Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * toast_internals.c
4 : : * Functions for internal use by the TOAST system.
5 : : *
6 : : * Copyright (c) 2000-2025, PostgreSQL Global Development Group
7 : : *
8 : : * IDENTIFICATION
9 : : * src/backend/access/common/toast_internals.c
10 : : *
11 : : *-------------------------------------------------------------------------
12 : : */
13 : :
14 : : #include "postgres.h"
15 : :
16 : : #include "access/detoast.h"
17 : : #include "access/genam.h"
18 : : #include "access/heapam.h"
19 : : #include "access/heaptoast.h"
20 : : #include "access/table.h"
21 : : #include "access/toast_internals.h"
22 : : #include "access/xact.h"
23 : : #include "catalog/catalog.h"
24 : : #include "miscadmin.h"
25 : : #include "utils/fmgroids.h"
26 : : #include "utils/rel.h"
27 : : #include "utils/snapmgr.h"
28 : :
29 : : static bool toastrel_valueid_exists(Relation toastrel, Oid valueid);
30 : : static bool toastid_valueid_exists(Oid toastrelid, Oid valueid);
31 : :
32 : : /* ----------
33 : : * toast_compress_datum -
34 : : *
35 : : * Create a compressed version of a varlena datum
36 : : *
37 : : * If we fail (ie, compressed result is actually bigger than original)
38 : : * then return NULL. We must not use compressed data if it'd expand
39 : : * the tuple!
40 : : *
41 : : * We use VAR{SIZE,DATA}_ANY so we can handle short varlenas here without
42 : : * copying them. But we can't handle external or compressed datums.
43 : : * ----------
44 : : */
45 : : Datum
1683 rhaas@postgresql.org 46 :CBC 26551 : toast_compress_datum(Datum value, char cmethod)
47 : : {
48 : 26551 : struct varlena *tmp = NULL;
49 : : int32 valsize;
1629 tgl@sss.pgh.pa.us 50 : 26551 : ToastCompressionId cmid = TOAST_INVALID_COMPRESSION_ID;
51 : :
2303 rhaas@postgresql.org 52 [ - + ]: 26551 : Assert(!VARATT_IS_EXTERNAL(DatumGetPointer(value)));
53 [ - + ]: 26551 : Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
54 : :
1683 55 [ - + - - : 26551 : valsize = VARSIZE_ANY_EXHDR(DatumGetPointer(value));
- - - - +
+ ]
56 : :
57 : : /* If the compression method is not valid, use the current default */
1614 tgl@sss.pgh.pa.us 58 [ + + ]: 26551 : if (!CompressionMethodIsValid(cmethod))
59 : 26509 : cmethod = default_toast_compression;
60 : :
61 : : /*
62 : : * Call appropriate compression routine for the compression method.
63 : : */
1683 rhaas@postgresql.org 64 [ + + - ]: 26551 : switch (cmethod)
65 : : {
66 : 26530 : case TOAST_PGLZ_COMPRESSION:
80 peter@eisentraut.org 67 :GNC 26530 : tmp = pglz_compress_datum((const struct varlena *) DatumGetPointer(value));
1683 rhaas@postgresql.org 68 :CBC 26530 : cmid = TOAST_PGLZ_COMPRESSION_ID;
69 : 26530 : break;
70 : 21 : case TOAST_LZ4_COMPRESSION:
80 peter@eisentraut.org 71 :GNC 21 : tmp = lz4_compress_datum((const struct varlena *) DatumGetPointer(value));
1683 rhaas@postgresql.org 72 :CBC 21 : cmid = TOAST_LZ4_COMPRESSION_ID;
73 : 21 : break;
1683 rhaas@postgresql.org 74 :UBC 0 : default:
75 [ # # ]: 0 : elog(ERROR, "invalid compression method %c", cmethod);
76 : : }
77 : :
1683 rhaas@postgresql.org 78 [ + + ]:CBC 26551 : if (tmp == NULL)
79 : 6297 : return PointerGetDatum(NULL);
80 : :
81 : : /*
82 : : * We recheck the actual size even if compression reports success, because
83 : : * it might be satisfied with having saved as little as one byte in the
84 : : * compressed data --- which could turn into a net loss once you consider
85 : : * header and alignment padding. Worst case, the compressed format might
86 : : * require three padding bytes (plus header, which is included in
87 : : * VARSIZE(tmp)), whereas the uncompressed format would take only one
88 : : * header byte and no padding if the value is short enough. So we insist
89 : : * on a savings of more than 2 bytes to ensure we have a gain.
90 : : */
91 [ + - ]: 20254 : if (VARSIZE(tmp) < valsize - 2)
92 : : {
93 : : /* successful compression */
94 [ - + ]: 20254 : Assert(cmid != TOAST_INVALID_COMPRESSION_ID);
1680 tgl@sss.pgh.pa.us 95 [ + - - + : 20254 : TOAST_COMPRESS_SET_SIZE_AND_COMPRESS_METHOD(tmp, valsize, cmid);
+ + - + ]
2303 rhaas@postgresql.org 96 : 20254 : return PointerGetDatum(tmp);
97 : : }
98 : : else
99 : : {
100 : : /* incompressible data */
2303 rhaas@postgresql.org 101 :UBC 0 : pfree(tmp);
102 : 0 : return PointerGetDatum(NULL);
103 : : }
104 : : }
105 : :
106 : : /* ----------
107 : : * toast_save_datum -
108 : : *
109 : : * Save one single datum into the secondary relation and return
110 : : * a Datum reference for it.
111 : : *
112 : : * rel: the main relation we're working with (not the toast rel!)
113 : : * value: datum to be pushed to toast storage
114 : : * oldexternal: if not NULL, toast pointer previously representing the datum
115 : : * options: options to be passed to heap_insert() for toast rows
116 : : * ----------
117 : : */
118 : : Datum
2303 rhaas@postgresql.org 119 :CBC 8422 : toast_save_datum(Relation rel, Datum value,
120 : : struct varlena *oldexternal, int options)
121 : : {
122 : : Relation toastrel;
123 : : Relation *toastidxs;
124 : : TupleDesc toasttupDesc;
125 : 8422 : CommandId mycid = GetCurrentCommandId(true);
126 : : struct varlena *result;
127 : : struct varatt_external toast_pointer;
128 : 8422 : int32 chunk_seq = 0;
129 : : char *data_p;
130 : : int32 data_todo;
131 : 8422 : Pointer dval = DatumGetPointer(value);
132 : : int num_indexes;
133 : : int validIndex;
134 : :
83 peter@eisentraut.org 135 [ - + ]:GNC 8422 : Assert(!VARATT_IS_EXTERNAL(dval));
136 : :
137 : : /*
138 : : * Open the toast relation and its indexes. We can use the index to check
139 : : * uniqueness of the OID we assign to the toasted item, even though it has
140 : : * additional columns besides OID.
141 : : */
2303 rhaas@postgresql.org 142 :CBC 8422 : toastrel = table_open(rel->rd_rel->reltoastrelid, RowExclusiveLock);
143 : 8422 : toasttupDesc = toastrel->rd_att;
144 : :
145 : : /* Open all the toast indexes and look for the valid one */
146 : 8422 : validIndex = toast_open_indexes(toastrel,
147 : : RowExclusiveLock,
148 : : &toastidxs,
149 : : &num_indexes);
150 : :
151 : : /*
152 : : * Get the data pointer and length, and compute va_rawsize and va_extinfo.
153 : : *
154 : : * va_rawsize is the size of the equivalent fully uncompressed datum, so
155 : : * we have to adjust for short headers.
156 : : *
157 : : * va_extinfo stored the actual size of the data payload in the toast
158 : : * records and the compression method in first 2 bits if data is
159 : : * compressed.
160 : : */
161 [ + + ]: 8422 : if (VARATT_IS_SHORT(dval))
162 : : {
2303 rhaas@postgresql.org 163 :GBC 3 : data_p = VARDATA_SHORT(dval);
164 : 3 : data_todo = VARSIZE_SHORT(dval) - VARHDRSZ_SHORT;
165 : 3 : toast_pointer.va_rawsize = data_todo + VARHDRSZ; /* as if not short */
1683 166 : 3 : toast_pointer.va_extinfo = data_todo;
167 : : }
2303 rhaas@postgresql.org 168 [ + + ]:CBC 8419 : else if (VARATT_IS_COMPRESSED(dval))
169 : : {
170 : 5198 : data_p = VARDATA(dval);
171 : 5198 : data_todo = VARSIZE(dval) - VARHDRSZ;
172 : : /* rawsize in a compressed datum is just the size of the payload */
1680 tgl@sss.pgh.pa.us 173 : 5198 : toast_pointer.va_rawsize = VARDATA_COMPRESSED_GET_EXTSIZE(dval) + VARHDRSZ;
174 : :
175 : : /* set external size and compression method */
176 [ + + - + ]: 5198 : VARATT_EXTERNAL_SET_SIZE_AND_COMPRESS_METHOD(toast_pointer, data_todo,
177 : : VARDATA_COMPRESSED_GET_COMPRESS_METHOD(dval));
178 : : /* Assert that the numbers look like it's compressed */
2303 rhaas@postgresql.org 179 [ - + ]: 5198 : Assert(VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer));
180 : : }
181 : : else
182 : : {
183 : 3221 : data_p = VARDATA(dval);
184 : 3221 : data_todo = VARSIZE(dval) - VARHDRSZ;
185 : 3221 : toast_pointer.va_rawsize = VARSIZE(dval);
1683 186 : 3221 : toast_pointer.va_extinfo = data_todo;
187 : : }
188 : :
189 : : /*
190 : : * Insert the correct table OID into the result TOAST pointer.
191 : : *
192 : : * Normally this is the actual OID of the target toast table, but during
193 : : * table-rewriting operations such as CLUSTER, we have to insert the OID
194 : : * of the table's real permanent toast table instead. rd_toastoid is set
195 : : * if we have to substitute such an OID.
196 : : */
2303 197 [ + + ]: 8422 : if (OidIsValid(rel->rd_toastoid))
198 : 300 : toast_pointer.va_toastrelid = rel->rd_toastoid;
199 : : else
200 : 8122 : toast_pointer.va_toastrelid = RelationGetRelid(toastrel);
201 : :
202 : : /*
203 : : * Choose an OID to use as the value ID for this toast value.
204 : : *
205 : : * Normally we just choose an unused OID within the toast table. But
206 : : * during table-rewriting operations where we are preserving an existing
207 : : * toast table OID, we want to preserve toast value OIDs too. So, if
208 : : * rd_toastoid is set and we had a prior external value from that same
209 : : * toast table, re-use its value ID. If we didn't have a prior external
210 : : * value (which is a corner case, but possible if the table's attstorage
211 : : * options have been changed), we have to pick a value ID that doesn't
212 : : * conflict with either new or existing toast value OIDs.
213 : : */
214 [ + + ]: 8422 : if (!OidIsValid(rel->rd_toastoid))
215 : : {
216 : : /* normal case: just choose an unused OID */
217 : 8122 : toast_pointer.va_valueid =
218 : 8122 : GetNewOidWithIndex(toastrel,
219 : 8122 : RelationGetRelid(toastidxs[validIndex]),
220 : : (AttrNumber) 1);
221 : : }
222 : : else
223 : : {
224 : : /* rewrite case: check to see if value was in old toast table */
225 : 300 : toast_pointer.va_valueid = InvalidOid;
226 [ + + ]: 300 : if (oldexternal != NULL)
227 : : {
228 : : struct varatt_external old_toast_pointer;
229 : :
230 [ - + - + ]: 297 : Assert(VARATT_IS_EXTERNAL_ONDISK(oldexternal));
231 : : /* Must copy to access aligned fields */
232 [ - + - + : 297 : VARATT_EXTERNAL_GET_POINTER(old_toast_pointer, oldexternal);
+ - - + -
+ ]
233 [ + - ]: 297 : if (old_toast_pointer.va_toastrelid == rel->rd_toastoid)
234 : : {
235 : : /* This value came from the old toast table; reuse its OID */
236 : 297 : toast_pointer.va_valueid = old_toast_pointer.va_valueid;
237 : :
238 : : /*
239 : : * There is a corner case here: the table rewrite might have
240 : : * to copy both live and recently-dead versions of a row, and
241 : : * those versions could easily reference the same toast value.
242 : : * When we copy the second or later version of such a row,
243 : : * reusing the OID will mean we select an OID that's already
244 : : * in the new toast table. Check for that, and if so, just
245 : : * fall through without writing the data again.
246 : : *
247 : : * While annoying and ugly-looking, this is a good thing
248 : : * because it ensures that we wind up with only one copy of
249 : : * the toast value when there is only one copy in the old
250 : : * toast table. Before we detected this case, we'd have made
251 : : * multiple copies, wasting space; and what's worse, the
252 : : * copies belonging to already-deleted heap tuples would not
253 : : * be reclaimed by VACUUM.
254 : : */
255 [ + + ]: 297 : if (toastrel_valueid_exists(toastrel,
256 : : toast_pointer.va_valueid))
257 : : {
258 : : /* Match, so short-circuit the data storage loop below */
2303 rhaas@postgresql.org 259 :GBC 1 : data_todo = 0;
260 : : }
261 : : }
262 : : }
2303 rhaas@postgresql.org 263 [ + + ]:CBC 300 : if (toast_pointer.va_valueid == InvalidOid)
264 : : {
265 : : /*
266 : : * new value; must choose an OID that doesn't conflict in either
267 : : * old or new toast table
268 : : */
269 : : do
270 : : {
2303 rhaas@postgresql.org 271 :GBC 3 : toast_pointer.va_valueid =
272 : 3 : GetNewOidWithIndex(toastrel,
273 : 3 : RelationGetRelid(toastidxs[validIndex]),
274 : : (AttrNumber) 1);
275 [ - + ]: 3 : } while (toastid_valueid_exists(rel->rd_toastoid,
276 : : toast_pointer.va_valueid));
277 : : }
278 : : }
279 : :
280 : : /*
281 : : * Split up the item into chunks
282 : : */
2303 rhaas@postgresql.org 283 [ + + ]:CBC 39487 : while (data_todo > 0)
284 : : {
285 : : HeapTuple toasttup;
286 : : Datum t_values[3];
42 peter@eisentraut.org 287 :GNC 31065 : bool t_isnull[3] = {0};
288 : : union
289 : : {
290 : : struct varlena hdr;
291 : : /* this is to make the union big enough for a chunk: */
292 : : char data[TOAST_MAX_CHUNK_SIZE + VARHDRSZ];
293 : : /* ensure union is aligned well enough: */
294 : : int32 align_it;
295 : : } chunk_data;
296 : : int32 chunk_size;
297 : :
2303 rhaas@postgresql.org 298 [ - + ]:CBC 31065 : CHECK_FOR_INTERRUPTS();
299 : :
300 : : /*
301 : : * Calculate the size of this chunk
302 : : */
303 : 31065 : chunk_size = Min(TOAST_MAX_CHUNK_SIZE, data_todo);
304 : :
305 : : /*
306 : : * Build a tuple and store it
307 : : */
42 peter@eisentraut.org 308 :GNC 31065 : t_values[0] = ObjectIdGetDatum(toast_pointer.va_valueid);
2303 rhaas@postgresql.org 309 :CBC 31065 : t_values[1] = Int32GetDatum(chunk_seq++);
310 : 31065 : SET_VARSIZE(&chunk_data, chunk_size + VARHDRSZ);
311 : 31065 : memcpy(VARDATA(&chunk_data), data_p, chunk_size);
42 peter@eisentraut.org 312 :GNC 31065 : t_values[2] = PointerGetDatum(&chunk_data);
313 : :
2303 rhaas@postgresql.org 314 :CBC 31065 : toasttup = heap_form_tuple(toasttupDesc, t_values, t_isnull);
315 : :
316 : 31065 : heap_insert(toastrel, toasttup, mycid, options, NULL);
317 : :
318 : : /*
319 : : * Create the index entry. We cheat a little here by not using
320 : : * FormIndexDatum: this relies on the knowledge that the index columns
321 : : * are the same as the initial columns of the table for all the
322 : : * indexes. We also cheat by not providing an IndexInfo: this is okay
323 : : * for now because btree doesn't need one, but we might have to be
324 : : * more honest someday.
325 : : *
326 : : * Note also that there had better not be any user-created index on
327 : : * the TOAST table, since we don't bother to update anything else.
328 : : */
42 peter@eisentraut.org 329 [ + + ]:GNC 62130 : for (int i = 0; i < num_indexes; i++)
330 : : {
331 : : /* Only index relations marked as ready can be updated */
2303 rhaas@postgresql.org 332 [ + - ]:CBC 31065 : if (toastidxs[i]->rd_index->indisready)
333 : 31065 : index_insert(toastidxs[i], t_values, t_isnull,
334 : : &(toasttup->t_self),
335 : : toastrel,
336 : 31065 : toastidxs[i]->rd_index->indisunique ?
337 : : UNIQUE_CHECK_YES : UNIQUE_CHECK_NO,
338 : : false, NULL);
339 : : }
340 : :
341 : : /*
342 : : * Free memory
343 : : */
344 : 31065 : heap_freetuple(toasttup);
345 : :
346 : : /*
347 : : * Move on to next chunk
348 : : */
349 : 31065 : data_todo -= chunk_size;
350 : 31065 : data_p += chunk_size;
351 : : }
352 : :
353 : : /*
354 : : * Done - close toast relation and its indexes but keep the lock until
355 : : * commit, so as a concurrent reindex done directly on the toast relation
356 : : * would be able to wait for this transaction.
357 : : */
1419 michael@paquier.xyz 358 : 8422 : toast_close_indexes(toastidxs, num_indexes, NoLock);
359 : 8422 : table_close(toastrel, NoLock);
360 : :
361 : : /*
362 : : * Create the TOAST pointer value that we'll return
363 : : */
2303 rhaas@postgresql.org 364 : 8422 : result = (struct varlena *) palloc(TOAST_POINTER_SIZE);
365 : 8422 : SET_VARTAG_EXTERNAL(result, VARTAG_ONDISK);
366 : 8422 : memcpy(VARDATA_EXTERNAL(result), &toast_pointer, sizeof(toast_pointer));
367 : :
368 : 8422 : return PointerGetDatum(result);
369 : : }
370 : :
371 : : /* ----------
372 : : * toast_delete_datum -
373 : : *
374 : : * Delete a single external stored value.
375 : : * ----------
376 : : */
377 : : void
378 : 700 : toast_delete_datum(Relation rel, Datum value, bool is_speculative)
379 : : {
380 : 700 : struct varlena *attr = (struct varlena *) DatumGetPointer(value);
381 : : struct varatt_external toast_pointer;
382 : : Relation toastrel;
383 : : Relation *toastidxs;
384 : : ScanKeyData toastkey;
385 : : SysScanDesc toastscan;
386 : : HeapTuple toasttup;
387 : : int num_indexes;
388 : : int validIndex;
389 : :
390 [ - + - + ]: 700 : if (!VARATT_IS_EXTERNAL_ONDISK(attr))
2303 rhaas@postgresql.org 391 :UBC 0 : return;
392 : :
393 : : /* Must copy to access aligned fields */
2303 rhaas@postgresql.org 394 [ - + - + :CBC 700 : VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
+ - - + -
+ ]
395 : :
396 : : /*
397 : : * Open the toast relation and its indexes
398 : : */
399 : 700 : toastrel = table_open(toast_pointer.va_toastrelid, RowExclusiveLock);
400 : :
401 : : /* Fetch valid relation used for process */
402 : 700 : validIndex = toast_open_indexes(toastrel,
403 : : RowExclusiveLock,
404 : : &toastidxs,
405 : : &num_indexes);
406 : :
407 : : /*
408 : : * Setup a scan key to find chunks with matching va_valueid
409 : : */
410 : 700 : ScanKeyInit(&toastkey,
411 : : (AttrNumber) 1,
412 : : BTEqualStrategyNumber, F_OIDEQ,
413 : : ObjectIdGetDatum(toast_pointer.va_valueid));
414 : :
415 : : /*
416 : : * Find all the chunks. (We don't actually care whether we see them in
417 : : * sequence or not, but since we've already locked the index we might as
418 : : * well use systable_beginscan_ordered.)
419 : : */
420 : 700 : toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
421 : : get_toast_snapshot(), 1, &toastkey);
422 [ + + ]: 3271 : while ((toasttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
423 : : {
424 : : /*
425 : : * Have a chunk, delete it
426 : : */
427 [ + + ]: 2571 : if (is_speculative)
428 : 5 : heap_abort_speculative(toastrel, &toasttup->t_self);
429 : : else
430 : 2566 : simple_heap_delete(toastrel, &toasttup->t_self);
431 : : }
432 : :
433 : : /*
434 : : * End scan and close relations but keep the lock until commit, so as a
435 : : * concurrent reindex done directly on the toast relation would be able to
436 : : * wait for this transaction.
437 : : */
438 : 700 : systable_endscan_ordered(toastscan);
1419 michael@paquier.xyz 439 : 700 : toast_close_indexes(toastidxs, num_indexes, NoLock);
440 : 700 : table_close(toastrel, NoLock);
441 : : }
442 : :
443 : : /* ----------
444 : : * toastrel_valueid_exists -
445 : : *
446 : : * Test whether a toast value with the given ID exists in the toast relation.
447 : : * For safety, we consider a value to exist if there are either live or dead
448 : : * toast rows with that ID; see notes for GetNewOidWithIndex().
449 : : * ----------
450 : : */
451 : : static bool
2303 rhaas@postgresql.org 452 : 300 : toastrel_valueid_exists(Relation toastrel, Oid valueid)
453 : : {
454 : 300 : bool result = false;
455 : : ScanKeyData toastkey;
456 : : SysScanDesc toastscan;
457 : : int num_indexes;
458 : : int validIndex;
459 : : Relation *toastidxs;
460 : :
461 : : /* Fetch a valid index relation */
462 : 300 : validIndex = toast_open_indexes(toastrel,
463 : : RowExclusiveLock,
464 : : &toastidxs,
465 : : &num_indexes);
466 : :
467 : : /*
468 : : * Setup a scan key to find chunks with matching va_valueid
469 : : */
470 : 300 : ScanKeyInit(&toastkey,
471 : : (AttrNumber) 1,
472 : : BTEqualStrategyNumber, F_OIDEQ,
473 : : ObjectIdGetDatum(valueid));
474 : :
475 : : /*
476 : : * Is there any such chunk?
477 : : */
478 : 300 : toastscan = systable_beginscan(toastrel,
479 : 300 : RelationGetRelid(toastidxs[validIndex]),
480 : : true, SnapshotAny, 1, &toastkey);
481 : :
482 [ + + ]: 300 : if (systable_getnext(toastscan) != NULL)
2303 rhaas@postgresql.org 483 :GBC 1 : result = true;
484 : :
2303 rhaas@postgresql.org 485 :CBC 300 : systable_endscan(toastscan);
486 : :
487 : : /* Clean up */
488 : 300 : toast_close_indexes(toastidxs, num_indexes, RowExclusiveLock);
489 : :
490 : 300 : return result;
491 : : }
492 : :
493 : : /* ----------
494 : : * toastid_valueid_exists -
495 : : *
496 : : * As above, but work from toast rel's OID not an open relation
497 : : * ----------
498 : : */
499 : : static bool
2303 rhaas@postgresql.org 500 :GBC 3 : toastid_valueid_exists(Oid toastrelid, Oid valueid)
501 : : {
502 : : bool result;
503 : : Relation toastrel;
504 : :
505 : 3 : toastrel = table_open(toastrelid, AccessShareLock);
506 : :
507 : 3 : result = toastrel_valueid_exists(toastrel, valueid);
508 : :
509 : 3 : table_close(toastrel, AccessShareLock);
510 : :
511 : 3 : return result;
512 : : }
513 : :
514 : : /* ----------
515 : : * toast_get_valid_index
516 : : *
517 : : * Get OID of valid index associated to given toast relation. A toast
518 : : * relation can have only one valid index at the same time.
519 : : */
520 : : Oid
2303 rhaas@postgresql.org 521 :CBC 492 : toast_get_valid_index(Oid toastoid, LOCKMODE lock)
522 : : {
523 : : int num_indexes;
524 : : int validIndex;
525 : : Oid validIndexOid;
526 : : Relation *toastidxs;
527 : : Relation toastrel;
528 : :
529 : : /* Open the toast relation */
530 : 492 : toastrel = table_open(toastoid, lock);
531 : :
532 : : /* Look for the valid index of the toast relation */
533 : 492 : validIndex = toast_open_indexes(toastrel,
534 : : lock,
535 : : &toastidxs,
536 : : &num_indexes);
537 : 492 : validIndexOid = RelationGetRelid(toastidxs[validIndex]);
538 : :
539 : : /* Close the toast relation and all its indexes */
2046 noah@leadboat.com 540 : 492 : toast_close_indexes(toastidxs, num_indexes, NoLock);
541 : 492 : table_close(toastrel, NoLock);
542 : :
2303 rhaas@postgresql.org 543 : 492 : return validIndexOid;
544 : : }
545 : :
546 : : /* ----------
547 : : * toast_open_indexes
548 : : *
549 : : * Get an array of the indexes associated to the given toast relation
550 : : * and return as well the position of the valid index used by the toast
551 : : * relation in this array. It is the responsibility of the caller of this
552 : : * function to close the indexes as well as free them.
553 : : */
554 : : int
555 : 22310 : toast_open_indexes(Relation toastrel,
556 : : LOCKMODE lock,
557 : : Relation **toastidxs,
558 : : int *num_indexes)
559 : : {
560 : 22310 : int i = 0;
561 : 22310 : int res = 0;
562 : 22310 : bool found = false;
563 : : List *indexlist;
564 : : ListCell *lc;
565 : :
566 : : /* Get index list of the toast relation */
567 : 22310 : indexlist = RelationGetIndexList(toastrel);
568 [ - + ]: 22310 : Assert(indexlist != NIL);
569 : :
570 : 22310 : *num_indexes = list_length(indexlist);
571 : :
572 : : /* Open all the index relations */
573 : 22310 : *toastidxs = (Relation *) palloc(*num_indexes * sizeof(Relation));
574 [ + - + + : 44620 : foreach(lc, indexlist)
+ + ]
575 : 22310 : (*toastidxs)[i++] = index_open(lfirst_oid(lc), lock);
576 : :
577 : : /* Fetch the first valid index in list */
578 [ + - ]: 22310 : for (i = 0; i < *num_indexes; i++)
579 : : {
580 : 22310 : Relation toastidx = (*toastidxs)[i];
581 : :
582 [ + - ]: 22310 : if (toastidx->rd_index->indisvalid)
583 : : {
584 : 22310 : res = i;
585 : 22310 : found = true;
586 : 22310 : break;
587 : : }
588 : : }
589 : :
590 : : /*
591 : : * Free index list, not necessary anymore as relations are opened and a
592 : : * valid index has been found.
593 : : */
594 : 22310 : list_free(indexlist);
595 : :
596 : : /*
597 : : * The toast relation should have one valid index, so something is going
598 : : * wrong if there is nothing.
599 : : */
600 [ - + ]: 22310 : if (!found)
2303 rhaas@postgresql.org 601 [ # # ]:UBC 0 : elog(ERROR, "no valid index found for toast relation with Oid %u",
602 : : RelationGetRelid(toastrel));
603 : :
2303 rhaas@postgresql.org 604 :CBC 22310 : return res;
605 : : }
606 : :
607 : : /* ----------
608 : : * toast_close_indexes
609 : : *
610 : : * Close an array of indexes for a toast relation and free it. This should
611 : : * be called for a set of indexes opened previously with toast_open_indexes.
612 : : */
613 : : void
614 : 22307 : toast_close_indexes(Relation *toastidxs, int num_indexes, LOCKMODE lock)
615 : : {
616 : : int i;
617 : :
618 : : /* Close relations and clean up things */
619 [ + + ]: 44614 : for (i = 0; i < num_indexes; i++)
620 : 22307 : index_close(toastidxs[i], lock);
621 : 22307 : pfree(toastidxs);
622 : 22307 : }
623 : :
624 : : /* ----------
625 : : * get_toast_snapshot
626 : : *
627 : : * Return the TOAST snapshot. Detoasting *must* happen in the same
628 : : * transaction that originally fetched the toast pointer.
629 : : */
630 : : Snapshot
322 heikki.linnakangas@i 631 : 24240 : get_toast_snapshot(void)
632 : : {
633 : : /*
634 : : * We cannot directly check that detoasting happens in the same
635 : : * transaction that originally fetched the toast pointer, but at least
636 : : * check that the session has some active snapshots. It might not if, for
637 : : * example, a procedure fetches a toasted value into a local variable,
638 : : * commits, and then tries to detoast the value. Such coding is unsafe,
639 : : * because once we commit there is nothing to prevent the toast data from
640 : : * being deleted. (This is not very much protection, because in many
641 : : * scenarios the procedure would have already created a new transaction
642 : : * snapshot, preventing us from detecting the problem. But it's better
643 : : * than nothing.)
644 : : */
645 [ - + ]: 24240 : if (!HaveRegisteredOrActiveSnapshot())
1621 tgl@sss.pgh.pa.us 646 [ # # ]:UBC 0 : elog(ERROR, "cannot fetch toast data without an active snapshot");
647 : :
322 heikki.linnakangas@i 648 :CBC 24240 : return &SnapshotToastData;
649 : : }
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