always ignored; it is caller's responsibility to
3726 : : * check whether the current backend uses the given DB, if it's important.
3727 : : *
3728 : : * Returns true if there are (still) other backends in the DB, false if not.
3729 : : * Also, *nbackends and *nprepared are set to the number of other backends
3730 : : * and prepared transactions in the DB, respectively.
3731 : : *
3732 : : * This function is used to interlock DROP DATABASE and related commands
3733 : : * against there being any active backends in the target DB --- dropping the
3734 : : * DB while active backends remain would be a Bad Thing. Note that we cannot
3735 : : * detect here the possibility of a newly-started backend that is trying to
3736 : : * connect to the doomed database, so additional interlocking is needed during
3737 : : * backend startup. The caller should normally hold an exclusive lock on the
3738 : : * target DB before calling this, which is one reason we mustn't wait
3739 : : * indefinitely.
3740 : : */
3741 : : bool
6432 tgl@sss.pgh.pa.us 3742 :CBC 467 : CountOtherDBBackends(Oid databaseId, int *nbackends, int *nprepared)
3743 : : {
6862 3744 : 467 : ProcArrayStruct *arrayP = procArray;
3745 : :
3746 : : #define MAXAUTOVACPIDS 10 /* max autovacs to SIGTERM per iteration */
3747 : : int autovac_pids[MAXAUTOVACPIDS];
3748 : :
3749 : : /*
3750 : : * Retry up to 50 times with 100ms between attempts (max 5s total). Can be
3751 : : * reduced to 3 attempts (max 0.3s total) to speed up tests.
3752 : : */
68 michael@paquier.xyz 3753 :GNC 467 : int ntries = 50;
3754 : :
3755 : : #ifdef USE_INJECTION_POINTS
3756 [ + + ]: 467 : if (IS_INJECTION_POINT_ATTACHED("procarray-reduce-count"))
3757 : 1 : ntries = 3;
3758 : : #endif
3759 : :
3760 [ + + ]: 474 : for (int tries = 0; tries < ntries; tries++)
3761 : : {
6432 tgl@sss.pgh.pa.us 3762 :CBC 473 : int nautovacs = 0;
6862 3763 : 473 : bool found = false;
3764 : : int index;
3765 : :
3766 [ - + ]: 473 : CHECK_FOR_INTERRUPTS();
3767 : :
6432 3768 : 473 : *nbackends = *nprepared = 0;
3769 : :
6862 3770 : 473 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3771 : :
3772 [ + + ]: 1795 : for (index = 0; index < arrayP->numProcs; index++)
3773 : : {
5026 bruce@momjian.us 3774 : 1322 : int pgprocno = arrayP->pgprocnos[index];
2683 andres@anarazel.de 3775 : 1322 : PGPROC *proc = &allProcs[pgprocno];
1945 alvherre@alvh.no-ip. 3776 : 1322 : uint8 statusFlags = ProcGlobal->statusFlags[index];
3777 : :
6862 tgl@sss.pgh.pa.us 3778 [ + + ]: 1322 : if (proc->databaseId != databaseId)
3779 : 1212 : continue;
3780 [ + + ]: 110 : if (proc == MyProc)
3781 : 103 : continue;
3782 : :
6862 tgl@sss.pgh.pa.us 3783 :GBC 7 : found = true;
3784 : :
6432 3785 [ - + ]: 7 : if (proc->pid == 0)
6432 tgl@sss.pgh.pa.us 3786 :UBC 0 : (*nprepared)++;
3787 : : else
3788 : : {
6432 tgl@sss.pgh.pa.us 3789 :GBC 7 : (*nbackends)++;
1945 alvherre@alvh.no-ip. 3790 [ - + - - ]: 7 : if ((statusFlags & PROC_IS_AUTOVACUUM) &&
3791 : : nautovacs < MAXAUTOVACPIDS)
6432 tgl@sss.pgh.pa.us 3792 :UBC 0 : autovac_pids[nautovacs++] = proc->pid;
3793 : : }
3794 : : }
3795 : :
6432 tgl@sss.pgh.pa.us 3796 :CBC 473 : LWLockRelease(ProcArrayLock);
3797 : :
6862 3798 [ + + ]: 473 : if (!found)
6695 bruce@momjian.us 3799 : 466 : return false; /* no conflicting backends, so done */
3800 : :
3801 : : /*
3802 : : * Send SIGTERM to any conflicting autovacuums before sleeping. We
3803 : : * postpone this step until after the loop because we don't want to
3804 : : * hold ProcArrayLock while issuing kill(). We have no idea what might
3805 : : * block kill() inside the kernel...
3806 : : */
6432 tgl@sss.pgh.pa.us 3807 [ - + ]:GBC 7 : for (index = 0; index < nautovacs; index++)
6432 tgl@sss.pgh.pa.us 3808 :UBC 0 : (void) kill(autovac_pids[index], SIGTERM); /* ignore any error */
3809 : :
3810 : : /*
3811 : : * Terminate all background workers for this database, if they have
3812 : : * requested it (BGWORKER_INTERRUPTIBLE).
3813 : : */
68 michael@paquier.xyz 3814 :GNC 7 : TerminateBackgroundWorkersForDatabase(databaseId);
3815 : :
3816 : : /* sleep, then try again */
6695 bruce@momjian.us 3817 :GBC 7 : pg_usleep(100 * 1000L); /* 100ms */
3818 : : }
3819 : :
3820 : 1 : return true; /* timed out, still conflicts */
3821 : : }
3822 : :
3823 : : /*
3824 : : * Terminate existing connections to the specified database. This routine
3825 : : * is used by the DROP DATABASE command when user has asked to forcefully
3826 : : * drop the database.
3827 : : *
3828 : : * The current backend is always ignored; it is caller's responsibility to
3829 : : * check whether the current backend uses the given DB, if it's important.
3830 : : *
3831 : : * If the target database has a prepared transaction or permissions checks
3832 : : * fail for a connection, this fails without terminating anything.
3833 : : */
3834 : : void
2315 akapila@postgresql.o 3835 :CBC 1 : TerminateOtherDBBackends(Oid databaseId)
3836 : : {
3837 : 1 : ProcArrayStruct *arrayP = procArray;
3838 : 1 : List *pids = NIL;
3839 : 1 : int nprepared = 0;
3840 : : int i;
3841 : :
3842 : 1 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3843 : :
3844 [ + + ]: 4 : for (i = 0; i < procArray->numProcs; i++)
3845 : : {
3846 : 3 : int pgprocno = arrayP->pgprocnos[i];
3847 : 3 : PGPROC *proc = &allProcs[pgprocno];
3848 : :
3849 [ + - ]: 3 : if (proc->databaseId != databaseId)
3850 : 3 : continue;
2315 akapila@postgresql.o 3851 [ # # ]:UBC 0 : if (proc == MyProc)
3852 : 0 : continue;
3853 : :
3854 [ # # ]: 0 : if (proc->pid != 0)
3855 : 0 : pids = lappend_int(pids, proc->pid);
3856 : : else
3857 : 0 : nprepared++;
3858 : : }
3859 : :
2315 akapila@postgresql.o 3860 :CBC 1 : LWLockRelease(ProcArrayLock);
3861 : :
3862 [ - + ]: 1 : if (nprepared > 0)
2315 akapila@postgresql.o 3863 [ # # ]:UBC 0 : ereport(ERROR,
3864 : : (errcode(ERRCODE_OBJECT_IN_USE),
3865 : : errmsg("database \"%s\" is being used by prepared transactions",
3866 : : get_database_name(databaseId)),
3867 : : errdetail_plural("There is %d prepared transaction using the database.",
3868 : : "There are %d prepared transactions using the database.",
3869 : : nprepared,
3870 : : nprepared)));
3871 : :
2315 akapila@postgresql.o 3872 [ - + ]:CBC 1 : if (pids)
3873 : : {
3874 : : ListCell *lc;
3875 : :
3876 : : /*
3877 : : * Permissions checks relax the pg_terminate_backend checks in two
3878 : : * ways, both by omitting the !OidIsValid(proc->roleId) check:
3879 : : *
3880 : : * - Accept terminating autovacuum workers, since DROP DATABASE
3881 : : * without FORCE terminates them.
3882 : : *
3883 : : * - Accept terminating bgworkers. For bgworker authors, it's
3884 : : * convenient to be able to recommend FORCE if a worker is blocking
3885 : : * DROP DATABASE unexpectedly.
3886 : : *
3887 : : * Unlike pg_terminate_backend, we don't raise some warnings - like
3888 : : * "PID %d is not a PostgreSQL server process", because for us already
3889 : : * finished session is not a problem.
3890 : : */
2315 akapila@postgresql.o 3891 [ # # # # :UBC 0 : foreach(lc, pids)
# # ]
3892 : : {
3893 : 0 : int pid = lfirst_int(lc);
3894 : 0 : PGPROC *proc = BackendPidGetProc(pid);
3895 : :
3896 [ # # ]: 0 : if (proc != NULL)
3897 : : {
3898 [ # # # # ]: 0 : if (superuser_arg(proc->roleId) && !superuser())
3899 [ # # ]: 0 : ereport(ERROR,
3900 : : (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
3901 : : errmsg("permission denied to terminate process"),
3902 : : errdetail("Only roles with the %s attribute may terminate processes of roles with the %s attribute.",
3903 : : "SUPERUSER", "SUPERUSER")));
3904 : :
3905 [ # # ]: 0 : if (!has_privs_of_role(GetUserId(), proc->roleId) &&
1809 sfrost@snowman.net 3906 [ # # ]: 0 : !has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
2315 akapila@postgresql.o 3907 [ # # ]: 0 : ereport(ERROR,
3908 : : (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
3909 : : errmsg("permission denied to terminate process"),
3910 : : errdetail("Only roles with privileges of the role whose process is being terminated or with privileges of the \"%s\" role may terminate this process.",
3911 : : "pg_signal_backend")));
3912 : : }
3913 : : }
3914 : :
3915 : : /*
3916 : : * There's a race condition here: once we release the ProcArrayLock,
3917 : : * it's possible for the session to exit before we issue kill. That
3918 : : * race condition possibility seems too unlikely to worry about. See
3919 : : * pg_signal_backend.
3920 : : */
3921 [ # # # # : 0 : foreach(lc, pids)
# # ]
3922 : : {
3923 : 0 : int pid = lfirst_int(lc);
3924 : 0 : PGPROC *proc = BackendPidGetProc(pid);
3925 : :
3926 [ # # ]: 0 : if (proc != NULL)
3927 : : {
3928 : : /*
3929 : : * If we have setsid(), signal the backend's whole process
3930 : : * group
3931 : : */
3932 : : #ifdef HAVE_SETSID
3933 : 0 : (void) kill(-pid, SIGTERM);
3934 : : #else
3935 : : (void) kill(pid, SIGTERM);
3936 : : #endif
3937 : : }
3938 : : }
3939 : : }
2315 akapila@postgresql.o 3940 :CBC 1 : }
3941 : :
3942 : : /*
3943 : : * ProcArraySetReplicationSlotXmin
3944 : : *
3945 : : * Install limits to future computations of the xmin horizon to prevent vacuum
3946 : : * and HOT pruning from removing affected rows still needed by clients with
3947 : : * replication slots.
3948 : : */
3949 : : void
4395 rhaas@postgresql.org 3950 : 2497 : ProcArraySetReplicationSlotXmin(TransactionId xmin, TransactionId catalog_xmin,
3951 : : bool already_locked)
3952 : : {
3953 [ + + - + ]: 2497 : Assert(!already_locked || LWLockHeldByMe(ProcArrayLock));
3954 : :
3955 [ + + ]: 2497 : if (!already_locked)
3956 : 1996 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
3957 : :
4426 3958 : 2497 : procArray->replication_slot_xmin = xmin;
4395 3959 : 2497 : procArray->replication_slot_catalog_xmin = catalog_xmin;
3960 : :
3961 [ + + ]: 2497 : if (!already_locked)
3962 : 1996 : LWLockRelease(ProcArrayLock);
3963 : :
1209 alvherre@alvh.no-ip. 3964 [ + + ]: 2497 : elog(DEBUG1, "xmin required by slots: data %u, catalog %u",
3965 : : xmin, catalog_xmin);
4395 rhaas@postgresql.org 3966 : 2497 : }
3967 : :
3968 : : /*
3969 : : * ProcArrayGetReplicationSlotXmin
3970 : : *
3971 : : * Return the current slot xmin limits. That's useful to be able to remove
3972 : : * data that's older than those limits.
3973 : : */
3974 : : void
3975 : 22 : ProcArrayGetReplicationSlotXmin(TransactionId *xmin,
3976 : : TransactionId *catalog_xmin)
3977 : : {
3978 : 22 : LWLockAcquire(ProcArrayLock, LW_SHARED);
3979 : :
3980 [ - + ]: 22 : if (xmin != NULL)
4395 rhaas@postgresql.org 3981 :UBC 0 : *xmin = procArray->replication_slot_xmin;
3982 : :
4395 rhaas@postgresql.org 3983 [ + - ]:CBC 22 : if (catalog_xmin != NULL)
3984 : 22 : *catalog_xmin = procArray->replication_slot_catalog_xmin;
3985 : :
4426 3986 : 22 : LWLockRelease(ProcArrayLock);
3987 : 22 : }
3988 : :
3989 : : /*
3990 : : * XidCacheRemoveRunningXids
3991 : : *
3992 : : * Remove a bunch of TransactionIds from the list of known-running
3993 : : * subtransactions for my backend. Both the specified xid and those in
3994 : : * the xids[] array (of length nxids) are removed from the subxids cache.
3995 : : * latestXid must be the latest XID among the group.
3996 : : */
3997 : : void
6763 tgl@sss.pgh.pa.us 3998 : 668 : XidCacheRemoveRunningXids(TransactionId xid,
3999 : : int nxids, const TransactionId *xids,
4000 : : TransactionId latestXid)
4001 : : {
4002 : : int i,
4003 : : j;
4004 : : XidCacheStatus *mysubxidstat;
4005 : :
7133 4006 [ - + ]: 668 : Assert(TransactionIdIsValid(xid));
4007 : :
4008 : : /*
4009 : : * We must hold ProcArrayLock exclusively in order to remove transactions
4010 : : * from the PGPROC array. (See src/backend/access/transam/README.) It's
4011 : : * possible this could be relaxed since we know this routine is only used
4012 : : * to abort subtransactions, but pending closer analysis we'd best be
4013 : : * conservative.
4014 : : *
4015 : : * Note that we do not have to be careful about memory ordering of our own
4016 : : * reads wrt. GetNewTransactionId() here - only this process can modify
4017 : : * relevant fields of MyProc/ProcGlobal->xids[]. But we do have to be
4018 : : * careful about our own writes being well ordered.
4019 : : */
7605 4020 : 668 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
4021 : :
2039 andres@anarazel.de 4022 : 668 : mysubxidstat = &ProcGlobal->subxidStates[MyProc->pgxactoff];
4023 : :
4024 : : /*
4025 : : * Under normal circumstances xid and xids[] will be in increasing order,
4026 : : * as will be the entries in subxids. Scan backwards to avoid O(N^2)
4027 : : * behavior when removing a lot of xids.
4028 : : */
7605 tgl@sss.pgh.pa.us 4029 [ + + ]: 698 : for (i = nxids - 1; i >= 0; i--)
4030 : : {
4031 : 30 : TransactionId anxid = xids[i];
4032 : :
2039 andres@anarazel.de 4033 [ + - ]: 30 : for (j = MyProc->subxidStatus.count - 1; j >= 0; j--)
4034 : : {
7605 tgl@sss.pgh.pa.us 4035 [ + - ]: 30 : if (TransactionIdEquals(MyProc->subxids.xids[j], anxid))
4036 : : {
2039 andres@anarazel.de 4037 : 30 : MyProc->subxids.xids[j] = MyProc->subxids.xids[MyProc->subxidStatus.count - 1];
4038 : 30 : pg_write_barrier();
4039 : 30 : mysubxidstat->count--;
4040 : 30 : MyProc->subxidStatus.count--;
7605 tgl@sss.pgh.pa.us 4041 : 30 : break;
4042 : : }
4043 : : }
4044 : :
4045 : : /*
4046 : : * Ordinarily we should have found it, unless the cache has
4047 : : * overflowed. However it's also possible for this routine to be
4048 : : * invoked multiple times for the same subtransaction, in case of an
4049 : : * error during AbortSubTransaction. So instead of Assert, emit a
4050 : : * debug warning.
4051 : : */
2039 andres@anarazel.de 4052 [ - + - - ]: 30 : if (j < 0 && !MyProc->subxidStatus.overflowed)
7605 tgl@sss.pgh.pa.us 4053 [ # # ]:UBC 0 : elog(WARNING, "did not find subXID %u in MyProc", anxid);
4054 : : }
4055 : :
2039 andres@anarazel.de 4056 [ + + ]:CBC 860 : for (j = MyProc->subxidStatus.count - 1; j >= 0; j--)
4057 : : {
7605 tgl@sss.pgh.pa.us 4058 [ + + ]: 857 : if (TransactionIdEquals(MyProc->subxids.xids[j], xid))
4059 : : {
2039 andres@anarazel.de 4060 : 665 : MyProc->subxids.xids[j] = MyProc->subxids.xids[MyProc->subxidStatus.count - 1];
4061 : 665 : pg_write_barrier();
4062 : 665 : mysubxidstat->count--;
4063 : 665 : MyProc->subxidStatus.count--;
7605 tgl@sss.pgh.pa.us 4064 : 665 : break;
4065 : : }
4066 : : }
4067 : : /* Ordinarily we should have found it, unless the cache has overflowed */
2039 andres@anarazel.de 4068 [ + + - + ]: 668 : if (j < 0 && !MyProc->subxidStatus.overflowed)
7605 tgl@sss.pgh.pa.us 4069 [ # # ]:UBC 0 : elog(WARNING, "did not find subXID %u in MyProc", xid);
4070 : :
4071 : : /* Also advance global latestCompletedXid while holding the lock */
2042 andres@anarazel.de 4072 :CBC 668 : MaintainLatestCompletedXid(latestXid);
4073 : :
4074 : : /* ... and xactCompletionCount */
828 heikki.linnakangas@i 4075 : 668 : TransamVariables->xactCompletionCount++;
4076 : :
7605 tgl@sss.pgh.pa.us 4077 : 668 : LWLockRelease(ProcArrayLock);
4078 : 668 : }
4079 : :
4080 : : #ifdef XIDCACHE_DEBUG
4081 : :
4082 : : /*
4083 : : * Print stats about effectiveness of XID cache
4084 : : */
4085 : : static void
4086 : : DisplayXidCache(void)
4087 : : {
4088 : : fprintf(stderr,
4089 : : "XidCache: xmin: %ld, known: %ld, myxact: %ld, latest: %ld, mainxid: %ld, childxid: %ld, knownassigned: %ld, nooflo: %ld, slow: %ld\n",
4090 : : xc_by_recent_xmin,
4091 : : xc_by_known_xact,
4092 : : xc_by_my_xact,
4093 : : xc_by_latest_xid,
4094 : : xc_by_main_xid,
4095 : : xc_by_child_xid,
4096 : : xc_by_known_assigned,
4097 : : xc_no_overflow,
4098 : : xc_slow_answer);
4099 : : }
4100 : : #endif /* XIDCACHE_DEBUG */
4101 : :
4102 : : /*
4103 : : * If rel != NULL, return test state appropriate for relation, otherwise
4104 : : * return state usable for all relations. The latter may consider XIDs as
4105 : : * not-yet-visible-to-everyone that a state for a specific relation would
4106 : : * already consider visible-to-everyone.
4107 : : *
4108 : : * This needs to be called while a snapshot is active or registered, otherwise
4109 : : * there are wraparound and other dangers.
4110 : : *
4111 : : * See comment for GlobalVisState for details.
4112 : : */
4113 : : GlobalVisState *
2041 andres@anarazel.de 4114 : 14330888 : GlobalVisTestFor(Relation rel)
4115 : : {
1695 4116 : 14330888 : GlobalVisState *state = NULL;
4117 : :
4118 : : /* XXX: we should assert that a snapshot is pushed or registered */
2041 4119 [ - + ]: 14330888 : Assert(RecentXmin);
4120 : :
1695 4121 [ + + + + : 14330888 : switch (GlobalVisHorizonKindForRel(rel))
- ]
4122 : : {
4123 : 71180 : case VISHORIZON_SHARED:
4124 : 71180 : state = &GlobalVisSharedRels;
4125 : 71180 : break;
4126 : 2921756 : case VISHORIZON_CATALOG:
4127 : 2921756 : state = &GlobalVisCatalogRels;
4128 : 2921756 : break;
4129 : 11295989 : case VISHORIZON_DATA:
4130 : 11295989 : state = &GlobalVisDataRels;
4131 : 11295989 : break;
4132 : 41963 : case VISHORIZON_TEMP:
4133 : 41963 : state = &GlobalVisTempRels;
4134 : 41963 : break;
4135 : : }
4136 : :
2041 4137 [ + - - + ]: 14330888 : Assert(FullTransactionIdIsValid(state->definitely_needed) &&
4138 : : FullTransactionIdIsValid(state->maybe_needed));
4139 : :
4140 : 14330888 : return state;
4141 : : }
4142 : :
4143 : : /*
4144 : : * Return true if it's worth updating the accurate maybe_needed boundary.
4145 : : *
4146 : : * As it is somewhat expensive to determine xmin horizons, we don't want to
4147 : : * repeatedly do so when there is a low likelihood of it being beneficial.
4148 : : *
4149 : : * The current heuristic is that we update only if RecentXmin has changed
4150 : : * since the last update. If the oldest currently running transaction has not
4151 : : * finished, it is unlikely that recomputing the horizon would be useful.
4152 : : */
4153 : : static bool
4154 : 428992 : GlobalVisTestShouldUpdate(GlobalVisState *state)
4155 : : {
4156 : : /* hasn't been updated yet */
4157 [ + + ]: 428992 : if (!TransactionIdIsValid(ComputeXidHorizonsResultLastXmin))
4158 : 9027 : return true;
4159 : :
4160 : : /*
4161 : : * If the maybe_needed/definitely_needed boundaries are the same, it's
4162 : : * unlikely to be beneficial to refresh boundaries.
4163 : : */
4164 [ - + ]: 419965 : if (FullTransactionIdFollowsOrEquals(state->maybe_needed,
4165 : : state->definitely_needed))
2041 andres@anarazel.de 4166 :UBC 0 : return false;
4167 : :
4168 : : /* does the last snapshot built have a different xmin? */
2041 andres@anarazel.de 4169 :CBC 419965 : return RecentXmin != ComputeXidHorizonsResultLastXmin;
4170 : : }
4171 : :
4172 : : static void
4173 : 89137 : GlobalVisUpdateApply(ComputeXidHorizonsResult *horizons)
4174 : : {
4175 : : GlobalVisSharedRels.maybe_needed =
4176 : 89137 : FullXidRelativeTo(horizons->latest_completed,
4177 : : horizons->shared_oldest_nonremovable);
4178 : : GlobalVisCatalogRels.maybe_needed =
4179 : 89137 : FullXidRelativeTo(horizons->latest_completed,
4180 : : horizons->catalog_oldest_nonremovable);
4181 : : GlobalVisDataRels.maybe_needed =
4182 : 89137 : FullXidRelativeTo(horizons->latest_completed,
4183 : : horizons->data_oldest_nonremovable);
4184 : : GlobalVisTempRels.maybe_needed =
1964 4185 : 89137 : FullXidRelativeTo(horizons->latest_completed,
4186 : : horizons->temp_oldest_nonremovable);
4187 : :
4188 : : /*
4189 : : * In longer running transactions it's possible that transactions we
4190 : : * previously needed to treat as running aren't around anymore. So update
4191 : : * definitely_needed to not be earlier than maybe_needed.
4192 : : */
4193 : : GlobalVisSharedRels.definitely_needed =
2041 4194 : 89137 : FullTransactionIdNewer(GlobalVisSharedRels.maybe_needed,
4195 : : GlobalVisSharedRels.definitely_needed);
4196 : : GlobalVisCatalogRels.definitely_needed =
4197 : 89137 : FullTransactionIdNewer(GlobalVisCatalogRels.maybe_needed,
4198 : : GlobalVisCatalogRels.definitely_needed);
4199 : : GlobalVisDataRels.definitely_needed =
4200 : 89137 : FullTransactionIdNewer(GlobalVisDataRels.maybe_needed,
4201 : : GlobalVisDataRels.definitely_needed);
1964 4202 : 89137 : GlobalVisTempRels.definitely_needed = GlobalVisTempRels.maybe_needed;
4203 : :
2041 4204 : 89137 : ComputeXidHorizonsResultLastXmin = RecentXmin;
4205 : 89137 : }
4206 : :
4207 : : /*
4208 : : * Update boundaries in GlobalVis{Shared,Catalog, Data}Rels
4209 : : * using ComputeXidHorizons().
4210 : : */
4211 : : static void
4212 : 51352 : GlobalVisUpdate(void)
4213 : : {
4214 : : ComputeXidHorizonsResult horizons;
4215 : :
4216 : : /* updates the horizons as a side-effect */
4217 : 51352 : ComputeXidHorizons(&horizons);
4218 : 51352 : }
4219 : :
4220 : : /*
4221 : : * Return true if no snapshot still considers fxid to be running.
4222 : : *
4223 : : * The state passed needs to have been initialized for the relation fxid is
4224 : : * from (NULL is also OK), otherwise the result may not be correct.
4225 : : *
4226 : : * See comment for GlobalVisState for details.
4227 : : */
4228 : : bool
4229 : 9637142 : GlobalVisTestIsRemovableFullXid(GlobalVisState *state,
4230 : : FullTransactionId fxid)
4231 : : {
4232 : : /*
4233 : : * If fxid is older than maybe_needed bound, it definitely is visible to
4234 : : * everyone.
4235 : : */
4236 [ + + ]: 9637142 : if (FullTransactionIdPrecedes(fxid, state->maybe_needed))
4237 : 2413792 : return true;
4238 : :
4239 : : /*
4240 : : * If fxid is >= definitely_needed bound, it is very likely to still be
4241 : : * considered running.
4242 : : */
4243 [ + + ]: 7223350 : if (FullTransactionIdFollowsOrEquals(fxid, state->definitely_needed))
4244 : 6794358 : return false;
4245 : :
4246 : : /*
4247 : : * fxid is between maybe_needed and definitely_needed, i.e. there might or
4248 : : * might not exist a snapshot considering fxid running. If it makes sense,
4249 : : * update boundaries and recheck.
4250 : : */
4251 [ + + ]: 428992 : if (GlobalVisTestShouldUpdate(state))
4252 : : {
4253 : 51352 : GlobalVisUpdate();
4254 : :
4255 [ - + ]: 51352 : Assert(FullTransactionIdPrecedes(fxid, state->definitely_needed));
4256 : :
4257 : 51352 : return FullTransactionIdPrecedes(fxid, state->maybe_needed);
4258 : : }
4259 : : else
4260 : 377640 : return false;
4261 : : }
4262 : :
4263 : : /*
4264 : : * Wrapper around GlobalVisTestIsRemovableFullXid() for 32bit xids.
4265 : : *
4266 : : * It is crucial that this only gets called for xids from a source that
4267 : : * protects against xid wraparounds (e.g. from a table and thus protected by
4268 : : * relfrozenxid).
4269 : : */
4270 : : bool
4271 : 9634938 : GlobalVisTestIsRemovableXid(GlobalVisState *state, TransactionId xid)
4272 : : {
4273 : : FullTransactionId fxid;
4274 : :
4275 : : /*
4276 : : * Convert 32 bit argument to FullTransactionId. We can do so safely
4277 : : * because we know the xid has to, at the very least, be between
4278 : : * [oldestXid, nextXid), i.e. within 2 billion of xid. To avoid taking a
4279 : : * lock to determine either, we can just compare with
4280 : : * state->definitely_needed, which was based on those value at the time
4281 : : * the current snapshot was built.
4282 : : */
4283 : 9634938 : fxid = FullXidRelativeTo(state->definitely_needed, xid);
4284 : :
4285 : 9634938 : return GlobalVisTestIsRemovableFullXid(state, fxid);
4286 : : }
4287 : :
4288 : : /*
4289 : : * Convenience wrapper around GlobalVisTestFor() and
4290 : : * GlobalVisTestIsRemovableFullXid(), see their comments.
4291 : : */
4292 : : bool
1862 pg@bowt.ie 4293 : 2204 : GlobalVisCheckRemovableFullXid(Relation rel, FullTransactionId fxid)
4294 : : {
4295 : : GlobalVisState *state;
4296 : :
2041 andres@anarazel.de 4297 : 2204 : state = GlobalVisTestFor(rel);
4298 : :
4299 : 2204 : return GlobalVisTestIsRemovableFullXid(state, fxid);
4300 : : }
4301 : :
4302 : : /*
4303 : : * Convenience wrapper around GlobalVisTestFor() and
4304 : : * GlobalVisTestIsRemovableXid(), see their comments.
4305 : : */
4306 : : bool
4307 : 6 : GlobalVisCheckRemovableXid(Relation rel, TransactionId xid)
4308 : : {
4309 : : GlobalVisState *state;
4310 : :
4311 : 6 : state = GlobalVisTestFor(rel);
4312 : :
4313 : 6 : return GlobalVisTestIsRemovableXid(state, xid);
4314 : : }
4315 : :
4316 : : /*
4317 : : * Convert a 32 bit transaction id into 64 bit transaction id, by assuming it
4318 : : * is within MaxTransactionId / 2 of XidFromFullTransactionId(rel).
4319 : : *
4320 : : * Be very careful about when to use this function. It can only safely be used
4321 : : * when there is a guarantee that xid is within MaxTransactionId / 2 xids of
4322 : : * rel. That e.g. can be guaranteed if the caller assures a snapshot is
4323 : : * held by the backend and xid is from a table (where vacuum/freezing ensures
4324 : : * the xid has to be within that range), or if xid is from the procarray and
4325 : : * prevents xid wraparound that way.
4326 : : */
4327 : : static inline FullTransactionId
2042 4328 : 11386607 : FullXidRelativeTo(FullTransactionId rel, TransactionId xid)
4329 : : {
4330 : 11386607 : TransactionId rel_xid = XidFromFullTransactionId(rel);
4331 : :
4332 [ - + ]: 11386607 : Assert(TransactionIdIsValid(xid));
4333 [ - + ]: 11386607 : Assert(TransactionIdIsValid(rel_xid));
4334 : :
4335 : : /* not guaranteed to find issues, but likely to catch mistakes */
4336 : 11386607 : AssertTransactionIdInAllowableRange(xid);
4337 : :
4338 : 22773214 : return FullTransactionIdFromU64(U64FromFullTransactionId(rel)
4339 : 11386607 : + (int32) (xid - rel_xid));
4340 : : }
4341 : :
4342 : :
4343 : : /* ----------------------------------------------
4344 : : * KnownAssignedTransactionIds sub-module
4345 : : * ----------------------------------------------
4346 : : */
4347 : :
4348 : : /*
4349 : : * In Hot Standby mode, we maintain a list of transactions that are (or were)
4350 : : * running on the primary at the current point in WAL. These XIDs must be
4351 : : * treated as running by standby transactions, even though they are not in
4352 : : * the standby server's PGPROC array.
4353 : : *
4354 : : * We record all XIDs that we know have been assigned. That includes all the
4355 : : * XIDs seen in WAL records, plus all unobserved XIDs that we can deduce have
4356 : : * been assigned. We can deduce the existence of unobserved XIDs because we
4357 : : * know XIDs are assigned in sequence, with no gaps. The KnownAssignedXids
4358 : : * list expands as new XIDs are observed or inferred, and contracts when
4359 : : * transaction completion records arrive.
4360 : : *
4361 : : * During hot standby we do not fret too much about the distinction between
4362 : : * top-level XIDs and subtransaction XIDs. We store both together in the
4363 : : * KnownAssignedXids list. In backends, this is copied into snapshots in
4364 : : * GetSnapshotData(), taking advantage of the fact that XidInMVCCSnapshot()
4365 : : * doesn't care about the distinction either. Subtransaction XIDs are
4366 : : * effectively treated as top-level XIDs and in the typical case pg_subtrans
4367 : : * links are *not* maintained (which does not affect visibility).
4368 : : *
4369 : : * We have room in KnownAssignedXids and in snapshots to hold maxProcs *
4370 : : * (1 + PGPROC_MAX_CACHED_SUBXIDS) XIDs, so every primary transaction must
4371 : : * report its subtransaction XIDs in a WAL XLOG_XACT_ASSIGNMENT record at
4372 : : * least every PGPROC_MAX_CACHED_SUBXIDS. When we receive one of these
4373 : : * records, we mark the subXIDs as children of the top XID in pg_subtrans,
4374 : : * and then remove them from KnownAssignedXids. This prevents overflow of
4375 : : * KnownAssignedXids and snapshots, at the cost that status checks for these
4376 : : * subXIDs will take a slower path through TransactionIdIsInProgress().
4377 : : * This means that KnownAssignedXids is not necessarily complete for subXIDs,
4378 : : * though it should be complete for top-level XIDs; this is the same situation
4379 : : * that holds with respect to the PGPROC entries in normal running.
4380 : : *
4381 : : * When we throw away subXIDs from KnownAssignedXids, we need to keep track of
4382 : : * that, similarly to tracking overflow of a PGPROC's subxids array. We do
4383 : : * that by remembering the lastOverflowedXid, ie the last thrown-away subXID.
4384 : : * As long as that is within the range of interesting XIDs, we have to assume
4385 : : * that subXIDs are missing from snapshots. (Note that subXID overflow occurs
4386 : : * on primary when 65th subXID arrives, whereas on standby it occurs when 64th
4387 : : * subXID arrives - that is not an error.)
4388 : : *
4389 : : * Should a backend on primary somehow disappear before it can write an abort
4390 : : * record, then we just leave those XIDs in KnownAssignedXids. They actually
4391 : : * aborted but we think they were running; the distinction is irrelevant
4392 : : * because either way any changes done by the transaction are not visible to
4393 : : * backends in the standby. We prune KnownAssignedXids when
4394 : : * XLOG_RUNNING_XACTS arrives, to forestall possible overflow of the
4395 : : * array due to such dead XIDs.
4396 : : */
4397 : :
4398 : : /*
4399 : : * RecordKnownAssignedTransactionIds
4400 : : * Record the given XID in KnownAssignedXids, as well as any preceding
4401 : : * unobserved XIDs.
4402 : : *
4403 : : * RecordKnownAssignedTransactionIds() should be run for *every* WAL record
4404 : : * associated with a transaction. Must be called for each record after we
4405 : : * have executed StartupCLOG() et al, since we must ExtendCLOG() etc..
4406 : : *
4407 : : * Called during recovery in analogy with and in place of GetNewTransactionId()
4408 : : */
4409 : : void
5930 simon@2ndQuadrant.co 4410 : 2525808 : RecordKnownAssignedTransactionIds(TransactionId xid)
4411 : : {
5785 4412 [ - + ]: 2525808 : Assert(standbyState >= STANDBY_INITIALIZED);
5784 4413 [ - + ]: 2525808 : Assert(TransactionIdIsValid(xid));
4496 heikki.linnakangas@i 4414 [ - + ]: 2525808 : Assert(TransactionIdIsValid(latestObservedXid));
4415 : :
825 michael@paquier.xyz 4416 [ - + ]: 2525808 : elog(DEBUG4, "record known xact %u latestObservedXid %u",
4417 : : xid, latestObservedXid);
4418 : :
4419 : : /*
4420 : : * When a newly observed xid arrives, it is frequently the case that it is
4421 : : * *not* the next xid in sequence. When this occurs, we must treat the
4422 : : * intervening xids as running also.
4423 : : */
5930 simon@2ndQuadrant.co 4424 [ + + ]: 2525808 : if (TransactionIdFollows(xid, latestObservedXid))
4425 : : {
4426 : : TransactionId next_expected_xid;
4427 : :
4428 : : /*
4429 : : * Extend subtrans like we do in GetNewTransactionId() during normal
4430 : : * operation using individual extend steps. Note that we do not need
4431 : : * to extend clog since its extensions are WAL logged.
4432 : : *
4433 : : * This part has to be done regardless of standbyState since we
4434 : : * immediately start assigning subtransactions to their toplevel
4435 : : * transactions.
4436 : : */
5800 tgl@sss.pgh.pa.us 4437 : 23121 : next_expected_xid = latestObservedXid;
4496 heikki.linnakangas@i 4438 [ + + ]: 47235 : while (TransactionIdPrecedes(next_expected_xid, xid))
4439 : : {
4440 [ - + ]: 24114 : TransactionIdAdvance(next_expected_xid);
5930 simon@2ndQuadrant.co 4441 : 24114 : ExtendSUBTRANS(next_expected_xid);
4442 : : }
4496 heikki.linnakangas@i 4443 [ - + ]: 23121 : Assert(next_expected_xid == xid);
4444 : :
4445 : : /*
4446 : : * If the KnownAssignedXids machinery isn't up yet, there's nothing
4447 : : * more to do since we don't track assigned xids yet.
4448 : : */
4449 [ - + ]: 23121 : if (standbyState <= STANDBY_INITIALIZED)
4450 : : {
4496 heikki.linnakangas@i 4451 :UBC 0 : latestObservedXid = xid;
4452 : 0 : return;
4453 : : }
4454 : :
4455 : : /*
4456 : : * Add (latestObservedXid, xid] onto the KnownAssignedXids array.
4457 : : */
5800 tgl@sss.pgh.pa.us 4458 :CBC 23121 : next_expected_xid = latestObservedXid;
4459 [ - + ]: 23121 : TransactionIdAdvance(next_expected_xid);
4460 : 23121 : KnownAssignedXidsAdd(next_expected_xid, xid, false);
4461 : :
4462 : : /*
4463 : : * Now we can advance latestObservedXid
4464 : : */
5930 simon@2ndQuadrant.co 4465 : 23121 : latestObservedXid = xid;
4466 : :
4467 : : /* TransamVariables->nextXid must be beyond any observed xid */
2544 tmunro@postgresql.or 4468 : 23121 : AdvanceNextFullTransactionIdPastXid(latestObservedXid);
4469 : : }
4470 : : }
4471 : :
4472 : : /*
4473 : : * ExpireTreeKnownAssignedTransactionIds
4474 : : * Remove the given XIDs from KnownAssignedXids.
4475 : : *
4476 : : * Called during recovery in analogy with and in place of ProcArrayEndTransaction()
4477 : : */
4478 : : void
5930 simon@2ndQuadrant.co 4479 : 22585 : ExpireTreeKnownAssignedTransactionIds(TransactionId xid, int nsubxids,
4480 : : TransactionId *subxids, TransactionId max_xid)
4481 : : {
5785 4482 [ - + ]: 22585 : Assert(standbyState >= STANDBY_INITIALIZED);
4483 : :
4484 : : /*
4485 : : * Uses same locking as transaction commit
4486 : : */
5930 4487 : 22585 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
4488 : :
5800 tgl@sss.pgh.pa.us 4489 : 22585 : KnownAssignedXidsRemoveTree(xid, nsubxids, subxids);
4490 : :
4491 : : /* As in ProcArrayEndTransaction, advance latestCompletedXid */
2042 andres@anarazel.de 4492 : 22585 : MaintainLatestCompletedXidRecovery(max_xid);
4493 : :
4494 : : /* ... and xactCompletionCount */
828 heikki.linnakangas@i 4495 : 22585 : TransamVariables->xactCompletionCount++;
4496 : :
5930 simon@2ndQuadrant.co 4497 : 22585 : LWLockRelease(ProcArrayLock);
4498 : 22585 : }
4499 : :
4500 : : /*
4501 : : * ExpireAllKnownAssignedTransactionIds
4502 : : * Remove all entries in KnownAssignedXids and reset lastOverflowedXid.
4503 : : */
4504 : : void
4505 : 114 : ExpireAllKnownAssignedTransactionIds(void)
4506 : : {
4507 : : FullTransactionId latestXid;
4508 : :
4509 : 114 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
5800 tgl@sss.pgh.pa.us 4510 : 114 : KnownAssignedXidsRemovePreceding(InvalidTransactionId);
4511 : :
4512 : : /* Reset latestCompletedXid to nextXid - 1 */
357 heikki.linnakangas@i 4513 [ - + ]: 114 : Assert(FullTransactionIdIsValid(TransamVariables->nextXid));
4514 : 114 : latestXid = TransamVariables->nextXid;
4515 : 114 : FullTransactionIdRetreat(&latestXid);
4516 : 114 : TransamVariables->latestCompletedXid = latestXid;
4517 : :
4518 : : /*
4519 : : * Any transactions that were in-progress were effectively aborted, so
4520 : : * advance xactCompletionCount.
4521 : : */
4522 : 114 : TransamVariables->xactCompletionCount++;
4523 : :
4524 : : /*
4525 : : * Reset lastOverflowedXid. Currently, lastOverflowedXid has no use after
4526 : : * the call of this function. But do this for unification with what
4527 : : * ExpireOldKnownAssignedTransactionIds() do.
4528 : : */
1590 akorotkov@postgresql 4529 : 114 : procArray->lastOverflowedXid = InvalidTransactionId;
5930 simon@2ndQuadrant.co 4530 : 114 : LWLockRelease(ProcArrayLock);
4531 : 114 : }
4532 : :
4533 : : /*
4534 : : * ExpireOldKnownAssignedTransactionIds
4535 : : * Remove KnownAssignedXids entries preceding the given XID and
4536 : : * potentially reset lastOverflowedXid.
4537 : : */
4538 : : void
4539 : 824 : ExpireOldKnownAssignedTransactionIds(TransactionId xid)
4540 : : {
4541 : : TransactionId latestXid;
4542 : :
4543 : 824 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
4544 : :
4545 : : /* As in ProcArrayEndTransaction, advance latestCompletedXid */
357 heikki.linnakangas@i 4546 : 824 : latestXid = xid;
4547 [ - + ]: 824 : TransactionIdRetreat(latestXid);
4548 : 824 : MaintainLatestCompletedXidRecovery(latestXid);
4549 : :
4550 : : /* ... and xactCompletionCount */
4551 : 824 : TransamVariables->xactCompletionCount++;
4552 : :
4553 : : /*
4554 : : * Reset lastOverflowedXid if we know all transactions that have been
4555 : : * possibly running are being gone. Not doing so could cause an incorrect
4556 : : * lastOverflowedXid value, which makes extra snapshots be marked as
4557 : : * suboverflowed.
4558 : : */
1590 akorotkov@postgresql 4559 [ + + ]: 824 : if (TransactionIdPrecedes(procArray->lastOverflowedXid, xid))
4560 : 816 : procArray->lastOverflowedXid = InvalidTransactionId;
5800 tgl@sss.pgh.pa.us 4561 : 824 : KnownAssignedXidsRemovePreceding(xid);
5930 simon@2ndQuadrant.co 4562 : 824 : LWLockRelease(ProcArrayLock);
4563 : 824 : }
4564 : :
4565 : : /*
4566 : : * KnownAssignedTransactionIdsIdleMaintenance
4567 : : * Opportunistically do maintenance work when the startup process
4568 : : * is about to go idle.
4569 : : */
4570 : : void
1202 tgl@sss.pgh.pa.us 4571 : 11129 : KnownAssignedTransactionIdsIdleMaintenance(void)
4572 : : {
4573 : 11129 : KnownAssignedXidsCompress(KAX_STARTUP_PROCESS_IDLE, false);
4574 : 11129 : }
4575 : :
4576 : :
4577 : : /*
4578 : : * Private module functions to manipulate KnownAssignedXids
4579 : : *
4580 : : * There are 5 main uses of the KnownAssignedXids data structure:
4581 : : *
4582 : : * * backends taking snapshots - all valid XIDs need to be copied out
4583 : : * * backends seeking to determine presence of a specific XID
4584 : : * * startup process adding new known-assigned XIDs
4585 : : * * startup process removing specific XIDs as transactions end
4586 : : * * startup process pruning array when special WAL records arrive
4587 : : *
4588 : : * This data structure is known to be a hot spot during Hot Standby, so we
4589 : : * go to some lengths to make these operations as efficient and as concurrent
4590 : : * as possible.
4591 : : *
4592 : : * The XIDs are stored in an array in sorted order --- TransactionIdPrecedes
4593 : : * order, to be exact --- to allow binary search for specific XIDs. Note:
4594 : : * in general TransactionIdPrecedes would not provide a total order, but
4595 : : * we know that the entries present at any instant should not extend across
4596 : : * a large enough fraction of XID space to wrap around (the primary would
4597 : : * shut down for fear of XID wrap long before that happens). So it's OK to
4598 : : * use TransactionIdPrecedes as a binary-search comparator.
4599 : : *
4600 : : * It's cheap to maintain the sortedness during insertions, since new known
4601 : : * XIDs are always reported in XID order; we just append them at the right.
4602 : : *
4603 : : * To keep individual deletions cheap, we need to allow gaps in the array.
4604 : : * This is implemented by marking array elements as valid or invalid using
4605 : : * the parallel boolean array KnownAssignedXidsValid[]. A deletion is done
4606 : : * by setting KnownAssignedXidsValid[i] to false, *without* clearing the
4607 : : * XID entry itself. This preserves the property that the XID entries are
4608 : : * sorted, so we can do binary searches easily. Periodically we compress
4609 : : * out the unused entries; that's much cheaper than having to compress the
4610 : : * array immediately on every deletion.
4611 : : *
4612 : : * The actually valid items in KnownAssignedXids[] and KnownAssignedXidsValid[]
4613 : : * are those with indexes tail <= i < head; items outside this subscript range
4614 : : * have unspecified contents. When head reaches the end of the array, we
4615 : : * force compression of unused entries rather than wrapping around, since
4616 : : * allowing wraparound would greatly complicate the search logic. We maintain
4617 : : * an explicit tail pointer so that pruning of old XIDs can be done without
4618 : : * immediately moving the array contents. In most cases only a small fraction
4619 : : * of the array contains valid entries at any instant.
4620 : : *
4621 : : * Although only the startup process can ever change the KnownAssignedXids
4622 : : * data structure, we still need interlocking so that standby backends will
4623 : : * not observe invalid intermediate states. The convention is that backends
4624 : : * must hold shared ProcArrayLock to examine the array. To remove XIDs from
4625 : : * the array, the startup process must hold ProcArrayLock exclusively, for
4626 : : * the usual transactional reasons (compare commit/abort of a transaction
4627 : : * during normal running). Compressing unused entries out of the array
4628 : : * likewise requires exclusive lock. To add XIDs to the array, we just insert
4629 : : * them into slots to the right of the head pointer and then advance the head
4630 : : * pointer. This doesn't require any lock at all, but on machines with weak
4631 : : * memory ordering, we need to be careful that other processors see the array
4632 : : * element changes before they see the head pointer change. We handle this by
4633 : : * using memory barriers when reading or writing the head/tail pointers (unless
4634 : : * the caller holds ProcArrayLock exclusively).
4635 : : *
4636 : : * Algorithmic analysis:
4637 : : *
4638 : : * If we have a maximum of M slots, with N XIDs currently spread across
4639 : : * S elements then we have N <= S <= M always.
4640 : : *
4641 : : * * Adding a new XID is O(1) and needs no lock (unless compression must
4642 : : * happen)
4643 : : * * Compressing the array is O(S) and requires exclusive lock
4644 : : * * Removing an XID is O(logS) and requires exclusive lock
4645 : : * * Taking a snapshot is O(S) and requires shared lock
4646 : : * * Checking for an XID is O(logS) and requires shared lock
4647 : : *
4648 : : * In comparison, using a hash table for KnownAssignedXids would mean that
4649 : : * taking snapshots would be O(M). If we can maintain S << M then the
4650 : : * sorted array technique will deliver significantly faster snapshots.
4651 : : * If we try to keep S too small then we will spend too much time compressing,
4652 : : * so there is an optimal point for any workload mix. We use a heuristic to
4653 : : * decide when to compress the array, though trimming also helps reduce
4654 : : * frequency of compressing. The heuristic requires us to track the number of
4655 : : * currently valid XIDs in the array (N). Except in special cases, we'll
4656 : : * compress when S >= 2N. Bounding S at 2N in turn bounds the time for
4657 : : * taking a snapshot to be O(N), which it would have to be anyway.
4658 : : */
4659 : :
4660 : :
4661 : : /*
4662 : : * Compress KnownAssignedXids by shifting valid data down to the start of the
4663 : : * array, removing any gaps.
4664 : : *
4665 : : * A compression step is forced if "reason" is KAX_NO_SPACE, otherwise
4666 : : * we do it only if a heuristic indicates it's a good time to do it.
4667 : : *
4668 : : * Compression requires holding ProcArrayLock in exclusive mode.
4669 : : * Caller must pass haveLock = true if it already holds the lock.
4670 : : */
4671 : : static void
4672 : 34559 : KnownAssignedXidsCompress(KAXCompressReason reason, bool haveLock)
4673 : : {
2683 andres@anarazel.de 4674 : 34559 : ProcArrayStruct *pArray = procArray;
4675 : : int head,
4676 : : tail,
4677 : : nelements;
4678 : : int compress_index;
4679 : : int i;
4680 : :
4681 : : /* Counters for compression heuristics */
4682 : : static unsigned int transactionEndsCounter;
4683 : : static TimestampTz lastCompressTs;
4684 : :
4685 : : /* Tuning constants */
4686 : : #define KAX_COMPRESS_FREQUENCY 128 /* in transactions */
4687 : : #define KAX_COMPRESS_IDLE_INTERVAL 1000 /* in ms */
4688 : :
4689 : : /*
4690 : : * Since only the startup process modifies the head/tail pointers, we
4691 : : * don't need a lock to read them here.
4692 : : */
5800 tgl@sss.pgh.pa.us 4693 : 34559 : head = pArray->headKnownAssignedXids;
4694 : 34559 : tail = pArray->tailKnownAssignedXids;
1202 4695 : 34559 : nelements = head - tail;
4696 : :
4697 : : /*
4698 : : * If we can choose whether to compress, use a heuristic to avoid
4699 : : * compressing too often or not often enough. "Compress" here simply
4700 : : * means moving the values to the beginning of the array, so it is not as
4701 : : * complex or costly as typical data compression algorithms.
4702 : : */
4703 [ + + ]: 34559 : if (nelements == pArray->numKnownAssignedXids)
4704 : : {
4705 : : /*
4706 : : * When there are no gaps between head and tail, don't bother to
4707 : : * compress, except in the KAX_NO_SPACE case where we must compress to
4708 : : * create some space after the head.
4709 : : */
4710 [ + - ]: 16954 : if (reason != KAX_NO_SPACE)
4711 : 16954 : return;
4712 : : }
4713 [ + + ]: 17605 : else if (reason == KAX_TRANSACTION_END)
4714 : : {
4715 : : /*
4716 : : * Consider compressing only once every so many commits. Frequency
4717 : : * determined by benchmarks.
4718 : : */
4719 [ + + ]: 14505 : if ((transactionEndsCounter++) % KAX_COMPRESS_FREQUENCY != 0)
4720 : 14382 : return;
4721 : :
4722 : : /*
4723 : : * Furthermore, compress only if the used part of the array is less
4724 : : * than 50% full (see comments above).
4725 : : */
4726 [ + + ]: 123 : if (nelements < 2 * pArray->numKnownAssignedXids)
5800 4727 : 8 : return;
4728 : : }
1202 4729 [ + + ]: 3100 : else if (reason == KAX_STARTUP_PROCESS_IDLE)
4730 : : {
4731 : : /*
4732 : : * We're about to go idle for lack of new WAL, so we might as well
4733 : : * compress. But not too often, to avoid ProcArray lock contention
4734 : : * with readers.
4735 : : */
4736 [ + - ]: 2976 : if (lastCompressTs != 0)
4737 : : {
4738 : : TimestampTz compress_after;
4739 : :
4740 : 2976 : compress_after = TimestampTzPlusMilliseconds(lastCompressTs,
4741 : : KAX_COMPRESS_IDLE_INTERVAL);
4742 [ + + ]: 2976 : if (GetCurrentTimestamp() < compress_after)
4743 : 2946 : return;
4744 : : }
4745 : : }
4746 : :
4747 : : /* Need to compress, so get the lock if we don't have it. */
4748 [ + + ]: 269 : if (!haveLock)
4749 : 30 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
4750 : :
4751 : : /*
4752 : : * We compress the array by reading the valid values from tail to head,
4753 : : * re-aligning data to 0th element.
4754 : : */
5800 4755 : 269 : compress_index = 0;
4756 [ + + ]: 10348 : for (i = tail; i < head; i++)
4757 : : {
4758 [ + + ]: 10079 : if (KnownAssignedXidsValid[i])
4759 : : {
4760 : 1114 : KnownAssignedXids[compress_index] = KnownAssignedXids[i];
4761 : 1114 : KnownAssignedXidsValid[compress_index] = true;
4762 : 1114 : compress_index++;
4763 : : }
4764 : : }
1202 4765 [ - + ]: 269 : Assert(compress_index == pArray->numKnownAssignedXids);
4766 : :
5800 4767 : 269 : pArray->tailKnownAssignedXids = 0;
4768 : 269 : pArray->headKnownAssignedXids = compress_index;
4769 : :
1202 4770 [ + + ]: 269 : if (!haveLock)
4771 : 30 : LWLockRelease(ProcArrayLock);
4772 : :
4773 : : /* Update timestamp for maintenance. No need to hold lock for this. */
4774 : 269 : lastCompressTs = GetCurrentTimestamp();
4775 : : }
4776 : :
4777 : : /*
4778 : : * Add xids into KnownAssignedXids at the head of the array.
4779 : : *
4780 : : * xids from from_xid to to_xid, inclusive, are added to the array.
4781 : : *
4782 : : * If exclusive_lock is true then caller already holds ProcArrayLock in
4783 : : * exclusive mode, so we need no extra locking here. Else caller holds no
4784 : : * lock, so we need to be sure we maintain sufficient interlocks against
4785 : : * concurrent readers. (Only the startup process ever calls this, so no need
4786 : : * to worry about concurrent writers.)
4787 : : */
4788 : : static void
5800 4789 : 23126 : KnownAssignedXidsAdd(TransactionId from_xid, TransactionId to_xid,
4790 : : bool exclusive_lock)
4791 : : {
2683 andres@anarazel.de 4792 : 23126 : ProcArrayStruct *pArray = procArray;
4793 : : TransactionId next_xid;
4794 : : int head,
4795 : : tail;
4796 : : int nxids;
4797 : : int i;
4798 : :
5800 tgl@sss.pgh.pa.us 4799 [ - + ]: 23126 : Assert(TransactionIdPrecedesOrEquals(from_xid, to_xid));
4800 : :
4801 : : /*
4802 : : * Calculate how many array slots we'll need. Normally this is cheap; in
4803 : : * the unusual case where the XIDs cross the wrap point, we do it the hard
4804 : : * way.
4805 : : */
4806 [ + - ]: 23126 : if (to_xid >= from_xid)
4807 : 23126 : nxids = to_xid - from_xid + 1;
4808 : : else
4809 : : {
5800 tgl@sss.pgh.pa.us 4810 :UBC 0 : nxids = 1;
4811 : 0 : next_xid = from_xid;
4812 [ # # ]: 0 : while (TransactionIdPrecedes(next_xid, to_xid))
4813 : : {
4814 : 0 : nxids++;
4815 [ # # ]: 0 : TransactionIdAdvance(next_xid);
4816 : : }
4817 : : }
4818 : :
4819 : : /*
4820 : : * Since only the startup process modifies the head/tail pointers, we
4821 : : * don't need a lock to read them here.
4822 : : */
5800 tgl@sss.pgh.pa.us 4823 :CBC 23126 : head = pArray->headKnownAssignedXids;
4824 : 23126 : tail = pArray->tailKnownAssignedXids;
4825 : :
4826 [ + - - + ]: 23126 : Assert(head >= 0 && head <= pArray->maxKnownAssignedXids);
4827 [ + - - + ]: 23126 : Assert(tail >= 0 && tail < pArray->maxKnownAssignedXids);
4828 : :
4829 : : /*
4830 : : * Verify that insertions occur in TransactionId sequence. Note that even
4831 : : * if the last existing element is marked invalid, it must still have a
4832 : : * correctly sequenced XID value.
4833 : : */
4834 [ + + - + ]: 38763 : if (head > tail &&
4835 : 15637 : TransactionIdFollowsOrEquals(KnownAssignedXids[head - 1], from_xid))
4836 : : {
5800 tgl@sss.pgh.pa.us 4837 :UBC 0 : KnownAssignedXidsDisplay(LOG);
4838 [ # # ]: 0 : elog(ERROR, "out-of-order XID insertion in KnownAssignedXids");
4839 : : }
4840 : :
4841 : : /*
4842 : : * If our xids won't fit in the remaining space, compress out free space
4843 : : */
5800 tgl@sss.pgh.pa.us 4844 [ - + ]:CBC 23126 : if (head + nxids > pArray->maxKnownAssignedXids)
4845 : : {
1202 tgl@sss.pgh.pa.us 4846 :UBC 0 : KnownAssignedXidsCompress(KAX_NO_SPACE, exclusive_lock);
4847 : :
5800 4848 : 0 : head = pArray->headKnownAssignedXids;
4849 : : /* note: we no longer care about the tail pointer */
4850 : :
4851 : : /*
4852 : : * If it still won't fit then we're out of memory
4853 : : */
4854 [ # # ]: 0 : if (head + nxids > pArray->maxKnownAssignedXids)
2171 peter@eisentraut.org 4855 [ # # ]: 0 : elog(ERROR, "too many KnownAssignedXids");
4856 : : }
4857 : :
4858 : : /* Now we can insert the xids into the space starting at head */
5800 tgl@sss.pgh.pa.us 4859 :CBC 23126 : next_xid = from_xid;
4860 [ + + ]: 47245 : for (i = 0; i < nxids; i++)
4861 : : {
4862 : 24119 : KnownAssignedXids[head] = next_xid;
4863 : 24119 : KnownAssignedXidsValid[head] = true;
4864 [ - + ]: 24119 : TransactionIdAdvance(next_xid);
4865 : 24119 : head++;
4866 : : }
4867 : :
4868 : : /* Adjust count of number of valid entries */
4869 : 23126 : pArray->numKnownAssignedXids += nxids;
4870 : :
4871 : : /*
4872 : : * Now update the head pointer. We use a write barrier to ensure that
4873 : : * other processors see the above array updates before they see the head
4874 : : * pointer change. The barrier isn't required if we're holding
4875 : : * ProcArrayLock exclusively.
4876 : : */
922 nathan@postgresql.or 4877 [ + + ]: 23126 : if (!exclusive_lock)
4878 : 23121 : pg_write_barrier();
4879 : :
4880 : 23126 : pArray->headKnownAssignedXids = head;
5800 tgl@sss.pgh.pa.us 4881 : 23126 : }
4882 : :
4883 : : /*
4884 : : * KnownAssignedXidsSearch
4885 : : *
4886 : : * Searches KnownAssignedXids for a specific xid and optionally removes it.
4887 : : * Returns true if it was found, false if not.
4888 : : *
4889 : : * Caller must hold ProcArrayLock in shared or exclusive mode.
4890 : : * Exclusive lock must be held for remove = true.
4891 : : */
4892 : : static bool
4893 : 25254 : KnownAssignedXidsSearch(TransactionId xid, bool remove)
4894 : : {
2683 andres@anarazel.de 4895 : 25254 : ProcArrayStruct *pArray = procArray;
4896 : : int first,
4897 : : last;
4898 : : int head;
4899 : : int tail;
5731 bruce@momjian.us 4900 : 25254 : int result_index = -1;
4901 : :
922 nathan@postgresql.or 4902 : 25254 : tail = pArray->tailKnownAssignedXids;
4903 : 25254 : head = pArray->headKnownAssignedXids;
4904 : :
4905 : : /*
4906 : : * Only the startup process removes entries, so we don't need the read
4907 : : * barrier in that case.
4908 : : */
4909 [ + + ]: 25254 : if (!remove)
4910 : 1 : pg_read_barrier(); /* pairs with KnownAssignedXidsAdd */
4911 : :
4912 : : /*
4913 : : * Standard binary search. Note we can ignore the KnownAssignedXidsValid
4914 : : * array here, since even invalid entries will contain sorted XIDs.
4915 : : */
5800 tgl@sss.pgh.pa.us 4916 : 25254 : first = tail;
4917 : 25254 : last = head - 1;
4918 [ + + ]: 89567 : while (first <= last)
4919 : : {
4920 : : int mid_index;
4921 : : TransactionId mid_xid;
4922 : :
4923 : 88358 : mid_index = (first + last) / 2;
4924 : 88358 : mid_xid = KnownAssignedXids[mid_index];
4925 : :
4926 [ + + ]: 88358 : if (xid == mid_xid)
4927 : : {
4928 : 24045 : result_index = mid_index;
4929 : 24045 : break;
4930 : : }
4931 [ + + ]: 64313 : else if (TransactionIdPrecedes(xid, mid_xid))
4932 : 13619 : last = mid_index - 1;
4933 : : else
4934 : 50694 : first = mid_index + 1;
4935 : : }
4936 : :
4937 [ + + ]: 25254 : if (result_index < 0)
4938 : 1209 : return false; /* not in array */
4939 : :
4940 [ + + ]: 24045 : if (!KnownAssignedXidsValid[result_index])
4941 : 12 : return false; /* in array, but invalid */
4942 : :
4943 [ + - ]: 24033 : if (remove)
4944 : : {
4945 : 24033 : KnownAssignedXidsValid[result_index] = false;
4946 : :
4947 : 24033 : pArray->numKnownAssignedXids--;
4948 [ - + ]: 24033 : Assert(pArray->numKnownAssignedXids >= 0);
4949 : :
4950 : : /*
4951 : : * If we're removing the tail element then advance tail pointer over
4952 : : * any invalid elements. This will speed future searches.
4953 : : */
4954 [ + + ]: 24033 : if (result_index == tail)
4955 : : {
4956 : 8630 : tail++;
4957 [ + + + + ]: 15068 : while (tail < head && !KnownAssignedXidsValid[tail])
4958 : 6438 : tail++;
4959 [ + + ]: 8630 : if (tail >= head)
4960 : : {
4961 : : /* Array is empty, so we can reset both pointers */
4962 : 7479 : pArray->headKnownAssignedXids = 0;
4963 : 7479 : pArray->tailKnownAssignedXids = 0;
4964 : : }
4965 : : else
4966 : : {
4967 : 1151 : pArray->tailKnownAssignedXids = tail;
4968 : : }
4969 : : }
4970 : : }
4971 : :
4972 : 24033 : return true;
4973 : : }
4974 : :
4975 : : /*
4976 : : * Is the specified XID present in KnownAssignedXids[]?
4977 : : *
4978 : : * Caller must hold ProcArrayLock in shared or exclusive mode.
4979 : : */
4980 : : static bool
4981 : 1 : KnownAssignedXidExists(TransactionId xid)
4982 : : {
4983 [ - + ]: 1 : Assert(TransactionIdIsValid(xid));
4984 : :
4985 : 1 : return KnownAssignedXidsSearch(xid, false);
4986 : : }
4987 : :
4988 : : /*
4989 : : * Remove the specified XID from KnownAssignedXids[].
4990 : : *
4991 : : * Caller must hold ProcArrayLock in exclusive mode.
4992 : : */
4993 : : static void
5930 simon@2ndQuadrant.co 4994 : 25253 : KnownAssignedXidsRemove(TransactionId xid)
4995 : : {
4996 [ - + ]: 25253 : Assert(TransactionIdIsValid(xid));
4997 : :
825 michael@paquier.xyz 4998 [ - + ]: 25253 : elog(DEBUG4, "remove KnownAssignedXid %u", xid);
4999 : :
5000 : : /*
5001 : : * Note: we cannot consider it an error to remove an XID that's not
5002 : : * present. We intentionally remove subxact IDs while processing
5003 : : * XLOG_XACT_ASSIGNMENT, to avoid array overflow. Then those XIDs will be
5004 : : * removed again when the top-level xact commits or aborts.
5005 : : *
5006 : : * It might be possible to track such XIDs to distinguish this case from
5007 : : * actual errors, but it would be complicated and probably not worth it.
5008 : : * So, just ignore the search result.
5009 : : */
5800 tgl@sss.pgh.pa.us 5010 : 25253 : (void) KnownAssignedXidsSearch(xid, true);
5930 simon@2ndQuadrant.co 5011 : 25253 : }
5012 : :
5013 : : /*
5014 : : * KnownAssignedXidsRemoveTree
5015 : : * Remove xid (if it's not InvalidTransactionId) and all the subxids.
5016 : : *
5017 : : * Caller must hold ProcArrayLock in exclusive mode.
5018 : : */
5019 : : static void
5800 tgl@sss.pgh.pa.us 5020 : 22606 : KnownAssignedXidsRemoveTree(TransactionId xid, int nsubxids,
5021 : : TransactionId *subxids)
5022 : : {
5023 : : int i;
5024 : :
5025 [ + + ]: 22606 : if (TransactionIdIsValid(xid))
5026 : 22585 : KnownAssignedXidsRemove(xid);
5027 : :
5028 [ + + ]: 25274 : for (i = 0; i < nsubxids; i++)
5029 : 2668 : KnownAssignedXidsRemove(subxids[i]);
5030 : :
5031 : : /* Opportunistically compress the array */
1202 5032 : 22606 : KnownAssignedXidsCompress(KAX_TRANSACTION_END, true);
5930 simon@2ndQuadrant.co 5033 : 22606 : }
5034 : :
5035 : : /*
5036 : : * Prune KnownAssignedXids up to, but *not* including xid. If xid is invalid
5037 : : * then clear the whole table.
5038 : : *
5039 : : * Caller must hold ProcArrayLock in exclusive mode.
5040 : : */
5041 : : static void
5800 tgl@sss.pgh.pa.us 5042 : 938 : KnownAssignedXidsRemovePreceding(TransactionId removeXid)
5043 : : {
2683 andres@anarazel.de 5044 : 938 : ProcArrayStruct *pArray = procArray;
5731 bruce@momjian.us 5045 : 938 : int count = 0;
5046 : : int head,
5047 : : tail,
5048 : : i;
5049 : :
5800 tgl@sss.pgh.pa.us 5050 [ + + ]: 938 : if (!TransactionIdIsValid(removeXid))
5051 : : {
825 michael@paquier.xyz 5052 [ - + ]: 114 : elog(DEBUG4, "removing all KnownAssignedXids");
5800 tgl@sss.pgh.pa.us 5053 : 114 : pArray->numKnownAssignedXids = 0;
5054 : 114 : pArray->headKnownAssignedXids = pArray->tailKnownAssignedXids = 0;
5055 : 114 : return;
5056 : : }
5057 : :
825 michael@paquier.xyz 5058 [ - + ]: 824 : elog(DEBUG4, "prune KnownAssignedXids to %u", removeXid);
5059 : :
5060 : : /*
5061 : : * Mark entries invalid starting at the tail. Since array is sorted, we
5062 : : * can stop as soon as we reach an entry >= removeXid.
5063 : : */
5800 tgl@sss.pgh.pa.us 5064 : 824 : tail = pArray->tailKnownAssignedXids;
5065 : 824 : head = pArray->headKnownAssignedXids;
5066 : :
5067 [ + + ]: 824 : for (i = tail; i < head; i++)
5068 : : {
5069 [ + - ]: 217 : if (KnownAssignedXidsValid[i])
5070 : : {
5731 bruce@momjian.us 5071 : 217 : TransactionId knownXid = KnownAssignedXids[i];
5072 : :
5800 tgl@sss.pgh.pa.us 5073 [ + - ]: 217 : if (TransactionIdFollowsOrEquals(knownXid, removeXid))
5074 : 217 : break;
5075 : :
5800 tgl@sss.pgh.pa.us 5076 [ # # ]:UBC 0 : if (!StandbyTransactionIdIsPrepared(knownXid))
5077 : : {
5078 : 0 : KnownAssignedXidsValid[i] = false;
5079 : 0 : count++;
5080 : : }
5081 : : }
5082 : : }
5083 : :
5800 tgl@sss.pgh.pa.us 5084 :CBC 824 : pArray->numKnownAssignedXids -= count;
5085 [ - + ]: 824 : Assert(pArray->numKnownAssignedXids >= 0);
5086 : :
5087 : : /*
5088 : : * Advance the tail pointer if we've marked the tail item invalid.
5089 : : */
5090 [ + + ]: 824 : for (i = tail; i < head; i++)
5091 : : {
5092 [ + - ]: 217 : if (KnownAssignedXidsValid[i])
5093 : 217 : break;
5094 : : }
5095 [ + + ]: 824 : if (i >= head)
5096 : : {
5097 : : /* Array is empty, so we can reset both pointers */
5098 : 607 : pArray->headKnownAssignedXids = 0;
5099 : 607 : pArray->tailKnownAssignedXids = 0;
5100 : : }
5101 : : else
5102 : : {
5103 : 217 : pArray->tailKnownAssignedXids = i;
5104 : : }
5105 : :
5106 : : /* Opportunistically compress the array */
1202 5107 : 824 : KnownAssignedXidsCompress(KAX_PRUNE, true);
5108 : : }
5109 : :
5110 : : /*
5111 : : * KnownAssignedXidsGet - Get an array of xids by scanning KnownAssignedXids.
5112 : : * We filter out anything >= xmax.
5113 : : *
5114 : : * Returns the number of XIDs stored into xarray[]. Caller is responsible
5115 : : * that array is large enough.
5116 : : *
5117 : : * Caller must hold ProcArrayLock in (at least) shared mode.
5118 : : */
5119 : : static int
5800 tgl@sss.pgh.pa.us 5120 :UBC 0 : KnownAssignedXidsGet(TransactionId *xarray, TransactionId xmax)
5121 : : {
5122 : 0 : TransactionId xtmp = InvalidTransactionId;
5123 : :
5124 : 0 : return KnownAssignedXidsGetAndSetXmin(xarray, &xtmp, xmax);
5125 : : }
5126 : :
5127 : : /*
5128 : : * KnownAssignedXidsGetAndSetXmin - as KnownAssignedXidsGet, plus
5129 : : * we reduce *xmin to the lowest xid value seen if not already lower.
5130 : : *
5131 : : * Caller must hold ProcArrayLock in (at least) shared mode.
5132 : : */
5133 : : static int
5800 tgl@sss.pgh.pa.us 5134 :CBC 1268 : KnownAssignedXidsGetAndSetXmin(TransactionId *xarray, TransactionId *xmin,
5135 : : TransactionId xmax)
5136 : : {
5137 : 1268 : int count = 0;
5138 : : int head,
5139 : : tail;
5140 : : int i;
5141 : :
5142 : : /*
5143 : : * Fetch head just once, since it may change while we loop. We can stop
5144 : : * once we reach the initially seen head, since we are certain that an xid
5145 : : * cannot enter and then leave the array while we hold ProcArrayLock. We
5146 : : * might miss newly-added xids, but they should be >= xmax so irrelevant
5147 : : * anyway.
5148 : : */
3803 rhaas@postgresql.org 5149 : 1268 : tail = procArray->tailKnownAssignedXids;
5150 : 1268 : head = procArray->headKnownAssignedXids;
5151 : :
922 nathan@postgresql.or 5152 : 1268 : pg_read_barrier(); /* pairs with KnownAssignedXidsAdd */
5153 : :
5800 tgl@sss.pgh.pa.us 5154 [ + + ]: 1293 : for (i = tail; i < head; i++)
5155 : : {
5156 : : /* Skip any gaps in the array */
5157 [ + + ]: 154 : if (KnownAssignedXidsValid[i])
5158 : : {
5159 : 144 : TransactionId knownXid = KnownAssignedXids[i];
5160 : :
5161 : : /*
5162 : : * Update xmin if required. Only the first XID need be checked,
5163 : : * since the array is sorted.
5164 : : */
5165 [ + - + + ]: 288 : if (count == 0 &&
5166 : 144 : TransactionIdPrecedes(knownXid, *xmin))
5167 : 15 : *xmin = knownXid;
5168 : :
5169 : : /*
5170 : : * Filter out anything >= xmax, again relying on sorted property
5171 : : * of array.
5172 : : */
5785 simon@2ndQuadrant.co 5173 [ + - + + ]: 288 : if (TransactionIdIsValid(xmax) &&
5174 : 144 : TransactionIdFollowsOrEquals(knownXid, xmax))
5800 tgl@sss.pgh.pa.us 5175 : 129 : break;
5176 : :
5177 : : /* Add knownXid into output array */
5178 : 15 : xarray[count++] = knownXid;
5179 : : }
5180 : : }
5181 : :
5182 : 1268 : return count;
5183 : : }
5184 : :
5185 : : /*
5186 : : * Get oldest XID in the KnownAssignedXids array, or InvalidTransactionId
5187 : : * if nothing there.
5188 : : */
5189 : : static TransactionId
5676 simon@2ndQuadrant.co 5190 : 365 : KnownAssignedXidsGetOldestXmin(void)
5191 : : {
5192 : : int head,
5193 : : tail;
5194 : : int i;
5195 : :
5196 : : /*
5197 : : * Fetch head just once, since it may change while we loop.
5198 : : */
3803 rhaas@postgresql.org 5199 : 365 : tail = procArray->tailKnownAssignedXids;
5200 : 365 : head = procArray->headKnownAssignedXids;
5201 : :
922 nathan@postgresql.or 5202 : 365 : pg_read_barrier(); /* pairs with KnownAssignedXidsAdd */
5203 : :
5676 simon@2ndQuadrant.co 5204 [ + + ]: 365 : for (i = tail; i < head; i++)
5205 : : {
5206 : : /* Skip any gaps in the array */
5207 [ + - ]: 145 : if (KnownAssignedXidsValid[i])
5208 : 145 : return KnownAssignedXids[i];
5209 : : }
5210 : :
5211 : 220 : return InvalidTransactionId;
5212 : : }
5213 : :
5214 : : /*
5215 : : * Display KnownAssignedXids to provide debug trail
5216 : : *
5217 : : * Currently this is only called within startup process, so we need no
5218 : : * special locking.
5219 : : *
5220 : : * Note this is pretty expensive, and much of the expense will be incurred
5221 : : * even if the elog message will get discarded. It's not currently called
5222 : : * in any performance-critical places, however, so no need to be tenser.
5223 : : */
5224 : : static void
5930 5225 : 119 : KnownAssignedXidsDisplay(int trace_level)
5226 : : {
2683 andres@anarazel.de 5227 : 119 : ProcArrayStruct *pArray = procArray;
5228 : : StringInfoData buf;
5229 : : int head,
5230 : : tail,
5231 : : i;
5731 bruce@momjian.us 5232 : 119 : int nxids = 0;
5233 : :
5800 tgl@sss.pgh.pa.us 5234 : 119 : tail = pArray->tailKnownAssignedXids;
5235 : 119 : head = pArray->headKnownAssignedXids;
5236 : :
5930 simon@2ndQuadrant.co 5237 : 119 : initStringInfo(&buf);
5238 : :
5800 tgl@sss.pgh.pa.us 5239 [ + + ]: 129 : for (i = tail; i < head; i++)
5240 : : {
5241 [ + - ]: 10 : if (KnownAssignedXidsValid[i])
5242 : : {
5243 : 10 : nxids++;
5694 rhaas@postgresql.org 5244 : 10 : appendStringInfo(&buf, "[%d]=%u ", i, KnownAssignedXids[i]);
5245 : : }
5246 : : }
5247 : :
5248 [ - + ]: 119 : elog(trace_level, "%d KnownAssignedXids (num=%d tail=%d head=%d) %s",
5249 : : nxids,
5250 : : pArray->numKnownAssignedXids,
5251 : : pArray->tailKnownAssignedXids,
5252 : : pArray->headKnownAssignedXids,
5253 : : buf.data);
5254 : :
5930 simon@2ndQuadrant.co 5255 : 119 : pfree(buf.data);
5256 : 119 : }
5257 : :
5258 : : /*
5259 : : * KnownAssignedXidsReset
5260 : : * Resets KnownAssignedXids to be empty
5261 : : */
5262 : : static void
5028 simon@2ndQuadrant.co 5263 :UBC 0 : KnownAssignedXidsReset(void)
5264 : : {
2683 andres@anarazel.de 5265 : 0 : ProcArrayStruct *pArray = procArray;
5266 : :
5028 simon@2ndQuadrant.co 5267 : 0 : LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
5268 : :
5269 : 0 : pArray->numKnownAssignedXids = 0;
5270 : 0 : pArray->tailKnownAssignedXids = 0;
5271 : 0 : pArray->headKnownAssignedXids = 0;
5272 : :
5273 : 0 : LWLockRelease(ProcArrayLock);
5274 : 0 : }
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