Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * nbtsearch.c
4 : : * Search code for postgres btrees.
5 : : *
6 : : *
7 : : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 : : * Portions Copyright (c) 1994, Regents of the University of California
9 : : *
10 : : * IDENTIFICATION
11 : : * src/backend/access/nbtree/nbtsearch.c
12 : : *
13 : : *-------------------------------------------------------------------------
14 : : */
15 : :
16 : : #include "postgres.h"
17 : :
18 : : #include "access/nbtree.h"
19 : : #include "access/relscan.h"
20 : : #include "access/xact.h"
21 : : #include "miscadmin.h"
22 : : #include "pgstat.h"
23 : : #include "storage/predicate.h"
24 : : #include "utils/lsyscache.h"
25 : : #include "utils/rel.h"
26 : :
27 : :
28 : : static inline void _bt_drop_lock_and_maybe_pin(Relation rel, BTScanOpaque so);
29 : : static Buffer _bt_moveright(Relation rel, Relation heaprel, BTScanInsert key,
30 : : Buffer buf, bool forupdate, BTStack stack,
31 : : int access);
32 : : static OffsetNumber _bt_binsrch(Relation rel, BTScanInsert key, Buffer buf);
33 : : static int _bt_binsrch_posting(BTScanInsert key, Page page,
34 : : OffsetNumber offnum);
35 : : static inline void _bt_returnitem(IndexScanDesc scan, BTScanOpaque so);
36 : : static bool _bt_steppage(IndexScanDesc scan, ScanDirection dir);
37 : : static bool _bt_readfirstpage(IndexScanDesc scan, OffsetNumber offnum,
38 : : ScanDirection dir);
39 : : static bool _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno,
40 : : BlockNumber lastcurrblkno, ScanDirection dir,
41 : : bool seized);
42 : : static Buffer _bt_lock_and_validate_left(Relation rel, BlockNumber *blkno,
43 : : BlockNumber lastcurrblkno);
44 : : static bool _bt_endpoint(IndexScanDesc scan, ScanDirection dir);
45 : :
46 : :
47 : : /*
48 : : * _bt_drop_lock_and_maybe_pin()
49 : : *
50 : : * Unlock so->currPos.buf. If scan is so->dropPin, drop the pin, too.
51 : : * Dropping the pin prevents VACUUM from blocking on acquiring a cleanup lock.
52 : : */
53 : : static inline void
193 pg@bowt.ie 54 :CBC 5038652 : _bt_drop_lock_and_maybe_pin(Relation rel, BTScanOpaque so)
55 : : {
56 [ + + ]: 5038652 : if (!so->dropPin)
57 : : {
58 : : /* Just drop the lock (not the pin) */
59 : 253067 : _bt_unlockbuf(rel, so->currPos.buf);
60 : 253067 : return;
61 : : }
62 : :
63 : : /*
64 : : * Drop both the lock and the pin.
65 : : *
66 : : * Have to set so->currPos.lsn so that _bt_killitems has a way to detect
67 : : * when concurrent heap TID recycling by VACUUM might have taken place.
68 : : */
69 [ + - + + : 4785585 : Assert(RelationNeedsWAL(rel));
+ - - + ]
70 : 4785585 : so->currPos.lsn = BufferGetLSNAtomic(so->currPos.buf);
71 : 4785585 : _bt_relbuf(rel, so->currPos.buf);
72 : 4785585 : so->currPos.buf = InvalidBuffer;
73 : : }
74 : :
75 : : /*
76 : : * _bt_search() -- Search the tree for a particular scankey,
77 : : * or more precisely for the first leaf page it could be on.
78 : : *
79 : : * The passed scankey is an insertion-type scankey (see nbtree/README),
80 : : * but it can omit the rightmost column(s) of the index.
81 : : *
82 : : * Return value is a stack of parent-page pointers (i.e. there is no entry for
83 : : * the leaf level/page). *bufP is set to the address of the leaf-page buffer,
84 : : * which is locked and pinned. No locks are held on the parent pages,
85 : : * however!
86 : : *
87 : : * The returned buffer is locked according to access parameter. Additionally,
88 : : * access = BT_WRITE will allow an empty root page to be created and returned.
89 : : * When access = BT_READ, an empty index will result in *bufP being set to
90 : : * InvalidBuffer. Also, in BT_WRITE mode, any incomplete splits encountered
91 : : * during the search will be finished.
92 : : *
93 : : * heaprel must be provided by callers that pass access = BT_WRITE, since we
94 : : * might need to allocate a new root page for caller -- see _bt_allocbuf.
95 : : */
96 : : BTStack
990 andres@anarazel.de 97 : 11250493 : _bt_search(Relation rel, Relation heaprel, BTScanInsert key, Buffer *bufP,
98 : : int access)
99 : : {
9035 bruce@momjian.us 100 : 11250493 : BTStack stack_in = NULL;
2698 akorotkov@postgresql 101 : 11250493 : int page_access = BT_READ;
102 : :
103 : : /* heaprel must be set whenever _bt_allocbuf is reachable */
920 pg@bowt.ie 104 [ + + - + ]: 11250493 : Assert(access == BT_READ || access == BT_WRITE);
105 [ + + - + ]: 11250493 : Assert(access == BT_READ || heaprel != NULL);
106 : :
107 : : /* Get the root page to start with */
990 andres@anarazel.de 108 : 11250493 : *bufP = _bt_getroot(rel, heaprel, access);
109 : :
110 : : /* If index is empty and access = BT_READ, no root page is created. */
9035 bruce@momjian.us 111 [ + + ]: 11250493 : if (!BufferIsValid(*bufP))
9279 tgl@sss.pgh.pa.us 112 : 262847 : return (BTStack) NULL;
113 : :
114 : : /* Loop iterates once per level descended in the tree */
115 : : for (;;)
116 : 9116162 : {
117 : : Page page;
118 : : BTPageOpaque opaque;
119 : : OffsetNumber offnum;
120 : : ItemId itemid;
121 : : IndexTuple itup;
122 : : BlockNumber child;
123 : : BTStack new_stack;
124 : :
125 : : /*
126 : : * Race -- the page we just grabbed may have split since we read its
127 : : * downlink in its parent page (or the metapage). If it has, we may
128 : : * need to move right to its new sibling. Do that.
129 : : *
130 : : * In write-mode, allow _bt_moveright to finish any incomplete splits
131 : : * along the way. Strictly speaking, we'd only need to finish an
132 : : * incomplete split on the leaf page we're about to insert to, not on
133 : : * any of the upper levels (internal pages with incomplete splits are
134 : : * also taken care of in _bt_getstackbuf). But this is a good
135 : : * opportunity to finish splits of internal pages too.
136 : : */
990 andres@anarazel.de 137 : 20103808 : *bufP = _bt_moveright(rel, heaprel, key, *bufP, (access == BT_WRITE),
138 : : stack_in, page_access);
139 : :
140 : : /* if this is a leaf page, we're done */
3527 kgrittn@postgresql.o 141 : 20103808 : page = BufferGetPage(*bufP);
1355 michael@paquier.xyz 142 : 20103808 : opaque = BTPageGetOpaque(page);
9279 tgl@sss.pgh.pa.us 143 [ + + ]: 20103808 : if (P_ISLEAF(opaque))
144 : 10987646 : break;
145 : :
146 : : /*
147 : : * Find the appropriate pivot tuple on this page. Its downlink points
148 : : * to the child page that we're about to descend to.
149 : : */
2463 pg@bowt.ie 150 : 9116162 : offnum = _bt_binsrch(rel, key, *bufP);
9279 tgl@sss.pgh.pa.us 151 : 9116162 : itemid = PageGetItemId(page, offnum);
7265 152 : 9116162 : itup = (IndexTuple) PageGetItem(page, itemid);
2120 pg@bowt.ie 153 [ - + - - ]: 9116162 : Assert(BTreeTupleIsPivot(itup) || !key->heapkeyspace);
1993 154 : 9116162 : child = BTreeTupleGetDownLink(itup);
155 : :
156 : : /*
157 : : * We need to save the location of the pivot tuple we chose in a new
158 : : * stack entry for this page/level. If caller ends up splitting a
159 : : * page one level down, it usually ends up inserting a new pivot
160 : : * tuple/downlink immediately after the location recorded here.
161 : : */
6 michael@paquier.xyz 162 :GNC 9116162 : new_stack = (BTStack) palloc_object(BTStackData);
1993 pg@bowt.ie 163 :CBC 9116162 : new_stack->bts_blkno = BufferGetBlockNumber(*bufP);
9279 tgl@sss.pgh.pa.us 164 : 9116162 : new_stack->bts_offset = offnum;
165 : 9116162 : new_stack->bts_parent = stack_in;
166 : :
167 : : /*
168 : : * Page level 1 is lowest non-leaf page level prior to leaves. So, if
169 : : * we're on the level 1 and asked to lock leaf page in write mode,
170 : : * then lock next page in write mode, because it must be a leaf.
171 : : */
1756 pg@bowt.ie 172 [ + + + + ]: 9116162 : if (opaque->btpo_level == 1 && access == BT_WRITE)
2698 akorotkov@postgresql 173 : 3271646 : page_access = BT_WRITE;
174 : :
175 : : /* drop the read lock on the page, then acquire one on its child */
1993 pg@bowt.ie 176 : 9116162 : *bufP = _bt_relandgetbuf(rel, *bufP, child, page_access);
177 : :
178 : : /* okay, all set to move down a level */
9279 tgl@sss.pgh.pa.us 179 : 9116162 : stack_in = new_stack;
180 : : }
181 : :
182 : : /*
183 : : * If we're asked to lock leaf in write mode, but didn't manage to, then
184 : : * relock. This should only happen when the root page is a leaf page (and
185 : : * the only page in the index other than the metapage).
186 : : */
2698 akorotkov@postgresql 187 [ + + + + ]: 10987646 : if (access == BT_WRITE && page_access == BT_READ)
188 : : {
189 : : /* trade in our read lock for a write lock */
1974 pg@bowt.ie 190 : 455120 : _bt_unlockbuf(rel, *bufP);
191 : 455120 : _bt_lockbuf(rel, *bufP, BT_WRITE);
192 : :
193 : : /*
194 : : * Race -- the leaf page may have split after we dropped the read lock
195 : : * but before we acquired a write lock. If it has, we may need to
196 : : * move right to its new sibling. Do that.
197 : : */
830 tmunro@postgresql.or 198 : 455120 : *bufP = _bt_moveright(rel, heaprel, key, *bufP, true, stack_in, BT_WRITE);
199 : : }
200 : :
9279 tgl@sss.pgh.pa.us 201 : 10987646 : return stack_in;
202 : : }
203 : :
204 : : /*
205 : : * _bt_moveright() -- move right in the btree if necessary.
206 : : *
207 : : * When we follow a pointer to reach a page, it is possible that
208 : : * the page has changed in the meanwhile. If this happens, we're
209 : : * guaranteed that the page has "split right" -- that is, that any
210 : : * data that appeared on the page originally is either on the page
211 : : * or strictly to the right of it.
212 : : *
213 : : * This routine decides whether or not we need to move right in the
214 : : * tree by examining the high key entry on the page. If that entry is
215 : : * strictly less than the scankey, or <= the scankey in the
216 : : * key.nextkey=true case, then we followed the wrong link and we need
217 : : * to move right.
218 : : *
219 : : * The passed insertion-type scankey can omit the rightmost column(s) of the
220 : : * index. (see nbtree/README)
221 : : *
222 : : * When key.nextkey is false (the usual case), we are looking for the first
223 : : * item >= key. When key.nextkey is true, we are looking for the first item
224 : : * strictly greater than key.
225 : : *
226 : : * If forupdate is true, we will attempt to finish any incomplete splits
227 : : * that we encounter. This is required when locking a target page for an
228 : : * insertion, because we don't allow inserting on a page before the split is
229 : : * completed. 'heaprel' and 'stack' are only used if forupdate is true.
230 : : *
231 : : * On entry, we have the buffer pinned and a lock of the type specified by
232 : : * 'access'. If we move right, we release the buffer and lock and acquire
233 : : * the same on the right sibling. Return value is the buffer we stop at.
234 : : */
235 : : static Buffer
10752 scrappy@hub.org 236 : 20558928 : _bt_moveright(Relation rel,
237 : : Relation heaprel,
238 : : BTScanInsert key,
239 : : Buffer buf,
240 : : bool forupdate,
241 : : BTStack stack,
242 : : int access)
243 : : {
244 : : Page page;
245 : : BTPageOpaque opaque;
246 : : int32 cmpval;
247 : :
920 pg@bowt.ie 248 [ + + - + ]: 20558928 : Assert(!forupdate || heaprel != NULL);
249 : :
250 : : /*
251 : : * When nextkey = false (normal case): if the scan key that brought us to
252 : : * this page is > the high key stored on the page, then the page has split
253 : : * and we need to move right. (pg_upgrade'd !heapkeyspace indexes could
254 : : * have some duplicates to the right as well as the left, but that's
255 : : * something that's only ever dealt with on the leaf level, after
256 : : * _bt_search has found an initial leaf page.)
257 : : *
258 : : * When nextkey = true: move right if the scan key is >= page's high key.
259 : : * (Note that key.scantid cannot be set in this case.)
260 : : *
261 : : * The page could even have split more than once, so scan as far as
262 : : * needed.
263 : : *
264 : : * We also have to move right if we followed a link that brought us to a
265 : : * dead page.
266 : : */
2463 267 : 20558928 : cmpval = key->nextkey ? 0 : 1;
268 : :
269 : : for (;;)
270 : : {
3527 kgrittn@postgresql.o 271 : 20559766 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 272 : 20559766 : opaque = BTPageGetOpaque(page);
273 : :
4291 heikki.linnakangas@i 274 [ + + ]: 20559766 : if (P_RIGHTMOST(opaque))
275 : 15764257 : break;
276 : :
277 : : /*
278 : : * Finish any incomplete splits we encounter along the way.
279 : : */
280 [ + + - + ]: 4795509 : if (forupdate && P_INCOMPLETE_SPLIT(opaque))
4291 heikki.linnakangas@i 281 :UBC 0 : {
282 : 0 : BlockNumber blkno = BufferGetBlockNumber(buf);
283 : :
284 : : /* upgrade our lock if necessary */
285 [ # # ]: 0 : if (access == BT_READ)
286 : : {
1974 pg@bowt.ie 287 : 0 : _bt_unlockbuf(rel, buf);
288 : 0 : _bt_lockbuf(rel, buf, BT_WRITE);
289 : : }
290 : :
4291 heikki.linnakangas@i 291 [ # # ]: 0 : if (P_INCOMPLETE_SPLIT(opaque))
990 andres@anarazel.de 292 : 0 : _bt_finish_split(rel, heaprel, buf, stack);
293 : : else
4291 heikki.linnakangas@i 294 : 0 : _bt_relbuf(rel, buf);
295 : :
296 : : /* re-acquire the lock in the right mode, and re-check */
920 pg@bowt.ie 297 : 0 : buf = _bt_getbuf(rel, blkno, access);
4291 heikki.linnakangas@i 298 : 0 : continue;
299 : : }
300 : :
2463 pg@bowt.ie 301 [ + - + + ]:CBC 4795509 : if (P_IGNORE(opaque) || _bt_compare(rel, key, page, P_HIKEY) >= cmpval)
302 : : {
303 : : /* step right one page */
4291 heikki.linnakangas@i 304 : 838 : buf = _bt_relandgetbuf(rel, buf, opaque->btpo_next, access);
305 : 838 : continue;
306 : : }
307 : : else
308 : : break;
309 : : }
310 : :
8333 tgl@sss.pgh.pa.us 311 [ - + ]: 20558928 : if (P_IGNORE(opaque))
6560 tgl@sss.pgh.pa.us 312 [ # # ]:UBC 0 : elog(ERROR, "fell off the end of index \"%s\"",
313 : : RelationGetRelationName(rel));
314 : :
9968 bruce@momjian.us 315 :CBC 20558928 : return buf;
316 : : }
317 : :
318 : : /*
319 : : * _bt_binsrch() -- Do a binary search for a key on a particular page.
320 : : *
321 : : * On an internal (non-leaf) page, _bt_binsrch() returns the OffsetNumber
322 : : * of the last key < given scankey, or last key <= given scankey if nextkey
323 : : * is true. (Since _bt_compare treats the first data key of such a page as
324 : : * minus infinity, there will be at least one key < scankey, so the result
325 : : * always points at one of the keys on the page.)
326 : : *
327 : : * On a leaf page, _bt_binsrch() returns the final result of the initial
328 : : * positioning process that started with _bt_first's call to _bt_search.
329 : : * We're returning a non-pivot tuple offset, so things are a little different.
330 : : * It is possible that we'll return an offset that's either past the last
331 : : * non-pivot slot, or (in the case of a backward scan) before the first slot.
332 : : *
333 : : * This procedure is not responsible for walking right, it just examines
334 : : * the given page. _bt_binsrch() has no lock or refcount side effects
335 : : * on the buffer.
336 : : */
337 : : static OffsetNumber
10752 scrappy@hub.org 338 : 16172896 : _bt_binsrch(Relation rel,
339 : : BTScanInsert key,
340 : : Buffer buf)
341 : : {
342 : : Page page;
343 : : BTPageOpaque opaque;
344 : : OffsetNumber low,
345 : : high;
346 : : int32 result,
347 : : cmpval;
348 : :
3527 kgrittn@postgresql.o 349 : 16172896 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 350 : 16172896 : opaque = BTPageGetOpaque(page);
351 : :
352 : : /* Requesting nextkey semantics while using scantid seems nonsensical */
2290 pg@bowt.ie 353 [ + + - + ]: 16172896 : Assert(!key->nextkey || key->scantid == NULL);
354 : : /* scantid-set callers must use _bt_binsrch_insert() on leaf pages */
355 [ + + - + ]: 16172896 : Assert(!P_ISLEAF(opaque) || key->scantid == NULL);
356 : :
9279 tgl@sss.pgh.pa.us 357 [ + + ]: 16172896 : low = P_FIRSTDATAKEY(opaque);
10327 bruce@momjian.us 358 : 16172896 : high = PageGetMaxOffsetNumber(page);
359 : :
360 : : /*
361 : : * If there are no keys on the page, return the first available slot. Note
362 : : * this covers two cases: the page is really empty (no keys), or it
363 : : * contains only a high key. The latter case is possible after vacuuming.
364 : : * This can never happen on an internal page, however, since they are
365 : : * never empty (an internal page must have at least one child).
366 : : */
2463 pg@bowt.ie 367 [ + + ]: 16172896 : if (unlikely(high < low))
9968 bruce@momjian.us 368 : 5242 : return low;
369 : :
370 : : /*
371 : : * Binary search to find the first key on the page >= scan key, or first
372 : : * key > scankey when nextkey is true.
373 : : *
374 : : * For nextkey=false (cmpval=1), the loop invariant is: all slots before
375 : : * 'low' are < scan key, all slots at or after 'high' are >= scan key.
376 : : *
377 : : * For nextkey=true (cmpval=0), the loop invariant is: all slots before
378 : : * 'low' are <= scan key, all slots at or after 'high' are > scan key.
379 : : *
380 : : * We can fall out when high == low.
381 : : */
9650 tgl@sss.pgh.pa.us 382 : 16167654 : high++; /* establish the loop invariant for high */
383 : :
2463 pg@bowt.ie 384 : 16167654 : cmpval = key->nextkey ? 0 : 1; /* select comparison value */
385 : :
9650 tgl@sss.pgh.pa.us 386 [ + + ]: 105500752 : while (high > low)
387 : : {
9379 bruce@momjian.us 388 : 89333098 : OffsetNumber mid = low + ((high - low) / 2);
389 : :
390 : : /* We have low <= mid < high, so mid points at a real slot */
391 : :
2463 pg@bowt.ie 392 : 89333098 : result = _bt_compare(rel, key, page, mid);
393 : :
8031 tgl@sss.pgh.pa.us 394 [ + + ]: 89333098 : if (result >= cmpval)
9650 395 : 56808111 : low = mid + 1;
396 : : else
397 : 32524987 : high = mid;
398 : : }
399 : :
400 : : /*
401 : : * At this point we have high == low.
402 : : *
403 : : * On a leaf page we always return the first non-pivot tuple >= scan key
404 : : * (resp. > scan key) for forward scan callers. For backward scans, it's
405 : : * always the _last_ non-pivot tuple < scan key (resp. <= scan key).
406 : : */
9279 407 [ + + ]: 16167654 : if (P_ISLEAF(opaque))
408 : : {
409 : : /*
410 : : * In the backward scan case we're supposed to locate the last
411 : : * matching tuple on the leaf level -- not the first matching tuple
412 : : * (the last tuple will be the first one returned by the scan).
413 : : *
414 : : * At this point we've located the first non-pivot tuple immediately
415 : : * after the last matching tuple (which might just be maxoff + 1).
416 : : * Compensate by stepping back.
417 : : */
739 pg@bowt.ie 418 [ + + ]: 7051492 : if (key->backward)
419 : 30001 : return OffsetNumberPrev(low);
420 : :
9650 tgl@sss.pgh.pa.us 421 : 7021491 : return low;
422 : : }
423 : :
424 : : /*
425 : : * On a non-leaf page, return the last key < scan key (resp. <= scan key).
426 : : * There must be one if _bt_compare() is playing by the rules.
427 : : *
428 : : * _bt_compare() will seldom see any exactly-matching pivot tuples, since
429 : : * a truncated -inf heap TID is usually enough to prevent it altogether.
430 : : * Even omitted scan key entries are treated as > truncated attributes.
431 : : *
432 : : * However, during backward scans _bt_compare() interprets omitted scan
433 : : * key attributes as == corresponding truncated -inf attributes instead.
434 : : * This works just like < would work here. Under this scheme, < strategy
435 : : * backward scans will always directly descend to the correct leaf page.
436 : : * In particular, they will never incur an "extra" leaf page access with a
437 : : * scan key that happens to contain the same prefix of values as some
438 : : * pivot tuple's untruncated prefix. VACUUM relies on this guarantee when
439 : : * it uses a leaf page high key to "re-find" a page undergoing deletion.
440 : : */
9279 441 [ + + - + ]: 9116162 : Assert(low > P_FIRSTDATAKEY(opaque));
442 : :
9650 443 : 9116162 : return OffsetNumberPrev(low);
444 : : }
445 : :
446 : : /*
447 : : *
448 : : * _bt_binsrch_insert() -- Cacheable, incremental leaf page binary search.
449 : : *
450 : : * Like _bt_binsrch(), but with support for caching the binary search
451 : : * bounds. Only used during insertion, and only on the leaf page that it
452 : : * looks like caller will insert tuple on. Exclusive-locked and pinned
453 : : * leaf page is contained within insertstate.
454 : : *
455 : : * Caches the bounds fields in insertstate so that a subsequent call can
456 : : * reuse the low and strict high bounds of original binary search. Callers
457 : : * that use these fields directly must be prepared for the case where low
458 : : * and/or stricthigh are not on the same page (one or both exceed maxoff
459 : : * for the page). The case where there are no items on the page (high <
460 : : * low) makes bounds invalid.
461 : : *
462 : : * Caller is responsible for invalidating bounds when it modifies the page
463 : : * before calling here a second time, and for dealing with posting list
464 : : * tuple matches (callers can use insertstate's postingoff field to
465 : : * determine which existing heap TID will need to be replaced by a posting
466 : : * list split).
467 : : */
468 : : OffsetNumber
2463 pg@bowt.ie 469 : 6664009 : _bt_binsrch_insert(Relation rel, BTInsertState insertstate)
470 : : {
471 : 6664009 : BTScanInsert key = insertstate->itup_key;
472 : : Page page;
473 : : BTPageOpaque opaque;
474 : : OffsetNumber low,
475 : : high,
476 : : stricthigh;
477 : : int32 result,
478 : : cmpval;
479 : :
480 : 6664009 : page = BufferGetPage(insertstate->buf);
1355 michael@paquier.xyz 481 : 6664009 : opaque = BTPageGetOpaque(page);
482 : :
2463 pg@bowt.ie 483 [ - + ]: 6664009 : Assert(P_ISLEAF(opaque));
484 [ - + ]: 6664009 : Assert(!key->nextkey);
2120 485 [ - + ]: 6664009 : Assert(insertstate->postingoff == 0);
486 : :
2463 487 [ + + ]: 6664009 : if (!insertstate->bounds_valid)
488 : : {
489 : : /* Start new binary search */
490 [ + + ]: 3970839 : low = P_FIRSTDATAKEY(opaque);
491 : 3970839 : high = PageGetMaxOffsetNumber(page);
492 : : }
493 : : else
494 : : {
495 : : /* Restore result of previous binary search against same page */
496 : 2693170 : low = insertstate->low;
497 : 2693170 : high = insertstate->stricthigh;
498 : : }
499 : :
500 : : /* If there are no keys on the page, return the first available slot */
501 [ + + ]: 6664009 : if (unlikely(high < low))
502 : : {
503 : : /* Caller can't reuse bounds */
504 : 11995 : insertstate->low = InvalidOffsetNumber;
505 : 11995 : insertstate->stricthigh = InvalidOffsetNumber;
506 : 11995 : insertstate->bounds_valid = false;
507 : 11995 : return low;
508 : : }
509 : :
510 : : /*
511 : : * Binary search to find the first key on the page >= scan key. (nextkey
512 : : * is always false when inserting).
513 : : *
514 : : * The loop invariant is: all slots before 'low' are < scan key, all slots
515 : : * at or after 'high' are >= scan key. 'stricthigh' is > scan key, and is
516 : : * maintained to save additional search effort for caller.
517 : : *
518 : : * We can fall out when high == low.
519 : : */
520 [ + + ]: 6652014 : if (!insertstate->bounds_valid)
521 : 3958844 : high++; /* establish the loop invariant for high */
522 : 6652014 : stricthigh = high; /* high initially strictly higher */
523 : :
524 : 6652014 : cmpval = 1; /* !nextkey comparison value */
525 : :
526 [ + + ]: 35689205 : while (high > low)
527 : : {
528 : 29037191 : OffsetNumber mid = low + ((high - low) / 2);
529 : :
530 : : /* We have low <= mid < high, so mid points at a real slot */
531 : :
532 : 29037191 : result = _bt_compare(rel, key, page, mid);
533 : :
534 [ + + ]: 29037191 : if (result >= cmpval)
535 : 22032688 : low = mid + 1;
536 : : else
537 : : {
538 : 7004503 : high = mid;
539 [ + + ]: 7004503 : if (result != 0)
540 : 6438153 : stricthigh = high;
541 : : }
542 : :
543 : : /*
544 : : * If tuple at offset located by binary search is a posting list whose
545 : : * TID range overlaps with caller's scantid, perform posting list
546 : : * binary search to set postingoff for caller. Caller must split the
547 : : * posting list when postingoff is set. This should happen
548 : : * infrequently.
549 : : */
2120 550 [ + + + + : 29037191 : if (unlikely(result == 0 && key->scantid != NULL))
+ + ]
551 : : {
552 : : /*
553 : : * postingoff should never be set more than once per leaf page
554 : : * binary search. That would mean that there are duplicate table
555 : : * TIDs in the index, which is never okay. Check for that here.
556 : : */
1511 557 [ - + ]: 217089 : if (insertstate->postingoff != 0)
1511 pg@bowt.ie 558 [ # # ]:UBC 0 : ereport(ERROR,
559 : : (errcode(ERRCODE_INDEX_CORRUPTED),
560 : : errmsg_internal("table tid from new index tuple (%u,%u) cannot find insert offset between offsets %u and %u of block %u in index \"%s\"",
561 : : ItemPointerGetBlockNumber(key->scantid),
562 : : ItemPointerGetOffsetNumber(key->scantid),
563 : : low, stricthigh,
564 : : BufferGetBlockNumber(insertstate->buf),
565 : : RelationGetRelationName(rel))));
566 : :
2120 pg@bowt.ie 567 :CBC 217089 : insertstate->postingoff = _bt_binsrch_posting(key, page, mid);
568 : : }
569 : : }
570 : :
571 : : /*
572 : : * On a leaf page, a binary search always returns the first key >= scan
573 : : * key (at least in !nextkey case), which could be the last slot + 1. This
574 : : * is also the lower bound of cached search.
575 : : *
576 : : * stricthigh may also be the last slot + 1, which prevents caller from
577 : : * using bounds directly, but is still useful to us if we're called a
578 : : * second time with cached bounds (cached low will be < stricthigh when
579 : : * that happens).
580 : : */
2463 581 : 6652014 : insertstate->low = low;
582 : 6652014 : insertstate->stricthigh = stricthigh;
583 : 6652014 : insertstate->bounds_valid = true;
584 : :
585 : 6652014 : return low;
586 : : }
587 : :
588 : : /*----------
589 : : * _bt_binsrch_posting() -- posting list binary search.
590 : : *
591 : : * Helper routine for _bt_binsrch_insert().
592 : : *
593 : : * Returns offset into posting list where caller's scantid belongs.
594 : : *----------
595 : : */
596 : : static int
2120 597 : 217089 : _bt_binsrch_posting(BTScanInsert key, Page page, OffsetNumber offnum)
598 : : {
599 : : IndexTuple itup;
600 : : ItemId itemid;
601 : : int low,
602 : : high,
603 : : mid,
604 : : res;
605 : :
606 : : /*
607 : : * If this isn't a posting tuple, then the index must be corrupt (if it is
608 : : * an ordinary non-pivot tuple then there must be an existing tuple with a
609 : : * heap TID that equals inserter's new heap TID/scantid). Defensively
610 : : * check that tuple is a posting list tuple whose posting list range
611 : : * includes caller's scantid.
612 : : *
613 : : * (This is also needed because contrib/amcheck's rootdescend option needs
614 : : * to be able to relocate a non-pivot tuple using _bt_binsrch_insert().)
615 : : */
616 : 217089 : itemid = PageGetItemId(page, offnum);
617 : 217089 : itup = (IndexTuple) PageGetItem(page, itemid);
618 [ + + ]: 217089 : if (!BTreeTupleIsPosting(itup))
619 : 201098 : return 0;
620 : :
621 [ + - - + ]: 15991 : Assert(key->heapkeyspace && key->allequalimage);
622 : :
623 : : /*
624 : : * In the event that posting list tuple has LP_DEAD bit set, indicate this
625 : : * to _bt_binsrch_insert() caller by returning -1, a sentinel value. A
626 : : * second call to _bt_binsrch_insert() can take place when its caller has
627 : : * removed the dead item.
628 : : */
629 [ + + ]: 15991 : if (ItemIdIsDead(itemid))
630 : 3 : return -1;
631 : :
632 : : /* "high" is past end of posting list for loop invariant */
633 : 15988 : low = 0;
634 : 15988 : high = BTreeTupleGetNPosting(itup);
635 [ - + ]: 15988 : Assert(high >= 2);
636 : :
637 [ + + ]: 128293 : while (high > low)
638 : : {
639 : 112305 : mid = low + ((high - low) / 2);
640 : 112305 : res = ItemPointerCompare(key->scantid,
2120 pg@bowt.ie 641 :GIC 112305 : BTreeTupleGetPostingN(itup, mid));
642 : :
2120 pg@bowt.ie 643 [ + + ]:CBC 112305 : if (res > 0)
644 : 58356 : low = mid + 1;
645 [ + - ]: 53949 : else if (res < 0)
646 : 53949 : high = mid;
647 : : else
2120 pg@bowt.ie 648 :UBC 0 : return mid;
649 : : }
650 : :
651 : : /* Exact match not found */
2120 pg@bowt.ie 652 :CBC 15988 : return low;
653 : : }
654 : :
655 : : /*----------
656 : : * _bt_compare() -- Compare insertion-type scankey to tuple on a page.
657 : : *
658 : : * page/offnum: location of btree item to be compared to.
659 : : *
660 : : * This routine returns:
661 : : * <0 if scankey < tuple at offnum;
662 : : * 0 if scankey == tuple at offnum;
663 : : * >0 if scankey > tuple at offnum.
664 : : *
665 : : * NULLs in the keys are treated as sortable values. Therefore
666 : : * "equality" does not necessarily mean that the item should be returned
667 : : * to the caller as a matching key. Similarly, an insertion scankey
668 : : * with its scantid set is treated as equal to a posting tuple whose TID
669 : : * range overlaps with their scantid. There generally won't be a
670 : : * matching TID in the posting tuple, which caller must handle
671 : : * themselves (e.g., by splitting the posting list tuple).
672 : : *
673 : : * CRUCIAL NOTE: on a non-leaf page, the first data key is assumed to be
674 : : * "minus infinity": this routine will always claim it is less than the
675 : : * scankey. The actual key value stored is explicitly truncated to 0
676 : : * attributes (explicitly minus infinity) with version 3+ indexes, but
677 : : * that isn't relied upon. This allows us to implement the Lehman and
678 : : * Yao convention that the first down-link pointer is before the first
679 : : * key. See backend/access/nbtree/README for details.
680 : : *----------
681 : : */
682 : : int32
10752 scrappy@hub.org 683 : 134157108 : _bt_compare(Relation rel,
684 : : BTScanInsert key,
685 : : Page page,
686 : : OffsetNumber offnum)
687 : : {
9279 tgl@sss.pgh.pa.us 688 : 134157108 : TupleDesc itupdesc = RelationGetDescr(rel);
1355 michael@paquier.xyz 689 : 134157108 : BTPageOpaque opaque = BTPageGetOpaque(page);
690 : : IndexTuple itup;
691 : : ItemPointer heapTid;
692 : : ScanKey scankey;
693 : : int ncmpkey;
694 : : int ntupatts;
695 : : int32 result;
696 : :
2463 pg@bowt.ie 697 [ - + ]: 134157108 : Assert(_bt_check_natts(rel, key->heapkeyspace, page, offnum));
698 [ - + ]: 134157108 : Assert(key->keysz <= IndexRelationGetNumberOfKeyAttributes(rel));
699 [ - + - - ]: 134157108 : Assert(key->heapkeyspace || key->scantid == NULL);
700 : :
701 : : /*
702 : : * Force result ">" if target item is first data item on an internal page
703 : : * --- see NOTE above.
704 : : */
9035 bruce@momjian.us 705 [ + + + + : 134157108 : if (!P_ISLEAF(opaque) && offnum == P_FIRSTDATAKEY(opaque))
+ + ]
9968 706 : 1568048 : return 1;
707 : :
7265 tgl@sss.pgh.pa.us 708 : 132589060 : itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
2463 pg@bowt.ie 709 [ + + ]: 132589060 : ntupatts = BTreeTupleGetNAtts(itup, rel);
710 : :
711 : : /*
712 : : * The scan key is set up with the attribute number associated with each
713 : : * term in the key. It is important that, if the index is multi-key, the
714 : : * scan contain the first k key attributes, and that they be in order. If
715 : : * you think about how multi-key ordering works, you'll understand why
716 : : * this is.
717 : : *
718 : : * We don't test for violation of this condition here, however. The
719 : : * initial setup for the index scan had better have gotten it right (see
720 : : * _bt_first).
721 : : */
722 : :
723 : 132589060 : ncmpkey = Min(ntupatts, key->keysz);
724 [ - + - - ]: 132589060 : Assert(key->heapkeyspace || ncmpkey == key->keysz);
2120 725 [ + + - + ]: 132589060 : Assert(!BTreeTupleIsPosting(itup) || key->allequalimage);
2463 726 : 132589060 : scankey = key->scankeys;
727 [ + + ]: 166901127 : for (int i = 1; i <= ncmpkey; i++)
728 : : {
729 : : Datum datum;
730 : : bool isNull;
731 : :
8070 tgl@sss.pgh.pa.us 732 : 155547229 : datum = index_getattr(itup, scankey->sk_attno, itupdesc, &isNull);
733 : :
3100 734 [ + + ]: 155547229 : if (scankey->sk_flags & SK_ISNULL) /* key is NULL */
735 : : {
9279 736 [ + + ]: 288105 : if (isNull)
9331 737 : 78692 : result = 0; /* NULL "=" NULL */
6916 738 [ + + ]: 209413 : else if (scankey->sk_flags & SK_BT_NULLS_FIRST)
739 : 312 : result = -1; /* NULL "<" NOT_NULL */
740 : : else
9331 741 : 209101 : result = 1; /* NULL ">" NOT_NULL */
742 : : }
9279 743 [ + + ]: 155259124 : else if (isNull) /* key is NOT_NULL and item is NULL */
744 : : {
6916 745 [ - + ]: 174 : if (scankey->sk_flags & SK_BT_NULLS_FIRST)
6916 tgl@sss.pgh.pa.us 746 :UBC 0 : result = 1; /* NOT_NULL ">" NULL */
747 : : else
6916 tgl@sss.pgh.pa.us 748 :CBC 174 : result = -1; /* NOT_NULL "<" NULL */
749 : : }
750 : : else
751 : : {
752 : : /*
753 : : * The sk_func needs to be passed the index value as left arg and
754 : : * the sk_argument as right arg (they might be of different
755 : : * types). Since it is convenient for callers to think of
756 : : * _bt_compare as comparing the scankey to the index item, we have
757 : : * to flip the sign of the comparison result. (Unless it's a DESC
758 : : * column, in which case we *don't* flip the sign.)
759 : : */
5362 760 : 155258950 : result = DatumGetInt32(FunctionCall2Coll(&scankey->sk_func,
761 : : scankey->sk_collation,
762 : : datum,
763 : : scankey->sk_argument));
764 : :
6916 765 [ + + ]: 155258950 : if (!(scankey->sk_flags & SK_BT_DESC))
2629 766 [ + + ]: 155258917 : INVERT_COMPARE_RESULT(result);
767 : : }
768 : :
769 : : /* if the keys are unequal, return the difference */
10327 bruce@momjian.us 770 [ + + ]: 155547229 : if (result != 0)
9968 771 : 121235162 : return result;
772 : :
8070 tgl@sss.pgh.pa.us 773 : 34312067 : scankey++;
774 : : }
775 : :
776 : : /*
777 : : * All non-truncated attributes (other than heap TID) were found to be
778 : : * equal. Treat truncated attributes as minus infinity when scankey has a
779 : : * key attribute value that would otherwise be compared directly.
780 : : *
781 : : * Note: it doesn't matter if ntupatts includes non-key attributes;
782 : : * scankey won't, so explicitly excluding non-key attributes isn't
783 : : * necessary.
784 : : */
2463 pg@bowt.ie 785 [ + + ]: 11353898 : if (key->keysz > ntupatts)
786 : 105953 : return 1;
787 : :
788 : : /*
789 : : * Use the heap TID attribute and scantid to try to break the tie. The
790 : : * rules are the same as any other key attribute -- only the
791 : : * representation differs.
792 : : */
793 : 11247945 : heapTid = BTreeTupleGetHeapTID(itup);
794 [ + + ]: 11247945 : if (key->scantid == NULL)
795 : : {
796 : : /*
797 : : * Forward scans have a scankey that is considered greater than a
798 : : * truncated pivot tuple if and when the scankey has equal values for
799 : : * attributes up to and including the least significant untruncated
800 : : * attribute in tuple. Even attributes that were omitted from the
801 : : * scan key are considered greater than -inf truncated attributes.
802 : : * (See _bt_binsrch for an explanation of our backward scan behavior.)
803 : : *
804 : : * For example, if an index has the minimum two attributes (single
805 : : * user key attribute, plus heap TID attribute), and a page's high key
806 : : * is ('foo', -inf), and scankey is ('foo', <omitted>), the search
807 : : * will not descend to the page to the left. The search will descend
808 : : * right instead. The truncated attribute in pivot tuple means that
809 : : * all non-pivot tuples on the page to the left are strictly < 'foo',
810 : : * so it isn't necessary to descend left. In other words, search
811 : : * doesn't have to descend left because it isn't interested in a match
812 : : * that has a heap TID value of -inf.
813 : : *
814 : : * Note: the heap TID part of the test ensures that scankey is being
815 : : * compared to a pivot tuple with one or more truncated -inf key
816 : : * attributes. The heap TID attribute is the last key attribute in
817 : : * every index, of course, but other than that it isn't special.
818 : : */
739 819 [ + + + + : 8951293 : if (!key->backward && key->keysz == ntupatts && heapTid == NULL &&
+ + ]
820 [ + - ]: 4622 : key->heapkeyspace)
2463 821 : 4622 : return 1;
822 : :
823 : : /* All provided scankey arguments found to be equal */
824 : 8946671 : return 0;
825 : : }
826 : :
827 : : /*
828 : : * Treat truncated heap TID as minus infinity, since scankey has a key
829 : : * attribute value (scantid) that would otherwise be compared directly
830 : : */
831 [ - + ]: 2296652 : Assert(key->keysz == IndexRelationGetNumberOfKeyAttributes(rel));
832 [ + + ]: 2296652 : if (heapTid == NULL)
833 : 1983 : return 1;
834 : :
835 : : /*
836 : : * Scankey must be treated as equal to a posting list tuple if its scantid
837 : : * value falls within the range of the posting list. In all other cases
838 : : * there can only be a single heap TID value, which is compared directly
839 : : * with scantid.
840 : : */
841 [ - + ]: 2294669 : Assert(ntupatts >= IndexRelationGetNumberOfKeyAttributes(rel));
2120 842 : 2294669 : result = ItemPointerCompare(key->scantid, heapTid);
843 [ + + + + ]: 2294669 : if (result <= 0 || !BTreeTupleIsPosting(itup))
844 : 2205376 : return result;
845 : : else
846 : : {
847 : 89293 : result = ItemPointerCompare(key->scantid,
2120 pg@bowt.ie 848 :GIC 89293 : BTreeTupleGetMaxHeapTID(itup));
2120 pg@bowt.ie 849 [ + + ]:CBC 89293 : if (result > 0)
850 : 73302 : return 1;
851 : : }
852 : :
853 : 15991 : return 0;
854 : : }
855 : :
856 : : /*
857 : : * _bt_first() -- Find the first item in a scan.
858 : : *
859 : : * We need to be clever about the direction of scan, the search
860 : : * conditions, and the tree ordering. We find the first item (or,
861 : : * if backwards scan, the last item) in the tree that satisfies the
862 : : * qualifications in the scan key. On success exit, data about the
863 : : * matching tuple(s) on the page has been loaded into so->currPos. We'll
864 : : * drop all locks and hold onto a pin on page's buffer, except during
865 : : * so->dropPin scans, when we drop both the lock and the pin.
866 : : * _bt_returnitem sets the next item to return to scan on success exit.
867 : : *
868 : : * If there are no matching items in the index, we return false, with no
869 : : * pins or locks held. so->currPos will remain invalid.
870 : : *
871 : : * Note that scan->keyData[], and the so->keyData[] scankey built from it,
872 : : * are both search-type scankeys (see nbtree/README for more about this).
873 : : * Within this routine, we build a temporary insertion-type scankey to use
874 : : * in locating the scan start position.
875 : : */
876 : : bool
10752 scrappy@hub.org 877 : 7363095 : _bt_first(IndexScanDesc scan, ScanDirection dir)
878 : : {
8607 tgl@sss.pgh.pa.us 879 : 7363095 : Relation rel = scan->indexRelation;
880 : 7363095 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
881 : : BTStack stack;
882 : : OffsetNumber offnum;
883 : : BTScanInsertData inskey;
884 : : ScanKey startKeys[INDEX_MAX_KEYS];
885 : : ScanKeyData notnullkey;
739 pg@bowt.ie 886 : 7363095 : int keysz = 0;
153 pg@bowt.ie 887 :GNC 7363095 : StrategyNumber strat_total = InvalidStrategy;
343 pg@bowt.ie 888 :CBC 7363095 : BlockNumber blkno = InvalidBlockNumber,
889 : : lastcurrblkno;
890 : :
3919 kgrittn@postgresql.o 891 [ + - - + : 7363095 : Assert(!BTScanPosIsValid(so->currPos));
- + ]
892 : :
893 : : /*
894 : : * Examine the scan keys and eliminate any redundant keys; also mark the
895 : : * keys that must be matched to continue the scan.
896 : : */
8070 tgl@sss.pgh.pa.us 897 : 7363095 : _bt_preprocess_keys(scan);
898 : :
899 : : /*
900 : : * Quit now if _bt_preprocess_keys() discovered that the scan keys can
901 : : * never be satisfied (eg, x == 1 AND x > 2).
902 : : */
9035 bruce@momjian.us 903 [ + + ]: 7363095 : if (!so->qual_ok)
904 : : {
343 pg@bowt.ie 905 [ - + ]: 1049 : Assert(!so->needPrimScan);
1916 akapila@postgresql.o 906 : 1049 : _bt_parallel_done(scan);
8611 tgl@sss.pgh.pa.us 907 : 1049 : return false;
908 : : }
909 : :
910 : : /*
911 : : * If this is a parallel scan, we must seize the scan. _bt_readfirstpage
912 : : * will likely release the parallel scan later on.
913 : : */
343 pg@bowt.ie 914 [ + + ]: 7362046 : if (scan->parallel_scan != NULL &&
915 [ + + ]: 223 : !_bt_parallel_seize(scan, &blkno, &lastcurrblkno, true))
916 : 103 : return false;
917 : :
918 : : /*
919 : : * Initialize the scan's arrays (if any) for the current scan direction
920 : : * (except when they were already set to later values as part of
921 : : * scheduling the primitive index scan that is now underway)
922 : : */
923 [ + + + + ]: 7361943 : if (so->numArrayKeys && !so->needPrimScan)
924 : 35694 : _bt_start_array_keys(scan, dir);
925 : :
926 [ + + ]: 7361943 : if (blkno != InvalidBlockNumber)
927 : : {
928 : : /*
929 : : * We anticipated calling _bt_search, but another worker bet us to it.
930 : : * _bt_readnextpage releases the scan for us (not _bt_readfirstpage).
931 : : */
932 [ - + ]: 58 : Assert(scan->parallel_scan != NULL);
933 [ - + ]: 58 : Assert(!so->needPrimScan);
403 934 [ - + ]: 58 : Assert(blkno != P_NONE);
935 : :
343 936 [ - + ]: 58 : if (!_bt_readnextpage(scan, blkno, lastcurrblkno, dir, true))
343 pg@bowt.ie 937 :LBC (1) : return false;
938 : :
343 pg@bowt.ie 939 :CBC 58 : _bt_returnitem(scan, so);
940 : 58 : return true;
941 : : }
942 : :
943 : : /*
944 : : * Count an indexscan for stats, now that we know that we'll call
945 : : * _bt_search/_bt_endpoint below
946 : : */
452 947 [ + + + + : 7361885 : pgstat_count_index_scan(rel);
+ + ]
280 948 [ + + ]: 7361885 : if (scan->instrument)
949 : 402470 : scan->instrument->nsearches++;
950 : :
951 : : /*----------
952 : : * Examine the scan keys to discover where we need to start the scan.
953 : : * The selected scan keys (at most one per index column) are remembered by
954 : : * storing their addresses into the local startKeys[] array. The final
955 : : * startKeys[] entry's strategy is set in strat_total. (Actually, there
956 : : * are a couple of cases where we force a less/more restrictive strategy.)
957 : : *
958 : : * We must use the key that was marked required (in the direction opposite
959 : : * our own scan's) during preprocessing. Each index attribute can only
960 : : * have one such required key. In general, the keys that we use to find
961 : : * an initial position when scanning forwards are the same keys that end
962 : : * the scan on the leaf level when scanning backwards (and vice-versa).
963 : : *
964 : : * When the scan keys include cross-type operators, _bt_preprocess_keys
965 : : * may not be able to eliminate redundant keys; in such cases it will
966 : : * arbitrarily pick a usable key for each attribute (and scan direction),
967 : : * ensuring that there is no more than one key required in each direction.
968 : : * We stop considering further keys once we reach the first nonrequired
969 : : * key (which must come after all required keys), so this can't affect us.
970 : : *
971 : : * The required keys that we use as starting boundaries have to be =, >,
972 : : * or >= keys for a forward scan or =, <, <= keys for a backwards scan.
973 : : * We can use keys for multiple attributes so long as the prior attributes
974 : : * had only =, >= (resp. =, <=) keys. These rules are very similar to the
975 : : * rules that preprocessing used to determine which keys to mark required.
976 : : * We cannot always use every required key as a positioning key, though.
977 : : * Skip arrays necessitate independently applying our own rules here.
978 : : * Skip arrays are always generally considered = array keys, but we'll
979 : : * nevertheless treat them as inequalities at certain points of the scan.
980 : : * When that happens, it _might_ have implications for the number of
981 : : * required keys that we can safely use for initial positioning purposes.
982 : : *
983 : : * For example, a forward scan with a skip array on its leading attribute
984 : : * (with no low_compare/high_compare) will have at least two required scan
985 : : * keys, but we won't use any of them as boundary keys during the scan's
986 : : * initial call here. Our positioning key during the first call here can
987 : : * be thought of as representing "> -infinity". Similarly, if such a skip
988 : : * array's low_compare is "a > 'foo'", then we position using "a > 'foo'"
989 : : * during the scan's initial call here; a lower-order key such as "b = 42"
990 : : * can't be used until the "a" array advances beyond MINVAL/low_compare.
991 : : *
992 : : * On the other hand, if such a skip array's low_compare was "a >= 'foo'",
993 : : * then we _can_ use "a >= 'foo' AND b = 42" during the initial call here.
994 : : * A subsequent call here might have us use "a = 'fop' AND b = 42". Note
995 : : * that we treat = and >= as equivalent when scanning forwards (just as we
996 : : * treat = and <= as equivalent when scanning backwards). We effectively
997 : : * do the same thing (though with a distinct "a" element/value) each time.
998 : : *
999 : : * All keys (with the exception of SK_SEARCHNULL keys and SK_BT_SKIP
1000 : : * array keys whose array is "null_elem=true") imply a NOT NULL qualifier.
1001 : : * If the index stores nulls at the end of the index we'll be starting
1002 : : * from, and we have no boundary key for the column (which means the key
1003 : : * we deduced NOT NULL from is an inequality key that constrains the other
1004 : : * end of the index), then we cons up an explicit SK_SEARCHNOTNULL key to
1005 : : * use as a boundary key. If we didn't do this, we might find ourselves
1006 : : * traversing a lot of null entries at the start of the scan.
1007 : : *
1008 : : * In this loop, row-comparison keys are treated the same as keys on their
1009 : : * first (leftmost) columns. We'll add all lower-order columns of the row
1010 : : * comparison that were marked required during preprocessing below.
1011 : : *
1012 : : * _bt_advance_array_keys needs to know exactly how we'll reposition the
1013 : : * scan (should it opt to schedule another primitive index scan). It is
1014 : : * critical that primscans only be scheduled when they'll definitely make
1015 : : * some useful progress. _bt_advance_array_keys does this by calling
1016 : : * _bt_checkkeys routines that report whether a tuple is past the end of
1017 : : * matches for the scan's keys (given the scan's current array elements).
1018 : : * If the page's final tuple is "after the end of matches" for a scan that
1019 : : * uses the *opposite* scan direction, then it must follow that it's also
1020 : : * "before the start of matches" for the actual current scan direction.
1021 : : * It is therefore essential that all of our initial positioning rules are
1022 : : * symmetric with _bt_checkkeys's corresponding continuescan=false rule.
1023 : : * If you update anything here, _bt_checkkeys/_bt_advance_array_keys might
1024 : : * need to be kept in sync.
1025 : : *----------
1026 : : */
9275 tgl@sss.pgh.pa.us 1027 [ + + ]: 7361885 : if (so->numberOfKeys > 0)
1028 : : {
1029 : : AttrNumber curattr;
1030 : : ScanKey bkey;
1031 : : ScanKey impliesNN;
1032 : : ScanKey cur;
1033 : :
1034 : : /*
1035 : : * bkey will be set to the key that preprocessing left behind as the
1036 : : * boundary key for this attribute, in this scan direction (if any)
1037 : : */
403 pg@bowt.ie 1038 : 7355333 : cur = so->keyData;
8070 tgl@sss.pgh.pa.us 1039 : 7355333 : curattr = 1;
167 pg@bowt.ie 1040 : 7355333 : bkey = NULL;
1041 : : /* Also remember any scankey that implies a NOT NULL constraint */
5158 tgl@sss.pgh.pa.us 1042 : 7355333 : impliesNN = NULL;
1043 : :
1044 : : /*
1045 : : * Loop iterates from 0 to numberOfKeys inclusive; we use the last
1046 : : * pass to handle after-last-key processing. Actual exit from the
1047 : : * loop is at one of the "break" statements below.
1048 : : */
403 pg@bowt.ie 1049 : 19218608 : for (int i = 0;; cur++, i++)
1050 : : {
8070 tgl@sss.pgh.pa.us 1051 [ + + + + ]: 19218608 : if (i >= so->numberOfKeys || cur->sk_attno != curattr)
1052 : : {
1053 : : /* Done looking for the curattr boundary key */
167 pg@bowt.ie 1054 [ + + + - : 11862366 : Assert(bkey == NULL ||
- + ]
1055 : : (bkey->sk_attno == curattr &&
1056 : : (bkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD))));
1057 [ + + + - : 11862366 : Assert(impliesNN == NULL ||
- + ]
1058 : : (impliesNN->sk_attno == curattr &&
1059 : : (impliesNN->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD))));
1060 : :
1061 : : /*
1062 : : * If this is a scan key for a skip array whose current
1063 : : * element is MINVAL, choose low_compare (when scanning
1064 : : * backwards it'll be MAXVAL, and we'll choose high_compare).
1065 : : *
1066 : : * Note: if the array's low_compare key makes 'bkey' NULL,
1067 : : * then we behave as if the array's first element is -inf,
1068 : : * except when !array->null_elem implies a usable NOT NULL
1069 : : * constraint.
1070 : : */
1071 [ + + ]: 11862366 : if (bkey != NULL &&
1072 [ + + ]: 11825227 : (bkey->sk_flags & (SK_BT_MINVAL | SK_BT_MAXVAL)))
1073 : : {
1074 : 1882 : int ikey = bkey - so->keyData;
1075 : 1882 : ScanKey skipequalitykey = bkey;
256 1076 : 1882 : BTArrayKeyInfo *array = NULL;
1077 : :
1078 [ + - ]: 1938 : for (int arridx = 0; arridx < so->numArrayKeys; arridx++)
1079 : : {
1080 : 1938 : array = &so->arrayKeys[arridx];
1081 [ + + ]: 1938 : if (array->scan_key == ikey)
1082 : 1882 : break;
1083 : : }
1084 : :
1085 [ + + ]: 1882 : if (ScanDirectionIsForward(dir))
1086 : : {
1087 [ - + ]: 1873 : Assert(!(skipequalitykey->sk_flags & SK_BT_MAXVAL));
167 1088 : 1873 : bkey = array->low_compare;
1089 : : }
1090 : : else
1091 : : {
256 1092 [ - + ]: 9 : Assert(!(skipequalitykey->sk_flags & SK_BT_MINVAL));
167 1093 : 9 : bkey = array->high_compare;
1094 : : }
1095 : :
1096 [ + + - + ]: 1882 : Assert(bkey == NULL ||
1097 : : bkey->sk_attno == skipequalitykey->sk_attno);
1098 : :
256 1099 [ + + ]: 1882 : if (!array->null_elem)
1100 : 86 : impliesNN = skipequalitykey;
1101 : : else
167 1102 [ + - - + ]: 1796 : Assert(bkey == NULL && impliesNN == NULL);
1103 : : }
1104 : :
1105 : : /*
1106 : : * If we didn't find a usable boundary key, see if we can
1107 : : * deduce a NOT NULL key
1108 : : */
1109 [ + + + + : 11899535 : if (bkey == NULL && impliesNN != NULL &&
+ + ]
5158 tgl@sss.pgh.pa.us 1110 [ + + ]: 37169 : ((impliesNN->sk_flags & SK_BT_NULLS_FIRST) ?
1111 : : ScanDirectionIsForward(dir) :
1112 : : ScanDirectionIsBackward(dir)))
1113 : : {
1114 : : /* Final startKeys[] entry will be deduced NOT NULL key */
153 pg@bowt.ie 1115 :GNC 15 : bkey = ¬nullkey;
167 pg@bowt.ie 1116 [ + + ]:CBC 15 : ScanKeyEntryInitialize(bkey,
1117 : : (SK_SEARCHNOTNULL | SK_ISNULL |
5158 tgl@sss.pgh.pa.us 1118 : 15 : (impliesNN->sk_flags &
1119 : : (SK_BT_DESC | SK_BT_NULLS_FIRST))),
1120 : : curattr,
1121 : : ScanDirectionIsForward(dir) ?
1122 : : BTGreaterStrategyNumber : BTLessStrategyNumber,
1123 : : InvalidOid,
1124 : : InvalidOid,
1125 : : InvalidOid,
1126 : : (Datum) 0);
1127 : : }
1128 : :
1129 : : /*
1130 : : * If preprocessing didn't leave a usable boundary key, quit;
1131 : : * else save the boundary key pointer in startKeys[]
1132 : : */
167 pg@bowt.ie 1133 [ + + ]: 11862366 : if (bkey == NULL)
8070 tgl@sss.pgh.pa.us 1134 : 38950 : break;
167 pg@bowt.ie 1135 : 11823416 : startKeys[keysz++] = bkey;
1136 : :
1137 : : /*
1138 : : * We can only consider adding more boundary keys when the one
1139 : : * that we just chose to add uses either the = or >= strategy
1140 : : * (during backwards scans we can only do so when the key that
1141 : : * we just added to startKeys[] uses the = or <= strategy)
1142 : : */
1143 : 11823416 : strat_total = bkey->sk_strategy;
407 1144 [ + + + + ]: 11823416 : if (strat_total == BTGreaterStrategyNumber ||
1145 : : strat_total == BTLessStrategyNumber)
1146 : : break;
1147 : :
1148 : : /*
1149 : : * If the key that we just added to startKeys[] is a skip
1150 : : * array = key whose current element is marked NEXT or PRIOR,
1151 : : * make strat_total > or < (and stop adding boundary keys).
1152 : : * This can only happen with opclasses that lack skip support.
1153 : : */
167 1154 [ + + ]: 11117141 : if (bkey->sk_flags & (SK_BT_NEXT | SK_BT_PRIOR))
1155 : : {
1156 [ - + ]: 6 : Assert(bkey->sk_flags & SK_BT_SKIP);
256 1157 [ - + ]: 6 : Assert(strat_total == BTEqualStrategyNumber);
1158 : :
1159 [ + + ]: 6 : if (ScanDirectionIsForward(dir))
1160 : : {
167 1161 [ - + ]: 3 : Assert(!(bkey->sk_flags & SK_BT_PRIOR));
256 1162 : 3 : strat_total = BTGreaterStrategyNumber;
1163 : : }
1164 : : else
1165 : : {
167 1166 [ - + ]: 3 : Assert(!(bkey->sk_flags & SK_BT_NEXT));
256 1167 : 3 : strat_total = BTLessStrategyNumber;
1168 : : }
1169 : :
1170 : : /*
1171 : : * We're done. We'll never find an exact = match for a
1172 : : * NEXT or PRIOR sentinel sk_argument value. There's no
1173 : : * sense in trying to add more keys to startKeys[].
1174 : : */
1175 : 6 : break;
1176 : : }
1177 : :
1178 : : /*
1179 : : * Done if that was the last scan key output by preprocessing.
1180 : : * Also done if we've now examined all keys marked required.
1181 : : */
7491 tgl@sss.pgh.pa.us 1182 [ + + ]: 11117135 : if (i >= so->numberOfKeys ||
167 pg@bowt.ie 1183 [ + + ]: 4507036 : !(cur->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)))
1184 : : break;
1185 : :
1186 : : /*
1187 : : * Reset for next attr.
1188 : : */
1189 [ - + ]: 4507033 : Assert(cur->sk_attno == curattr + 1);
8070 tgl@sss.pgh.pa.us 1190 : 4507033 : curattr = cur->sk_attno;
167 pg@bowt.ie 1191 : 4507033 : bkey = NULL;
5158 tgl@sss.pgh.pa.us 1192 : 4507033 : impliesNN = NULL;
1193 : : }
1194 : :
1195 : : /*
1196 : : * If we've located the starting boundary key for curattr, we have
1197 : : * no interest in curattr's other required key
1198 : : */
167 pg@bowt.ie 1199 [ + + ]: 11863275 : if (bkey != NULL)
1200 : 897 : continue;
1201 : :
1202 : : /*
1203 : : * Is this key the starting boundary key for curattr?
1204 : : *
1205 : : * If not, does it imply a NOT NULL constraint? (Because
1206 : : * SK_SEARCHNULL keys are always assigned BTEqualStrategyNumber,
1207 : : * *any* inequality key works for that; we need not test.)
1208 : : */
8070 tgl@sss.pgh.pa.us 1209 [ + + + - ]: 11862378 : switch (cur->sk_strategy)
1210 : : {
1211 : 67028 : case BTLessStrategyNumber:
1212 : : case BTLessEqualStrategyNumber:
167 pg@bowt.ie 1213 [ + + ]: 67028 : if (ScanDirectionIsBackward(dir))
1214 : 29898 : bkey = cur;
1215 [ + - ]: 37130 : else if (impliesNN == NULL)
1216 : 37130 : impliesNN = cur;
8070 tgl@sss.pgh.pa.us 1217 : 67028 : break;
1218 : 11113907 : case BTEqualStrategyNumber:
167 pg@bowt.ie 1219 : 11113907 : bkey = cur;
8070 tgl@sss.pgh.pa.us 1220 : 11113907 : break;
1221 : 681443 : case BTGreaterEqualStrategyNumber:
1222 : : case BTGreaterStrategyNumber:
167 pg@bowt.ie 1223 [ + + ]: 681443 : if (ScanDirectionIsForward(dir))
1224 : 681422 : bkey = cur;
1225 [ + - ]: 21 : else if (impliesNN == NULL)
1226 : 21 : impliesNN = cur;
9744 bruce@momjian.us 1227 : 681443 : break;
1228 : : }
1229 : : }
1230 : : }
1231 : :
1232 : : /*
1233 : : * If we found no usable boundary keys, we have to start from one end of
1234 : : * the tree. Walk down that edge to the first or last key, and scan from
1235 : : * there.
1236 : : *
1237 : : * Note: calls _bt_readfirstpage for us, which releases the parallel scan.
1238 : : */
739 pg@bowt.ie 1239 [ + + ]: 7361885 : if (keysz == 0)
407 1240 : 45135 : return _bt_endpoint(scan, dir);
1241 : :
1242 : : /*
1243 : : * We want to start the scan somewhere within the index. Set up an
1244 : : * insertion scankey we can use to search for the boundary point we
1245 : : * identified above. The insertion scankey is built using the keys
1246 : : * identified by startKeys[]. (Remaining insertion scankey fields are
1247 : : * initialized after initial-positioning scan keys are finalized.)
1248 : : */
739 1249 [ - + ]: 7316750 : Assert(keysz <= INDEX_MAX_KEYS);
403 1250 [ + + ]: 19140142 : for (int i = 0; i < keysz; i++)
1251 : : {
167 1252 : 11823416 : ScanKey bkey = startKeys[i];
1253 : :
1254 [ - + ]: 11823416 : Assert(bkey->sk_attno == i + 1);
1255 : :
1256 [ + + ]: 11823416 : if (bkey->sk_flags & SK_ROW_HEADER)
1257 : : {
1258 : : /*
1259 : : * Row comparison header: look to the first row member instead
1260 : : */
1261 : 24 : ScanKey subkey = (ScanKey) DatumGetPointer(bkey->sk_argument);
1262 : 24 : bool loosen_strat = false,
1263 : 24 : tighten_strat = false;
1264 : :
1265 : : /*
1266 : : * Cannot be a NULL in the first row member: _bt_preprocess_keys
1267 : : * would've marked the qual as unsatisfiable, preventing us from
1268 : : * ever getting this far
1269 : : */
6916 tgl@sss.pgh.pa.us 1270 [ - + ]: 24 : Assert(subkey->sk_flags & SK_ROW_MEMBER);
167 pg@bowt.ie 1271 [ - + ]: 24 : Assert(subkey->sk_attno == bkey->sk_attno);
343 1272 [ - + ]: 24 : Assert(!(subkey->sk_flags & SK_ISNULL));
1273 : :
1274 : : /*
1275 : : * This is either a > or >= key (during backwards scans it is
1276 : : * either < or <=) that was marked required during preprocessing.
1277 : : * Later so->keyData[] keys can't have been marked required, so
1278 : : * our row compare header key must be the final startKeys[] entry.
1279 : : */
167 1280 [ - + ]: 24 : Assert(subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD));
44 1281 [ - + ]: 24 : Assert(subkey->sk_strategy == bkey->sk_strategy);
1282 [ - + ]: 24 : Assert(subkey->sk_strategy == strat_total);
167 1283 [ - + ]: 24 : Assert(i == keysz - 1);
1284 : :
1285 : : /*
1286 : : * The member scankeys are already in insertion format (ie, they
1287 : : * have sk_func = 3-way-comparison function)
1288 : : */
2463 1289 : 24 : memcpy(inskey.scankeys + i, subkey, sizeof(ScanKeyData));
1290 : :
1291 : : /*
1292 : : * Now look to later row compare members.
1293 : : *
1294 : : * If there's an "index attribute gap" between two row compare
1295 : : * members, the second member won't have been marked required, and
1296 : : * so can't be used as a starting boundary key here. The part of
1297 : : * the row comparison that we do still use has to be treated as a
1298 : : * ">=" or "<=" condition. For example, a qual "(a, c) > (1, 42)"
1299 : : * with an omitted intervening index attribute "b" will use an
1300 : : * insertion scan key "a >= 1". Even the first "a = 1" tuple on
1301 : : * the leaf level might satisfy the row compare qual.
1302 : : *
1303 : : * We're able to use a _more_ restrictive strategy when we reach a
1304 : : * NULL row compare member, since they're always unsatisfiable.
1305 : : * For example, a qual "(a, b, c) >= (1, NULL, 77)" will use an
1306 : : * insertion scan key "a > 1". All tuples where "a = 1" cannot
1307 : : * possibly satisfy the row compare qual, so this is safe.
1308 : : */
167 1309 [ - + ]: 24 : Assert(!(subkey->sk_flags & SK_ROW_END));
1310 : : for (;;)
1311 : : {
1312 : 24 : subkey++;
1313 [ - + ]: 24 : Assert(subkey->sk_flags & SK_ROW_MEMBER);
1314 : :
1315 [ + + ]: 24 : if (subkey->sk_flags & SK_ISNULL)
1316 : : {
1317 : : /*
1318 : : * NULL member key, can only use earlier keys.
1319 : : *
1320 : : * We deliberately avoid checking if this key is marked
1321 : : * required. All earlier keys are required, and this key
1322 : : * is unsatisfiable either way, so we can't miss anything.
1323 : : */
1324 : 6 : tighten_strat = true;
1325 : 6 : break;
1326 : : }
1327 : :
1328 [ + + ]: 18 : if (!(subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)))
1329 : : {
1330 : : /* nonrequired member key, can only use earlier keys */
1331 : 6 : loosen_strat = true;
1332 : 6 : break;
1333 : : }
1334 : :
1335 [ - + ]: 12 : Assert(subkey->sk_attno == keysz + 1);
1336 [ - + ]: 12 : Assert(subkey->sk_strategy == bkey->sk_strategy);
1337 [ - + ]: 12 : Assert(keysz < INDEX_MAX_KEYS);
1338 : :
44 1339 : 12 : memcpy(inskey.scankeys + keysz, subkey, sizeof(ScanKeyData));
167 1340 : 12 : keysz++;
1341 : :
1342 [ + - ]: 12 : if (subkey->sk_flags & SK_ROW_END)
1343 : 12 : break;
1344 : : }
1345 [ + + - + ]: 24 : Assert(!(loosen_strat && tighten_strat));
1346 [ + + ]: 24 : if (loosen_strat)
1347 : : {
1348 : : /* Use less restrictive strategy (and fewer member keys) */
1349 [ + + - ]: 6 : switch (strat_total)
1350 : : {
1351 : 3 : case BTLessStrategyNumber:
1352 : 3 : strat_total = BTLessEqualStrategyNumber;
1353 : 3 : break;
1354 : 3 : case BTGreaterStrategyNumber:
1355 : 3 : strat_total = BTGreaterEqualStrategyNumber;
1356 : 3 : break;
1357 : : }
1358 : : }
1359 [ + + ]: 24 : if (tighten_strat)
1360 : : {
1361 : : /* Use more restrictive strategy (and fewer member keys) */
1362 [ + + - ]: 6 : switch (strat_total)
1363 : : {
1364 : 3 : case BTLessEqualStrategyNumber:
1365 : 3 : strat_total = BTLessStrategyNumber;
1366 : 3 : break;
1367 : 3 : case BTGreaterEqualStrategyNumber:
1368 : 3 : strat_total = BTGreaterStrategyNumber;
1369 : 3 : break;
1370 : : }
1371 : : }
1372 : :
1373 : : /* Done (row compare header key is always last startKeys[] key) */
1374 : 24 : break;
1375 : : }
1376 : :
1377 : : /*
1378 : : * Ordinary comparison key/search-style key.
1379 : : *
1380 : : * Transform the search-style scan key to an insertion scan key by
1381 : : * replacing the sk_func with the appropriate btree 3-way-comparison
1382 : : * function.
1383 : : *
1384 : : * If scankey operator is not a cross-type comparison, we can use the
1385 : : * cached comparison function; otherwise gotta look it up in the
1386 : : * catalogs. (That can't lead to infinite recursion, since no
1387 : : * indexscan initiated by syscache lookup will use cross-data-type
1388 : : * operators.)
1389 : : *
1390 : : * We support the convention that sk_subtype == InvalidOid means the
1391 : : * opclass input type; this hack simplifies life for ScanKeyInit().
1392 : : */
1393 [ + + ]: 11823392 : if (bkey->sk_subtype == rel->rd_opcintype[i] ||
1394 [ + + ]: 11397707 : bkey->sk_subtype == InvalidOid)
1395 : 11817933 : {
1396 : : FmgrInfo *procinfo;
1397 : :
1398 : 11817933 : procinfo = index_getprocinfo(rel, bkey->sk_attno, BTORDER_PROC);
1399 : 11817933 : ScanKeyEntryInitializeWithInfo(inskey.scankeys + i,
1400 : : bkey->sk_flags,
1401 : 11817933 : bkey->sk_attno,
1402 : : InvalidStrategy,
1403 : : bkey->sk_subtype,
1404 : : bkey->sk_collation,
1405 : : procinfo,
1406 : : bkey->sk_argument);
1407 : : }
1408 : : else
1409 : : {
1410 : : RegProcedure cmp_proc;
1411 : :
1412 : 5459 : cmp_proc = get_opfamily_proc(rel->rd_opfamily[i],
1413 : 5459 : rel->rd_opcintype[i],
1414 : : bkey->sk_subtype, BTORDER_PROC);
1415 [ - + ]: 5459 : if (!RegProcedureIsValid(cmp_proc))
167 pg@bowt.ie 1416 [ # # ]:UBC 0 : elog(ERROR, "missing support function %d(%u,%u) for attribute %d of index \"%s\"",
1417 : : BTORDER_PROC, rel->rd_opcintype[i], bkey->sk_subtype,
1418 : : bkey->sk_attno, RelationGetRelationName(rel));
167 pg@bowt.ie 1419 :CBC 5459 : ScanKeyEntryInitialize(inskey.scankeys + i,
1420 : : bkey->sk_flags,
1421 : 5459 : bkey->sk_attno,
1422 : : InvalidStrategy,
1423 : : bkey->sk_subtype,
1424 : : bkey->sk_collation,
1425 : : cmp_proc,
1426 : : bkey->sk_argument);
1427 : : }
1428 : : }
1429 : :
1430 : : /*----------
1431 : : * Examine the selected initial-positioning strategy to determine exactly
1432 : : * where we need to start the scan, and set flag variables to control the
1433 : : * initial descent by _bt_search (and our _bt_binsrch call for the leaf
1434 : : * page _bt_search returns).
1435 : : *----------
1436 : : */
739 1437 : 7316750 : _bt_metaversion(rel, &inskey.heapkeyspace, &inskey.allequalimage);
1438 : 7316750 : inskey.anynullkeys = false; /* unused */
1439 : 7316750 : inskey.scantid = NULL;
1440 : 7316750 : inskey.keysz = keysz;
8031 tgl@sss.pgh.pa.us 1441 [ + + + + : 7316750 : switch (strat_total)
+ - ]
1442 : : {
1443 : 29901 : case BTLessStrategyNumber:
1444 : :
739 pg@bowt.ie 1445 : 29901 : inskey.nextkey = false;
1446 : 29901 : inskey.backward = true;
8031 tgl@sss.pgh.pa.us 1447 : 29901 : break;
1448 : :
1449 : 9 : case BTLessEqualStrategyNumber:
1450 : :
739 pg@bowt.ie 1451 : 9 : inskey.nextkey = true;
1452 : 9 : inskey.backward = true;
8031 tgl@sss.pgh.pa.us 1453 : 9 : break;
1454 : :
1455 : 6605406 : case BTEqualStrategyNumber:
1456 : :
1457 : : /*
1458 : : * If a backward scan was specified, need to start with last equal
1459 : : * item not first one.
1460 : : */
1461 [ + + ]: 6605406 : if (ScanDirectionIsBackward(dir))
1462 : : {
1463 : : /*
1464 : : * This is the same as the <= strategy
1465 : : */
739 pg@bowt.ie 1466 : 100 : inskey.nextkey = true;
1467 : 100 : inskey.backward = true;
1468 : : }
1469 : : else
1470 : : {
1471 : : /*
1472 : : * This is the same as the >= strategy
1473 : : */
1474 : 6605306 : inskey.nextkey = false;
1475 : 6605306 : inskey.backward = false;
1476 : : }
8031 tgl@sss.pgh.pa.us 1477 : 6605406 : break;
1478 : :
1479 : 5054 : case BTGreaterEqualStrategyNumber:
1480 : :
1481 : : /*
1482 : : * Find first item >= scankey
1483 : : */
739 pg@bowt.ie 1484 : 5054 : inskey.nextkey = false;
1485 : 5054 : inskey.backward = false;
8031 tgl@sss.pgh.pa.us 1486 : 5054 : break;
1487 : :
1488 : 676380 : case BTGreaterStrategyNumber:
1489 : :
1490 : : /*
1491 : : * Find first item > scankey
1492 : : */
739 pg@bowt.ie 1493 : 676380 : inskey.nextkey = true;
1494 : 676380 : inskey.backward = false;
8031 tgl@sss.pgh.pa.us 1495 : 676380 : break;
1496 : :
8031 tgl@sss.pgh.pa.us 1497 :UBC 0 : default:
1498 : : /* can't get here, but keep compiler quiet */
1499 [ # # ]: 0 : elog(ERROR, "unrecognized strat_total: %d", (int) strat_total);
1500 : : return false;
1501 : : }
1502 : :
1503 : : /*
1504 : : * Use the manufactured insertion scan key to descend the tree and
1505 : : * position ourselves on the target leaf page.
1506 : : */
739 pg@bowt.ie 1507 [ - + ]:CBC 7316750 : Assert(ScanDirectionIsBackward(dir) == inskey.backward);
424 1508 : 7316750 : stack = _bt_search(rel, NULL, &inskey, &so->currPos.buf, BT_READ);
1509 : :
1510 : : /* don't need to keep the stack around... */
9279 tgl@sss.pgh.pa.us 1511 : 7316750 : _bt_freestack(stack);
1512 : :
424 pg@bowt.ie 1513 [ + + ]: 7316750 : if (!BufferIsValid(so->currPos.buf))
1514 : : {
167 1515 [ - + ]: 260016 : Assert(!so->needPrimScan);
1516 : :
1517 : : /*
1518 : : * We only get here if the index is completely empty. Lock relation
1519 : : * because nothing finer to lock exists. Without a buffer lock, it's
1520 : : * possible for another transaction to insert data between
1521 : : * _bt_search() and PredicateLockRelation(). We have to try again
1522 : : * after taking the relation-level predicate lock, to close a narrow
1523 : : * window where we wouldn't scan concurrently inserted tuples, but the
1524 : : * writer wouldn't see our predicate lock.
1525 : : */
897 tmunro@postgresql.or 1526 [ + + ]: 260016 : if (IsolationIsSerializable())
1527 : : {
1528 : 2831 : PredicateLockRelation(rel, scan->xs_snapshot);
424 pg@bowt.ie 1529 : 2831 : stack = _bt_search(rel, NULL, &inskey, &so->currPos.buf, BT_READ);
897 tmunro@postgresql.or 1530 : 2831 : _bt_freestack(stack);
1531 : : }
1532 : :
424 pg@bowt.ie 1533 [ + - ]: 260016 : if (!BufferIsValid(so->currPos.buf))
1534 : : {
897 tmunro@postgresql.or 1535 : 260016 : _bt_parallel_done(scan);
1536 : 260016 : return false;
1537 : : }
1538 : : }
1539 : :
1540 : : /* position to the precise item on the page */
424 pg@bowt.ie 1541 : 7056734 : offnum = _bt_binsrch(rel, &inskey, so->currPos.buf);
1542 : :
1543 : : /*
1544 : : * Now load data from the first page of the scan (usually the page
1545 : : * currently in so->currPos.buf).
1546 : : *
1547 : : * If inskey.nextkey = false and inskey.backward = false, offnum is
1548 : : * positioned at the first non-pivot tuple >= inskey.scankeys.
1549 : : *
1550 : : * If inskey.nextkey = false and inskey.backward = true, offnum is
1551 : : * positioned at the last non-pivot tuple < inskey.scankeys.
1552 : : *
1553 : : * If inskey.nextkey = true and inskey.backward = false, offnum is
1554 : : * positioned at the first non-pivot tuple > inskey.scankeys.
1555 : : *
1556 : : * If inskey.nextkey = true and inskey.backward = true, offnum is
1557 : : * positioned at the last non-pivot tuple <= inskey.scankeys.
1558 : : *
1559 : : * It's possible that _bt_binsrch returned an offnum that is out of bounds
1560 : : * for the page. For example, when inskey is both < the leaf page's high
1561 : : * key and > all of its non-pivot tuples, offnum will be "maxoff + 1".
1562 : : */
1563 [ + + ]: 7056734 : if (!_bt_readfirstpage(scan, offnum, dir))
1564 : 2073357 : return false;
1565 : :
398 1566 : 4983377 : _bt_returnitem(scan, so);
7163 tgl@sss.pgh.pa.us 1567 : 4983377 : return true;
1568 : : }
1569 : :
1570 : : /*
1571 : : * _bt_next() -- Get the next item in a scan.
1572 : : *
1573 : : * On entry, so->currPos describes the current page, which may be pinned
1574 : : * but is not locked, and so->currPos.itemIndex identifies which item was
1575 : : * previously returned.
1576 : : *
1577 : : * On success exit, so->currPos is updated as needed, and _bt_returnitem
1578 : : * sets the next item to return to the scan. so->currPos remains valid.
1579 : : *
1580 : : * On failure exit (no more tuples), we invalidate so->currPos. It'll
1581 : : * still be possible for the scan to return tuples by changing direction,
1582 : : * though we'll need to call _bt_first anew in that other direction.
1583 : : */
1584 : : bool
1585 : 9511319 : _bt_next(IndexScanDesc scan, ScanDirection dir)
1586 : : {
1587 : 9511319 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
1588 : :
407 pg@bowt.ie 1589 [ - + - - : 9511319 : Assert(BTScanPosIsValid(so->currPos));
- + ]
1590 : :
1591 : : /*
1592 : : * Advance to next tuple on current page; or if there's no more, try to
1593 : : * step to the next page with data.
1594 : : */
7163 tgl@sss.pgh.pa.us 1595 [ + + ]: 9511319 : if (ScanDirectionIsForward(dir))
1596 : : {
1597 [ + + ]: 9494936 : if (++so->currPos.itemIndex > so->currPos.lastItem)
1598 : : {
1599 [ + + ]: 1224018 : if (!_bt_steppage(scan, dir))
1600 : 1209354 : return false;
1601 : : }
1602 : : }
1603 : : else
1604 : : {
1605 [ + + ]: 16383 : if (--so->currPos.itemIndex < so->currPos.firstItem)
1606 : : {
1607 [ + + ]: 57 : if (!_bt_steppage(scan, dir))
8611 1608 : 46 : return false;
1609 : : }
1610 : : }
1611 : :
398 pg@bowt.ie 1612 : 8301919 : _bt_returnitem(scan, so);
7163 tgl@sss.pgh.pa.us 1613 : 8301919 : return true;
1614 : : }
1615 : :
1616 : : /*
1617 : : * Return the index item from so->currPos.items[so->currPos.itemIndex] to the
1618 : : * index scan by setting the relevant fields in caller's index scan descriptor
1619 : : */
1620 : : static inline void
398 pg@bowt.ie 1621 : 13325896 : _bt_returnitem(IndexScanDesc scan, BTScanOpaque so)
1622 : : {
1623 : 13325896 : BTScanPosItem *currItem = &so->currPos.items[so->currPos.itemIndex];
1624 : :
1625 : : /* Most recent _bt_readpage must have succeeded */
1626 [ - + - - : 13325896 : Assert(BTScanPosIsValid(so->currPos));
- + ]
1627 [ - + ]: 13325896 : Assert(so->currPos.itemIndex >= so->currPos.firstItem);
1628 [ - + ]: 13325896 : Assert(so->currPos.itemIndex <= so->currPos.lastItem);
1629 : :
1630 : : /* Return next item, per amgettuple contract */
1631 : 13325896 : scan->xs_heaptid = currItem->heapTid;
1632 [ + + ]: 13325896 : if (so->currTuples)
1633 : 2245676 : scan->xs_itup = (IndexTuple) (so->currTuples + currItem->tupleOffset);
1634 : 13325896 : }
1635 : :
1636 : : /*
1637 : : * _bt_steppage() -- Step to next page containing valid data for scan
1638 : : *
1639 : : * Wrapper on _bt_readnextpage that performs final steps for the current page.
1640 : : *
1641 : : * On entry, so->currPos must be valid. Its buffer will be pinned, though
1642 : : * never locked. (Actually, when so->dropPin there won't even be a pin held,
1643 : : * though so->currPos.currPage must still be set to a valid block number.)
1644 : : */
1645 : : static bool
7163 tgl@sss.pgh.pa.us 1646 : 3298367 : _bt_steppage(IndexScanDesc scan, ScanDirection dir)
1647 : : {
9279 1648 : 3298367 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
1649 : : BlockNumber blkno,
1650 : : lastcurrblkno;
1651 : :
3919 kgrittn@postgresql.o 1652 [ - + - - : 3298367 : Assert(BTScanPosIsValid(so->currPos));
- + ]
1653 : :
1654 : : /* Before leaving current page, deal with any killed items */
7163 tgl@sss.pgh.pa.us 1655 [ + + ]: 3298367 : if (so->numKilled > 0)
3919 kgrittn@postgresql.o 1656 : 42654 : _bt_killitems(scan);
1657 : :
1658 : : /*
1659 : : * Before we modify currPos, make a copy of the page data if there was a
1660 : : * mark position that needs it.
1661 : : */
7054 tgl@sss.pgh.pa.us 1662 [ + + ]: 3298367 : if (so->markItemIndex >= 0)
1663 : : {
1664 : : /* bump pin on current buffer for assignment to mark buffer */
3919 kgrittn@postgresql.o 1665 [ - + - - : 183 : if (BTScanPosIsPinned(so->currPos))
+ + ]
1666 : 174 : IncrBufferRefCount(so->currPos.buf);
7054 tgl@sss.pgh.pa.us 1667 : 183 : memcpy(&so->markPos, &so->currPos,
1668 : : offsetof(BTScanPosData, items[1]) +
1669 : 183 : so->currPos.lastItem * sizeof(BTScanPosItem));
5182 1670 [ + + ]: 183 : if (so->markTuples)
1671 : 174 : memcpy(so->markTuples, so->currTuples,
1672 : 174 : so->currPos.nextTupleOffset);
7054 1673 : 183 : so->markPos.itemIndex = so->markItemIndex;
1674 : 183 : so->markItemIndex = -1;
1675 : :
1676 : : /*
1677 : : * If we're just about to start the next primitive index scan
1678 : : * (possible with a scan that has arrays keys, and needs to skip to
1679 : : * continue in the current scan direction), moreLeft/moreRight only
1680 : : * indicate the end of the current primitive index scan. They must
1681 : : * never be taken to indicate that the top-level index scan has ended
1682 : : * (that would be wrong).
1683 : : *
1684 : : * We could handle this case by treating the current array keys as
1685 : : * markPos state. But depending on the current array state like this
1686 : : * would add complexity. Instead, we just unset markPos's copy of
1687 : : * moreRight or moreLeft (whichever might be affected), while making
1688 : : * btrestrpos reset the scan's arrays to their initial scan positions.
1689 : : * In effect, btrestrpos leaves advancing the arrays up to the first
1690 : : * _bt_readpage call (that takes place after it has restored markPos).
1691 : : */
619 pg@bowt.ie 1692 [ - + ]: 183 : if (so->needPrimScan)
1693 : : {
412 pg@bowt.ie 1694 [ # # ]:UBC 0 : if (ScanDirectionIsForward(so->currPos.dir))
619 1695 : 0 : so->markPos.moreRight = true;
1696 : : else
1697 : 0 : so->markPos.moreLeft = true;
1698 : : }
1699 : :
1700 : : /* mark/restore not supported by parallel scans */
424 pg@bowt.ie 1701 [ - + ]:CBC 183 : Assert(!scan->parallel_scan);
1702 : : }
1703 : :
1704 [ - + - - : 3298367 : BTScanPosUnpinIfPinned(so->currPos);
+ + ]
1705 : :
1706 : : /* Walk to the next page with data */
403 1707 [ + + ]: 3298367 : if (ScanDirectionIsForward(dir))
1708 : 3298295 : blkno = so->currPos.nextPage;
1709 : : else
1710 : 72 : blkno = so->currPos.prevPage;
1711 : 3298367 : lastcurrblkno = so->currPos.currPage;
1712 : :
1713 : : /*
1714 : : * Cancel primitive index scans that were scheduled when the call to
1715 : : * _bt_readpage for currPos happened to use the opposite direction to the
1716 : : * one that we're stepping in now. (It's okay to leave the scan's array
1717 : : * keys as-is, since the next _bt_readpage will advance them.)
1718 : : */
1719 [ + + ]: 3298367 : if (so->currPos.dir != dir)
1720 : 18 : so->needPrimScan = false;
1721 : :
1722 : 3298367 : return _bt_readnextpage(scan, blkno, lastcurrblkno, dir, false);
1723 : : }
1724 : :
1725 : : /*
1726 : : * _bt_readfirstpage() -- Read first page containing valid data for _bt_first
1727 : : *
1728 : : * _bt_first caller passes us an offnum returned by _bt_binsrch, which might
1729 : : * be an out of bounds offnum such as "maxoff + 1" in certain corner cases.
1730 : : * When we're passed an offnum past the end of the page, we might still manage
1731 : : * to stop the scan on this page by calling _bt_checkkeys against the high
1732 : : * key. See _bt_readpage for full details.
1733 : : *
1734 : : * On entry, so->currPos must be pinned and locked (so offnum stays valid).
1735 : : * Parallel scan callers must have seized the scan before calling here.
1736 : : *
1737 : : * On exit, we'll have updated so->currPos and retained locks and pins
1738 : : * according to the same rules as those laid out for _bt_readnextpage exit.
1739 : : * Like _bt_readnextpage, our return value indicates if there are any matching
1740 : : * records in the given direction.
1741 : : *
1742 : : * We always release the scan for a parallel scan caller, regardless of
1743 : : * success or failure; we'll call _bt_parallel_release as soon as possible.
1744 : : */
1745 : : static bool
424 1746 : 7098167 : _bt_readfirstpage(IndexScanDesc scan, OffsetNumber offnum, ScanDirection dir)
1747 : : {
1748 : 7098167 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
1749 : :
1750 : 7098167 : so->numKilled = 0; /* just paranoia */
1751 : 7098167 : so->markItemIndex = -1; /* ditto */
1752 : :
1753 : : /* Initialize so->currPos for the first page (page in so->currPos.buf) */
1754 [ + + ]: 7098167 : if (so->needPrimScan)
1755 : : {
1756 [ - + ]: 8791 : Assert(so->numArrayKeys);
1757 : :
1758 : 8791 : so->currPos.moreLeft = true;
1759 : 8791 : so->currPos.moreRight = true;
1760 : 8791 : so->needPrimScan = false;
1761 : : }
1762 [ + + ]: 7089376 : else if (ScanDirectionIsForward(dir))
1763 : : {
1764 : 7059351 : so->currPos.moreLeft = false;
3226 rhaas@postgresql.org 1765 : 7059351 : so->currPos.moreRight = true;
1766 : : }
1767 : : else
1768 : : {
424 pg@bowt.ie 1769 : 30025 : so->currPos.moreLeft = true;
1770 : 30025 : so->currPos.moreRight = false;
1771 : : }
1772 : :
1773 : : /*
1774 : : * Attempt to load matching tuples from the first page.
1775 : : *
1776 : : * Note that _bt_readpage will finish initializing the so->currPos fields.
1777 : : * _bt_readpage also releases parallel scan (even when it returns false).
1778 : : */
1779 [ + + ]: 7098167 : if (_bt_readpage(scan, dir, offnum, true))
1780 : : {
193 1781 : 5023875 : Relation rel = scan->indexRelation;
1782 : :
1783 : : /*
1784 : : * _bt_readpage succeeded. Drop the lock (and maybe the pin) on
1785 : : * so->currPos.buf in preparation for btgettuple returning tuples.
1786 : : */
424 1787 [ - + - - : 5023875 : Assert(BTScanPosIsPinned(so->currPos));
- + ]
193 1788 : 5023875 : _bt_drop_lock_and_maybe_pin(rel, so);
424 1789 : 5023875 : return true;
1790 : : }
1791 : :
1792 : : /* There's no actually-matching data on the page in so->currPos.buf */
1793 : 2074292 : _bt_unlockbuf(scan->indexRelation, so->currPos.buf);
1794 : :
1795 : : /* Call _bt_readnextpage using its _bt_steppage wrapper function */
1796 [ + + ]: 2074292 : if (!_bt_steppage(scan, dir))
1797 : 2074248 : return false;
1798 : :
1799 : : /* _bt_readpage for a later page (now in so->currPos) succeeded */
3226 rhaas@postgresql.org 1800 : 44 : return true;
1801 : : }
1802 : :
1803 : : /*
1804 : : * _bt_readnextpage() -- Read next page containing valid data for _bt_next
1805 : : *
1806 : : * Caller's blkno is the next interesting page's link, taken from either the
1807 : : * previously-saved right link or left link. lastcurrblkno is the page that
1808 : : * was current at the point where the blkno link was saved, which we use to
1809 : : * reason about concurrent page splits/page deletions during backwards scans.
1810 : : * In the common case where seized=false, blkno is either so->currPos.nextPage
1811 : : * or so->currPos.prevPage, and lastcurrblkno is so->currPos.currPage.
1812 : : *
1813 : : * On entry, so->currPos shouldn't be locked by caller. so->currPos.buf must
1814 : : * be InvalidBuffer/unpinned as needed by caller (note that lastcurrblkno
1815 : : * won't need to be read again in almost all cases). Parallel scan callers
1816 : : * that seized the scan before calling here should pass seized=true; such a
1817 : : * caller's blkno and lastcurrblkno arguments come from the seized scan.
1818 : : * seized=false callers just pass us the blkno/lastcurrblkno taken from their
1819 : : * so->currPos, which (along with so->currPos itself) can be used to end the
1820 : : * scan. A seized=false caller's blkno can never be assumed to be the page
1821 : : * that must be read next during a parallel scan, though. We must figure that
1822 : : * part out for ourselves by seizing the scan (the correct page to read might
1823 : : * already be beyond the seized=false caller's blkno during a parallel scan,
1824 : : * unless blkno/so->currPos.nextPage/so->currPos.prevPage is already P_NONE,
1825 : : * or unless so->currPos.moreRight/so->currPos.moreLeft is already unset).
1826 : : *
1827 : : * On success exit, so->currPos is updated to contain data from the next
1828 : : * interesting page, and we return true. We hold a pin on the buffer on
1829 : : * success exit (except during so->dropPin index scans, when we drop the pin
1830 : : * eagerly to avoid blocking VACUUM).
1831 : : *
1832 : : * If there are no more matching records in the given direction, we invalidate
1833 : : * so->currPos (while ensuring it retains no locks or pins), and return false.
1834 : : *
1835 : : * We always release the scan for a parallel scan caller, regardless of
1836 : : * success or failure; we'll call _bt_parallel_release as soon as possible.
1837 : : */
1838 : : static bool
424 pg@bowt.ie 1839 : 3298425 : _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno,
1840 : : BlockNumber lastcurrblkno, ScanDirection dir, bool seized)
1841 : : {
1842 : 3298425 : Relation rel = scan->indexRelation;
3226 rhaas@postgresql.org 1843 : 3298425 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
1844 : :
403 pg@bowt.ie 1845 [ + + - + ]: 3298425 : Assert(so->currPos.currPage == lastcurrblkno || seized);
284 1846 [ + + - + ]: 3298425 : Assert(!(blkno == P_NONE && seized));
424 1847 [ + + - + : 3298425 : Assert(!BTScanPosIsPinned(so->currPos));
- + ]
1848 : :
1849 : : /*
1850 : : * Remember that the scan already read lastcurrblkno, a page to the left
1851 : : * of blkno (or remember reading a page to the right, for backwards scans)
1852 : : */
3226 rhaas@postgresql.org 1853 [ + + ]: 3298425 : if (ScanDirectionIsForward(dir))
424 pg@bowt.ie 1854 : 3298353 : so->currPos.moreLeft = true;
1855 : : else
1856 : 72 : so->currPos.moreRight = true;
1857 : :
1858 : : for (;;)
10327 bruce@momjian.us 1859 : 1179 : {
1860 : : Page page;
1861 : : BTPageOpaque opaque;
1862 : :
424 pg@bowt.ie 1863 [ + + + + ]: 3299604 : if (blkno == P_NONE ||
1864 : : (ScanDirectionIsForward(dir) ?
1865 [ + + + + ]: 1114204 : !so->currPos.moreRight : !so->currPos.moreLeft))
1866 : : {
1867 : : /* most recent _bt_readpage call (for lastcurrblkno) ended scan */
403 1868 [ + - - + ]: 3283590 : Assert(so->currPos.currPage == lastcurrblkno && !seized);
492 1869 : 3283590 : BTScanPosInvalidate(so->currPos);
403 1870 : 3283590 : _bt_parallel_done(scan); /* iff !so->needPrimScan */
492 1871 : 3283590 : return false;
1872 : : }
1873 : :
412 1874 [ - + ]: 16014 : Assert(!so->needPrimScan);
1875 : :
1876 : : /* parallel scan must never actually visit so->currPos blkno */
403 1877 [ + + + + ]: 16014 : if (!seized && scan->parallel_scan != NULL &&
1878 [ + + ]: 606 : !_bt_parallel_seize(scan, &blkno, &lastcurrblkno, false))
1879 : : {
1880 : : /* whole scan is now done (or another primitive scan required) */
1881 : 58 : BTScanPosInvalidate(so->currPos);
1882 : 58 : return false;
1883 : : }
1884 : :
424 1885 [ + + ]: 15956 : if (ScanDirectionIsForward(dir))
1886 : : {
1887 : : /* read blkno, but check for interrupts first */
1888 [ - + ]: 15933 : CHECK_FOR_INTERRUPTS();
1889 : 15933 : so->currPos.buf = _bt_getbuf(rel, blkno, BT_READ);
1890 : : }
1891 : : else
1892 : : {
1893 : : /* read blkno, avoiding race (also checks for interrupts) */
1894 : 23 : so->currPos.buf = _bt_lock_and_validate_left(rel, &blkno,
1895 : : lastcurrblkno);
1896 [ - + ]: 23 : if (so->currPos.buf == InvalidBuffer)
1897 : : {
1898 : : /* must have been a concurrent deletion of leftmost page */
3919 kgrittn@postgresql.o 1899 :UBC 0 : BTScanPosInvalidate(so->currPos);
407 pg@bowt.ie 1900 : 0 : _bt_parallel_done(scan);
7163 tgl@sss.pgh.pa.us 1901 : 0 : return false;
1902 : : }
1903 : : }
1904 : :
424 pg@bowt.ie 1905 :CBC 15956 : page = BufferGetPage(so->currPos.buf);
1906 : 15956 : opaque = BTPageGetOpaque(page);
1907 : 15956 : lastcurrblkno = blkno;
1908 [ + - ]: 15956 : if (likely(!P_IGNORE(opaque)))
1909 : : {
1910 : : /* see if there are any matches on this page */
1911 [ + + ]: 15956 : if (ScanDirectionIsForward(dir))
1912 : : {
1913 : : /* note that this will clear moreRight if we can stop */
269 1914 [ + + + + ]: 15933 : if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque), seized))
424 1915 : 14763 : break;
1916 : 1170 : blkno = so->currPos.nextPage;
1917 : : }
1918 : : else
1919 : : {
1920 : : /* note that this will clear moreLeft if we can stop */
269 1921 [ + + ]: 23 : if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page), seized))
7163 tgl@sss.pgh.pa.us 1922 : 14 : break;
424 pg@bowt.ie 1923 : 9 : blkno = so->currPos.prevPage;
1924 : : }
1925 : : }
1926 : : else
1927 : : {
1928 : : /* _bt_readpage not called, so do all this for ourselves */
424 pg@bowt.ie 1929 [ # # ]:UBC 0 : if (ScanDirectionIsForward(dir))
1930 : 0 : blkno = opaque->btpo_next;
1931 : : else
1932 : 0 : blkno = opaque->btpo_prev;
3226 rhaas@postgresql.org 1933 [ # # ]: 0 : if (scan->parallel_scan != NULL)
424 pg@bowt.ie 1934 : 0 : _bt_parallel_release(scan, blkno, lastcurrblkno);
1935 : : }
1936 : :
1937 : : /* no matching tuples on this page */
424 pg@bowt.ie 1938 :CBC 1179 : _bt_relbuf(rel, so->currPos.buf);
403 1939 : 1179 : seized = false; /* released by _bt_readpage (or by us) */
1940 : : }
1941 : :
1942 : : /*
1943 : : * _bt_readpage succeeded. Drop the lock (and maybe the pin) on
1944 : : * so->currPos.buf in preparation for btgettuple returning tuples.
1945 : : */
424 1946 [ - + ]: 14777 : Assert(so->currPos.currPage == blkno);
1947 [ - + - - : 14777 : Assert(BTScanPosIsPinned(so->currPos));
- + ]
193 1948 : 14777 : _bt_drop_lock_and_maybe_pin(rel, so);
1949 : :
9968 bruce@momjian.us 1950 : 14777 : return true;
1951 : : }
1952 : :
1953 : : /*
1954 : : * _bt_lock_and_validate_left() -- lock caller's left sibling blkno,
1955 : : * recovering from concurrent page splits/page deletions when necessary
1956 : : *
1957 : : * Called during backwards scans, to deal with their unique concurrency rules.
1958 : : *
1959 : : * blkno points to the block number of the page that we expect to move the
1960 : : * scan to. We'll successfully move the scan there when we find that its
1961 : : * right sibling link still points to lastcurrblkno (the page we just read).
1962 : : * Otherwise, we have to figure out which page is the correct one for the scan
1963 : : * to now read the hard way, reasoning about concurrent splits and deletions.
1964 : : * See nbtree/README.
1965 : : *
1966 : : * On return, we have both a pin and a read lock on the returned page, whose
1967 : : * block number will be set in *blkno. Returns InvalidBuffer if there is no
1968 : : * page to the left (no lock or pin is held in that case).
1969 : : *
1970 : : * It is possible for the returned leaf page to be half-dead; caller must
1971 : : * check that condition and step left again when required.
1972 : : */
1973 : : static Buffer
424 pg@bowt.ie 1974 : 23 : _bt_lock_and_validate_left(Relation rel, BlockNumber *blkno,
1975 : : BlockNumber lastcurrblkno)
1976 : : {
1977 : 23 : BlockNumber origblkno = *blkno; /* detects circular links */
1978 : :
1979 : : for (;;)
8333 tgl@sss.pgh.pa.us 1980 :UBC 0 : {
1981 : : Buffer buf;
1982 : : Page page;
1983 : : BTPageOpaque opaque;
1984 : : int tries;
1985 : :
1986 : : /* check for interrupts while we're not holding any buffer lock */
6069 tgl@sss.pgh.pa.us 1987 [ - + ]:CBC 23 : CHECK_FOR_INTERRUPTS();
424 pg@bowt.ie 1988 : 23 : buf = _bt_getbuf(rel, *blkno, BT_READ);
3527 kgrittn@postgresql.o 1989 : 23 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 1990 : 23 : opaque = BTPageGetOpaque(page);
1991 : :
1992 : : /*
1993 : : * If this isn't the page we want, walk right till we find what we
1994 : : * want --- but go no more than four hops (an arbitrary limit). If we
1995 : : * don't find the correct page by then, the most likely bet is that
1996 : : * lastcurrblkno got deleted and isn't in the sibling chain at all
1997 : : * anymore, not that its left sibling got split more than four times.
1998 : : *
1999 : : * Note that it is correct to test P_ISDELETED not P_IGNORE here,
2000 : : * because half-dead pages are still in the sibling chain.
2001 : : */
8333 tgl@sss.pgh.pa.us 2002 : 23 : tries = 0;
2003 : : for (;;)
2004 : : {
424 pg@bowt.ie 2005 [ + - + - : 23 : if (likely(!P_ISDELETED(opaque) &&
+ - ]
2006 : : opaque->btpo_next == lastcurrblkno))
2007 : : {
2008 : : /* Found desired page, return it */
8333 tgl@sss.pgh.pa.us 2009 : 23 : return buf;
2010 : : }
8333 tgl@sss.pgh.pa.us 2011 [ # # # # ]:UBC 0 : if (P_RIGHTMOST(opaque) || ++tries > 4)
2012 : : break;
2013 : : /* step right */
424 pg@bowt.ie 2014 : 0 : *blkno = opaque->btpo_next;
2015 : 0 : buf = _bt_relandgetbuf(rel, buf, *blkno, BT_READ);
3527 kgrittn@postgresql.o 2016 : 0 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2017 : 0 : opaque = BTPageGetOpaque(page);
2018 : : }
2019 : :
2020 : : /*
2021 : : * Return to the original page (usually the page most recently read by
2022 : : * _bt_readpage, which is passed by caller as lastcurrblkno) to see
2023 : : * what's up with its prev sibling link
2024 : : */
424 pg@bowt.ie 2025 : 0 : buf = _bt_relandgetbuf(rel, buf, lastcurrblkno, BT_READ);
3527 kgrittn@postgresql.o 2026 : 0 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2027 : 0 : opaque = BTPageGetOpaque(page);
8333 tgl@sss.pgh.pa.us 2028 [ # # ]: 0 : if (P_ISDELETED(opaque))
2029 : : {
2030 : : /*
2031 : : * It was deleted. Move right to first nondeleted page (there
2032 : : * must be one); that is the page that has acquired the deleted
2033 : : * one's keyspace, so stepping left from it will take us where we
2034 : : * want to be.
2035 : : */
2036 : : for (;;)
2037 : : {
2038 [ # # ]: 0 : if (P_RIGHTMOST(opaque))
6560 2039 [ # # ]: 0 : elog(ERROR, "fell off the end of index \"%s\"",
2040 : : RelationGetRelationName(rel));
424 pg@bowt.ie 2041 : 0 : lastcurrblkno = opaque->btpo_next;
2042 : 0 : buf = _bt_relandgetbuf(rel, buf, lastcurrblkno, BT_READ);
3527 kgrittn@postgresql.o 2043 : 0 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2044 : 0 : opaque = BTPageGetOpaque(page);
8333 tgl@sss.pgh.pa.us 2045 [ # # ]: 0 : if (!P_ISDELETED(opaque))
2046 : 0 : break;
2047 : : }
2048 : : }
2049 : : else
2050 : : {
2051 : : /*
2052 : : * Original lastcurrblkno wasn't deleted; the explanation had
2053 : : * better be that the page to the left got split or deleted.
2054 : : * Without this check, we risk going into an infinite loop.
2055 : : */
424 pg@bowt.ie 2056 [ # # ]: 0 : if (opaque->btpo_prev == origblkno)
6560 tgl@sss.pgh.pa.us 2057 [ # # ]: 0 : elog(ERROR, "could not find left sibling of block %u in index \"%s\"",
2058 : : lastcurrblkno, RelationGetRelationName(rel));
2059 : : /* Okay to try again, since left sibling link changed */
2060 : : }
2061 : :
2062 : : /*
2063 : : * Original lastcurrblkno from caller was concurrently deleted (could
2064 : : * also have been a great many concurrent left sibling page splits).
2065 : : * Found a non-deleted page that should now act as our lastcurrblkno.
2066 : : */
424 pg@bowt.ie 2067 [ # # ]: 0 : if (P_LEFTMOST(opaque))
2068 : : {
2069 : : /* New lastcurrblkno has no left sibling (concurrently deleted) */
2070 : 0 : _bt_relbuf(rel, buf);
2071 : 0 : break;
2072 : : }
2073 : :
2074 : : /* Start from scratch with new lastcurrblkno's blkno/prev link */
2075 : 0 : *blkno = origblkno = opaque->btpo_prev;
2076 : 0 : _bt_relbuf(rel, buf);
2077 : : }
2078 : :
8333 tgl@sss.pgh.pa.us 2079 : 0 : return InvalidBuffer;
2080 : : }
2081 : :
2082 : : /*
2083 : : * _bt_get_endpoint() -- Find the first or last page on a given tree level
2084 : : *
2085 : : * If the index is empty, we will return InvalidBuffer; any other failure
2086 : : * condition causes ereport(). We will not return a dead page.
2087 : : *
2088 : : * The returned buffer is pinned and read-locked.
2089 : : */
2090 : : Buffer
830 tmunro@postgresql.or 2091 :CBC 45147 : _bt_get_endpoint(Relation rel, uint32 level, bool rightmost)
2092 : : {
2093 : : Buffer buf;
2094 : : Page page;
2095 : : BTPageOpaque opaque;
2096 : : OffsetNumber offnum;
2097 : : BlockNumber blkno;
2098 : : IndexTuple itup;
2099 : :
2100 : : /*
2101 : : * If we are looking for a leaf page, okay to descend from fast root;
2102 : : * otherwise better descend from true root. (There is no point in being
2103 : : * smarter about intermediate levels.)
2104 : : */
8334 tgl@sss.pgh.pa.us 2105 [ + + ]: 45147 : if (level == 0)
920 pg@bowt.ie 2106 : 45135 : buf = _bt_getroot(rel, NULL, BT_READ);
2107 : : else
2108 : 12 : buf = _bt_gettrueroot(rel);
2109 : :
8334 tgl@sss.pgh.pa.us 2110 [ + + ]: 45147 : if (!BufferIsValid(buf))
2111 : 3702 : return InvalidBuffer;
2112 : :
3527 kgrittn@postgresql.o 2113 : 41445 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2114 : 41445 : opaque = BTPageGetOpaque(page);
2115 : :
2116 : : for (;;)
2117 : : {
2118 : : /*
2119 : : * If we landed on a deleted page, step right to find a live page
2120 : : * (there must be one). Also, if we want the rightmost page, step
2121 : : * right if needed to get to it (this could happen if the page split
2122 : : * since we obtained a pointer to it).
2123 : : */
8333 tgl@sss.pgh.pa.us 2124 [ - + + + ]: 53357 : while (P_IGNORE(opaque) ||
8334 2125 [ - + ]: 33 : (rightmost && !P_RIGHTMOST(opaque)))
2126 : : {
8334 tgl@sss.pgh.pa.us 2127 :UBC 0 : blkno = opaque->btpo_next;
2128 [ # # ]: 0 : if (blkno == P_NONE)
6560 2129 [ # # ]: 0 : elog(ERROR, "fell off the end of index \"%s\"",
2130 : : RelationGetRelationName(rel));
7909 2131 : 0 : buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
3527 kgrittn@postgresql.o 2132 : 0 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2133 : 0 : opaque = BTPageGetOpaque(page);
2134 : : }
2135 : :
2136 : : /* Done? */
1756 pg@bowt.ie 2137 [ + + ]:CBC 53357 : if (opaque->btpo_level == level)
8334 tgl@sss.pgh.pa.us 2138 : 41445 : break;
1756 pg@bowt.ie 2139 [ - + ]: 11912 : if (opaque->btpo_level < level)
2329 peter@eisentraut.org 2140 [ # # ]:UBC 0 : ereport(ERROR,
2141 : : (errcode(ERRCODE_INDEX_CORRUPTED),
2142 : : errmsg_internal("btree level %u not found in index \"%s\"",
2143 : : level, RelationGetRelationName(rel))));
2144 : :
2145 : : /* Descend to leftmost or rightmost child page */
8334 tgl@sss.pgh.pa.us 2146 [ + + ]:CBC 11912 : if (rightmost)
2147 : 3 : offnum = PageGetMaxOffsetNumber(page);
2148 : : else
2149 [ + + ]: 11909 : offnum = P_FIRSTDATAKEY(opaque);
2150 : :
1 tgl@sss.pgh.pa.us 2151 [ + - - + ]:GNC 11912 : if (offnum < 1 || offnum > PageGetMaxOffsetNumber(page))
1 tgl@sss.pgh.pa.us 2152 [ # # ]:UNC 0 : elog(PANIC, "offnum out of range");
2153 : :
7265 tgl@sss.pgh.pa.us 2154 :CBC 11912 : itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
2192 pg@bowt.ie 2155 : 11912 : blkno = BTreeTupleGetDownLink(itup);
2156 : :
7909 tgl@sss.pgh.pa.us 2157 : 11912 : buf = _bt_relandgetbuf(rel, buf, blkno, BT_READ);
3527 kgrittn@postgresql.o 2158 : 11912 : page = BufferGetPage(buf);
1355 michael@paquier.xyz 2159 : 11912 : opaque = BTPageGetOpaque(page);
2160 : : }
2161 : :
8334 tgl@sss.pgh.pa.us 2162 : 41445 : return buf;
2163 : : }
2164 : :
2165 : : /*
2166 : : * _bt_endpoint() -- Find the first or last page in the index, and scan
2167 : : * from there to the first key satisfying all the quals.
2168 : : *
2169 : : * This is used by _bt_first() to set up a scan when we've determined
2170 : : * that the scan must start at the beginning or end of the index (for
2171 : : * a forward or backward scan respectively).
2172 : : *
2173 : : * Parallel scan callers must have seized the scan before calling here.
2174 : : * Exit conditions are the same as for _bt_first().
2175 : : */
2176 : : static bool
10752 scrappy@hub.org 2177 : 45135 : _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
2178 : : {
7163 tgl@sss.pgh.pa.us 2179 : 45135 : Relation rel = scan->indexRelation;
2180 : 45135 : BTScanOpaque so = (BTScanOpaque) scan->opaque;
2181 : : Page page;
2182 : : BTPageOpaque opaque;
2183 : : OffsetNumber start;
2184 : :
407 pg@bowt.ie 2185 [ + - - + : 45135 : Assert(!BTScanPosIsValid(so->currPos));
- + ]
343 2186 [ - + ]: 45135 : Assert(!so->needPrimScan);
2187 : :
2188 : : /*
2189 : : * Scan down to the leftmost or rightmost leaf page. This is a simplified
2190 : : * version of _bt_search().
2191 : : */
424 2192 : 45135 : so->currPos.buf = _bt_get_endpoint(rel, 0, ScanDirectionIsBackward(dir));
2193 : :
2194 [ + + ]: 45135 : if (!BufferIsValid(so->currPos.buf))
2195 : : {
2196 : : /*
2197 : : * Empty index. Lock the whole relation, as nothing finer to lock
2198 : : * exists.
2199 : : */
5298 heikki.linnakangas@i 2200 : 3702 : PredicateLockRelation(rel, scan->xs_snapshot);
407 pg@bowt.ie 2201 : 3702 : _bt_parallel_done(scan);
8611 tgl@sss.pgh.pa.us 2202 : 3702 : return false;
2203 : : }
2204 : :
424 pg@bowt.ie 2205 : 41433 : page = BufferGetPage(so->currPos.buf);
1355 michael@paquier.xyz 2206 : 41433 : opaque = BTPageGetOpaque(page);
8334 tgl@sss.pgh.pa.us 2207 [ - + ]: 41433 : Assert(P_ISLEAF(opaque));
2208 : :
10327 bruce@momjian.us 2209 [ + + ]: 41433 : if (ScanDirectionIsForward(dir))
2210 : : {
2211 : : /* There could be dead pages to the left, so not this: */
2212 : : /* Assert(P_LEFTMOST(opaque)); */
2213 : :
9279 tgl@sss.pgh.pa.us 2214 [ + + ]: 41403 : start = P_FIRSTDATAKEY(opaque);
2215 : : }
10327 bruce@momjian.us 2216 [ + - ]: 30 : else if (ScanDirectionIsBackward(dir))
2217 : : {
9279 tgl@sss.pgh.pa.us 2218 [ - + ]: 30 : Assert(P_RIGHTMOST(opaque));
2219 : :
2220 : 30 : start = PageGetMaxOffsetNumber(page);
2221 : : }
2222 : : else
2223 : : {
8184 tgl@sss.pgh.pa.us 2224 [ # # ]:UBC 0 : elog(ERROR, "invalid scan direction: %d", (int) dir);
2225 : : start = 0; /* keep compiler quiet */
2226 : : }
2227 : :
2228 : : /*
2229 : : * Now load data from the first page of the scan.
2230 : : */
424 pg@bowt.ie 2231 [ + + ]:CBC 41433 : if (!_bt_readfirstpage(scan, start, dir))
2232 : 891 : return false;
2233 : :
398 2234 : 40542 : _bt_returnitem(scan, so);
7163 tgl@sss.pgh.pa.us 2235 : 40542 : return true;
2236 : : }
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