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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * genam.c
4 : : * general index access method routines
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : *
10 : : * IDENTIFICATION
11 : : * src/backend/access/index/genam.c
12 : : *
13 : : * NOTES
14 : : * many of the old access method routines have been turned into
15 : : * macros and moved to genam.h -cim 4/30/91
16 : : *
17 : : *-------------------------------------------------------------------------
18 : : */
19 : :
20 : : #include "postgres.h"
21 : :
22 : : #include "access/genam.h"
23 : : #include "access/heapam.h"
24 : : #include "access/relscan.h"
25 : : #include "access/tableam.h"
26 : : #include "access/transam.h"
27 : : #include "catalog/index.h"
28 : : #include "lib/stringinfo.h"
29 : : #include "miscadmin.h"
30 : : #include "storage/bufmgr.h"
31 : : #include "storage/procarray.h"
32 : : #include "utils/acl.h"
33 : : #include "utils/injection_point.h"
34 : : #include "utils/lsyscache.h"
35 : : #include "utils/rel.h"
36 : : #include "utils/rls.h"
37 : : #include "utils/ruleutils.h"
38 : : #include "utils/snapmgr.h"
39 : :
40 : :
41 : : /* ----------------------------------------------------------------
42 : : * general access method routines
43 : : *
44 : : * All indexed access methods use an identical scan structure.
45 : : * We don't know how the various AMs do locking, however, so we don't
46 : : * do anything about that here.
47 : : *
48 : : * The intent is that an AM implementor will define a beginscan routine
49 : : * that calls RelationGetIndexScan, to fill in the scan, and then does
50 : : * whatever kind of locking he wants.
51 : : *
52 : : * At the end of a scan, the AM's endscan routine undoes the locking,
53 : : * but does *not* call IndexScanEnd --- the higher-level index_endscan
54 : : * routine does that. (We can't do it in the AM because index_endscan
55 : : * still needs to touch the IndexScanDesc after calling the AM.)
56 : : *
57 : : * Because of this, the AM does not have a choice whether to call
58 : : * RelationGetIndexScan or not; its beginscan routine must return an
59 : : * object made by RelationGetIndexScan. This is kinda ugly but not
60 : : * worth cleaning up now.
61 : : * ----------------------------------------------------------------
62 : : */
63 : :
64 : : /* ----------------
65 : : * RelationGetIndexScan -- Create and fill an IndexScanDesc.
66 : : *
67 : : * This routine creates an index scan structure and sets up initial
68 : : * contents for it.
69 : : *
70 : : * Parameters:
71 : : * indexRelation -- index relation for scan.
72 : : * nkeys -- count of scan keys (index qual conditions).
73 : : * norderbys -- count of index order-by operators.
74 : : *
75 : : * Returns:
76 : : * An initialized IndexScanDesc.
77 : : * ----------------
78 : : */
79 : : IndexScanDesc
80 : 10091741 : RelationGetIndexScan(Relation indexRelation, int nkeys, int norderbys)
81 : : {
82 : : IndexScanDesc scan;
83 : :
84 : 10091741 : scan = palloc_object(IndexScanDescData);
85 : :
86 : 10091741 : scan->heapRelation = NULL; /* may be set later */
87 : 10091741 : scan->xs_heapfetch = NULL;
88 : 10091741 : scan->indexRelation = indexRelation;
89 : 10091741 : scan->xs_snapshot = InvalidSnapshot; /* caller must initialize this */
90 : 10091741 : scan->numberOfKeys = nkeys;
91 : 10091741 : scan->numberOfOrderBys = norderbys;
92 : :
93 : : /*
94 : : * We allocate key workspace here, but it won't get filled until amrescan.
95 : : */
96 [ + + ]: 10091741 : if (nkeys > 0)
97 : 10083890 : scan->keyData = palloc_array(ScanKeyData, nkeys);
98 : : else
99 : 7851 : scan->keyData = NULL;
100 [ + + ]: 10091741 : if (norderbys > 0)
101 : 119 : scan->orderByData = palloc_array(ScanKeyData, norderbys);
102 : : else
103 : 10091622 : scan->orderByData = NULL;
104 : :
105 : 10091741 : scan->xs_want_itup = false; /* may be set later */
106 : :
107 : : /*
108 : : * During recovery we ignore killed tuples and don't bother to kill them
109 : : * either. We do this because the xmin on the primary node could easily be
110 : : * later than the xmin on the standby node, so that what the primary
111 : : * thinks is killed is supposed to be visible on standby. So for correct
112 : : * MVCC for queries during recovery we must ignore these hints and check
113 : : * all tuples. Do *not* set ignore_killed_tuples to true when running in a
114 : : * transaction that was started during recovery. xactStartedInRecovery
115 : : * should not be altered by index AMs.
116 : : */
117 : 10091741 : scan->kill_prior_tuple = false;
118 : 10091741 : scan->xactStartedInRecovery = TransactionStartedDuringRecovery();
119 : 10091741 : scan->ignore_killed_tuples = !scan->xactStartedInRecovery;
120 : :
121 : 10091741 : scan->opaque = NULL;
122 : 10091741 : scan->instrument = NULL;
123 : :
124 : 10091741 : scan->xs_itup = NULL;
125 : 10091741 : scan->xs_itupdesc = NULL;
126 : 10091741 : scan->xs_hitup = NULL;
127 : 10091741 : scan->xs_hitupdesc = NULL;
128 : :
129 : 10091741 : return scan;
130 : : }
131 : :
132 : : /* ----------------
133 : : * IndexScanEnd -- End an index scan.
134 : : *
135 : : * This routine just releases the storage acquired by
136 : : * RelationGetIndexScan(). Any AM-level resources are
137 : : * assumed to already have been released by the AM's
138 : : * endscan routine.
139 : : *
140 : : * Returns:
141 : : * None.
142 : : * ----------------
143 : : */
144 : : void
145 : 10090374 : IndexScanEnd(IndexScanDesc scan)
146 : : {
147 [ + + ]: 10090374 : if (scan->keyData != NULL)
148 : 10082547 : pfree(scan->keyData);
149 [ + + ]: 10090374 : if (scan->orderByData != NULL)
150 : 115 : pfree(scan->orderByData);
151 : :
152 : 10090374 : pfree(scan);
153 : 10090374 : }
154 : :
155 : : /*
156 : : * BuildIndexValueDescription
157 : : *
158 : : * Construct a string describing the contents of an index entry, in the
159 : : * form "(key_name, ...)=(key_value, ...)". This is currently used
160 : : * for building unique-constraint, exclusion-constraint error messages, and
161 : : * logical replication conflict error messages so only key columns of the index
162 : : * are checked and printed.
163 : : *
164 : : * Note that if the user does not have permissions to view all of the
165 : : * columns involved then a NULL is returned. Returning a partial key seems
166 : : * unlikely to be useful and we have no way to know which of the columns the
167 : : * user provided (unlike in ExecBuildSlotValueDescription).
168 : : *
169 : : * The passed-in values/nulls arrays are the "raw" input to the index AM,
170 : : * e.g. results of FormIndexDatum --- this is not necessarily what is stored
171 : : * in the index, but it's what the user perceives to be stored.
172 : : *
173 : : * Note: if you change anything here, check whether
174 : : * ExecBuildSlotPartitionKeyDescription() in execMain.c needs a similar
175 : : * change.
176 : : */
177 : : char *
178 : 753 : BuildIndexValueDescription(Relation indexRelation,
179 : : const Datum *values, const bool *isnull)
180 : : {
181 : : StringInfoData buf;
182 : : Form_pg_index idxrec;
183 : : int indnkeyatts;
184 : : int i;
185 : : int keyno;
186 : 753 : Oid indexrelid = RelationGetRelid(indexRelation);
187 : : Oid indrelid;
188 : : AclResult aclresult;
189 : :
190 : 753 : indnkeyatts = IndexRelationGetNumberOfKeyAttributes(indexRelation);
191 : :
192 : : /*
193 : : * Check permissions- if the user does not have access to view all of the
194 : : * key columns then return NULL to avoid leaking data.
195 : : *
196 : : * First check if RLS is enabled for the relation. If so, return NULL to
197 : : * avoid leaking data.
198 : : *
199 : : * Next we need to check table-level SELECT access and then, if there is
200 : : * no access there, check column-level permissions.
201 : : */
202 : 753 : idxrec = indexRelation->rd_index;
203 : 753 : indrelid = idxrec->indrelid;
204 : : Assert(indexrelid == idxrec->indexrelid);
205 : :
206 : : /* RLS check- if RLS is enabled then we don't return anything. */
207 [ + + ]: 753 : if (check_enable_rls(indrelid, InvalidOid, true) == RLS_ENABLED)
208 : 8 : return NULL;
209 : :
210 : : /* Table-level SELECT is enough, if the user has it */
211 : 745 : aclresult = pg_class_aclcheck(indrelid, GetUserId(), ACL_SELECT);
212 [ + + ]: 745 : if (aclresult != ACLCHECK_OK)
213 : : {
214 : : /*
215 : : * No table-level access, so step through the columns in the index and
216 : : * make sure the user has SELECT rights on all of them.
217 : : */
218 [ + - ]: 16 : for (keyno = 0; keyno < indnkeyatts; keyno++)
219 : : {
220 : 16 : AttrNumber attnum = idxrec->indkey.values[keyno];
221 : :
222 : : /*
223 : : * Note that if attnum == InvalidAttrNumber, then this is an index
224 : : * based on an expression and we return no detail rather than try
225 : : * to figure out what column(s) the expression includes and if the
226 : : * user has SELECT rights on them.
227 : : */
228 [ + - + + ]: 32 : if (attnum == InvalidAttrNumber ||
229 : 16 : pg_attribute_aclcheck(indrelid, attnum, GetUserId(),
230 : : ACL_SELECT) != ACLCHECK_OK)
231 : : {
232 : : /* No access, so clean up and return */
233 : 8 : return NULL;
234 : : }
235 : : }
236 : : }
237 : :
238 : 737 : initStringInfo(&buf);
239 : 737 : appendStringInfo(&buf, "(%s)=(",
240 : : pg_get_indexdef_columns(indexrelid, true));
241 : :
242 [ + + ]: 1736 : for (i = 0; i < indnkeyatts; i++)
243 : : {
244 : : char *val;
245 : :
246 [ + + ]: 999 : if (isnull[i])
247 : 12 : val = "null";
248 : : else
249 : : {
250 : : Oid foutoid;
251 : : bool typisvarlena;
252 : :
253 : : /*
254 : : * The provided data is not necessarily of the type stored in the
255 : : * index; rather it is of the index opclass's input type. So look
256 : : * at rd_opcintype not the index tupdesc.
257 : : *
258 : : * Note: this is a bit shaky for opclasses that have pseudotype
259 : : * input types such as ANYARRAY or RECORD. Currently, the
260 : : * typoutput functions associated with the pseudotypes will work
261 : : * okay, but we might have to try harder in future.
262 : : */
263 : 987 : getTypeOutputInfo(indexRelation->rd_opcintype[i],
264 : : &foutoid, &typisvarlena);
265 : 987 : val = OidOutputFunctionCall(foutoid, values[i]);
266 : : }
267 : :
268 [ + + ]: 999 : if (i > 0)
269 : 262 : appendStringInfoString(&buf, ", ");
270 : 999 : appendStringInfoString(&buf, val);
271 : : }
272 : :
273 : 737 : appendStringInfoChar(&buf, ')');
274 : :
275 : 737 : return buf.data;
276 : : }
277 : :
278 : : /*
279 : : * Get the snapshotConflictHorizon from the table entries pointed to by the
280 : : * index tuples being deleted using an AM-generic approach.
281 : : *
282 : : * This is a table_index_delete_tuples() shim used by index AMs that only need
283 : : * to consult the tableam to get a snapshotConflictHorizon value, and only
284 : : * expect to delete index tuples that are already known deletable (typically
285 : : * due to having LP_DEAD bits set). When a snapshotConflictHorizon value
286 : : * isn't needed in index AM's deletion WAL record, it is safe for it to skip
287 : : * calling here entirely.
288 : : *
289 : : * We assume that caller index AM uses the standard IndexTuple representation,
290 : : * with table TIDs stored in the t_tid field. We also expect (and assert)
291 : : * that the line pointers on page for 'itemnos' offsets are already marked
292 : : * LP_DEAD.
293 : : */
294 : : TransactionId
295 : 4 : index_compute_xid_horizon_for_tuples(Relation irel,
296 : : Relation hrel,
297 : : Buffer ibuf,
298 : : OffsetNumber *itemnos,
299 : : int nitems)
300 : : {
301 : : TM_IndexDeleteOp delstate;
302 : 4 : TransactionId snapshotConflictHorizon = InvalidTransactionId;
303 : 4 : Page ipage = BufferGetPage(ibuf);
304 : : IndexTuple itup;
305 : :
306 : : Assert(nitems > 0);
307 : :
308 : 4 : delstate.irel = irel;
309 : 4 : delstate.iblknum = BufferGetBlockNumber(ibuf);
310 : 4 : delstate.bottomup = false;
311 : 4 : delstate.bottomupfreespace = 0;
312 : 4 : delstate.ndeltids = 0;
313 : 4 : delstate.deltids = palloc_array(TM_IndexDelete, nitems);
314 : 4 : delstate.status = palloc_array(TM_IndexStatus, nitems);
315 : :
316 : : /* identify what the index tuples about to be deleted point to */
317 [ + + ]: 888 : for (int i = 0; i < nitems; i++)
318 : : {
319 : 884 : OffsetNumber offnum = itemnos[i];
320 : : ItemId iitemid;
321 : :
322 : 884 : iitemid = PageGetItemId(ipage, offnum);
323 : 884 : itup = (IndexTuple) PageGetItem(ipage, iitemid);
324 : :
325 : : Assert(ItemIdIsDead(iitemid));
326 : :
327 : 884 : ItemPointerCopy(&itup->t_tid, &delstate.deltids[i].tid);
328 : 884 : delstate.deltids[i].id = delstate.ndeltids;
329 : 884 : delstate.status[i].idxoffnum = offnum;
330 : 884 : delstate.status[i].knowndeletable = true; /* LP_DEAD-marked */
331 : 884 : delstate.status[i].promising = false; /* unused */
332 : 884 : delstate.status[i].freespace = 0; /* unused */
333 : :
334 : 884 : delstate.ndeltids++;
335 : : }
336 : :
337 : : /* determine the actual xid horizon */
338 : 4 : snapshotConflictHorizon = table_index_delete_tuples(hrel, &delstate);
339 : :
340 : : /* assert tableam agrees that all items are deletable */
341 : : Assert(delstate.ndeltids == nitems);
342 : :
343 : 4 : pfree(delstate.deltids);
344 : 4 : pfree(delstate.status);
345 : :
346 : 4 : return snapshotConflictHorizon;
347 : : }
348 : :
349 : :
350 : : /* ----------------------------------------------------------------
351 : : * heap-or-index-scan access to system catalogs
352 : : *
353 : : * These functions support system catalog accesses that normally use
354 : : * an index but need to be capable of being switched to heap scans
355 : : * if the system indexes are unavailable.
356 : : *
357 : : * The specified scan keys must be compatible with the named index.
358 : : * Generally this means that they must constrain either all columns
359 : : * of the index, or the first K columns of an N-column index.
360 : : *
361 : : * These routines could work with non-system tables, actually,
362 : : * but they're only useful when there is a known index to use with
363 : : * the given scan keys; so in practice they're only good for
364 : : * predetermined types of scans of system catalogs.
365 : : * ----------------------------------------------------------------
366 : : */
367 : :
368 : : /*
369 : : * systable_beginscan --- set up for heap-or-index scan
370 : : *
371 : : * rel: catalog to scan, already opened and suitably locked
372 : : * indexId: OID of index to conditionally use
373 : : * indexOK: if false, forces a heap scan (see notes below)
374 : : * snapshot: time qual to use (NULL for a recent catalog snapshot)
375 : : * nkeys, key: scan keys
376 : : *
377 : : * The attribute numbers in the scan key should be set for the heap case.
378 : : * If we choose to index, we convert them to 1..n to reference the index
379 : : * columns. Note this means there must be one scankey qualification per
380 : : * index column! This is checked by the Asserts in the normal, index-using
381 : : * case, but won't be checked if the heapscan path is taken.
382 : : *
383 : : * The routine checks the normal cases for whether an indexscan is safe,
384 : : * but caller can make additional checks and pass indexOK=false if needed.
385 : : * In standard case indexOK can simply be constant TRUE.
386 : : */
387 : : SysScanDesc
388 : 10018485 : systable_beginscan(Relation heapRelation,
389 : : Oid indexId,
390 : : bool indexOK,
391 : : Snapshot snapshot,
392 : : int nkeys, ScanKey key)
393 : : {
394 : : SysScanDesc sysscan;
395 : : Relation irel;
396 : :
397 [ + + ]: 10018485 : if (indexOK &&
398 [ + + ]: 9866734 : !IgnoreSystemIndexes &&
399 [ + + ]: 9791437 : !ReindexIsProcessingIndex(indexId))
400 : 9782590 : irel = index_open(indexId, AccessShareLock);
401 : : else
402 : 235895 : irel = NULL;
403 : :
404 : 10018478 : sysscan = palloc_object(SysScanDescData);
405 : :
406 : 10018478 : sysscan->heap_rel = heapRelation;
407 : 10018478 : sysscan->irel = irel;
408 : 10018478 : sysscan->slot = table_slot_create(heapRelation, NULL);
409 : :
410 [ + + ]: 10018478 : if (snapshot == NULL)
411 : : {
412 : 9309193 : Oid relid = RelationGetRelid(heapRelation);
413 : :
414 : 9309193 : snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
415 : 9309193 : sysscan->snapshot = snapshot;
416 : : }
417 : : else
418 : : {
419 : : /* Caller is responsible for any snapshot. */
420 : 709285 : sysscan->snapshot = NULL;
421 : : }
422 : :
423 : : /*
424 : : * If CheckXidAlive is set then set a flag to indicate that system table
425 : : * scan is in-progress. See detailed comments in xact.c where these
426 : : * variables are declared.
427 : : */
428 [ + + ]: 10018478 : if (TransactionIdIsValid(CheckXidAlive))
429 : 969 : bsysscan = true;
430 : :
431 [ + + ]: 10018478 : if (irel)
432 : : {
433 : : int i;
434 : : ScanKey idxkey;
435 : :
436 : 9782583 : idxkey = palloc_array(ScanKeyData, nkeys);
437 : :
438 : : /* Convert attribute numbers to be index column numbers. */
439 [ + + ]: 25631868 : for (i = 0; i < nkeys; i++)
440 : : {
441 : : int j;
442 : :
443 : 15849285 : memcpy(&idxkey[i], &key[i], sizeof(ScanKeyData));
444 : :
445 [ + - ]: 22945432 : for (j = 0; j < IndexRelationGetNumberOfAttributes(irel); j++)
446 : : {
447 [ + + ]: 22945432 : if (key[i].sk_attno == irel->rd_index->indkey.values[j])
448 : : {
449 : 15849285 : idxkey[i].sk_attno = j + 1;
450 : 15849285 : break;
451 : : }
452 : : }
453 [ - + ]: 15849285 : if (j == IndexRelationGetNumberOfAttributes(irel))
454 [ # # ]: 0 : elog(ERROR, "column is not in index");
455 : : }
456 : :
457 : 9782583 : sysscan->iscan = index_beginscan(heapRelation, irel,
458 : : snapshot, NULL, nkeys, 0,
459 : : SO_NONE);
460 : 9782583 : index_rescan(sysscan->iscan, idxkey, nkeys, NULL, 0);
461 : 9782583 : sysscan->scan = NULL;
462 : :
463 : 9782583 : pfree(idxkey);
464 : : }
465 : : else
466 : : {
467 : : /*
468 : : * We disallow synchronized scans when forced to use a heapscan on a
469 : : * catalog. In most cases the desired rows are near the front, so
470 : : * that the unpredictable start point of a syncscan is a serious
471 : : * disadvantage; and there are no compensating advantages, because
472 : : * it's unlikely that such scans will occur in parallel.
473 : : */
474 : 235895 : sysscan->scan = table_beginscan_strat(heapRelation, snapshot,
475 : : nkeys, key,
476 : : true, false);
477 : 235895 : sysscan->iscan = NULL;
478 : : }
479 : :
480 : 10018478 : return sysscan;
481 : : }
482 : :
483 : : /*
484 : : * HandleConcurrentAbort - Handle concurrent abort of the CheckXidAlive.
485 : : *
486 : : * Error out, if CheckXidAlive is aborted. We can't directly use
487 : : * TransactionIdDidAbort as after crash such transaction might not have been
488 : : * marked as aborted. See detailed comments in xact.c where the variable
489 : : * is declared.
490 : : */
491 : : static inline void
492 : 20842765 : HandleConcurrentAbort(void)
493 : : {
494 [ + + ]: 20842765 : if (TransactionIdIsValid(CheckXidAlive) &&
495 [ + + ]: 1598 : !TransactionIdIsInProgress(CheckXidAlive) &&
496 [ + - ]: 8 : !TransactionIdDidCommit(CheckXidAlive))
497 [ + - ]: 8 : ereport(ERROR,
498 : : (errcode(ERRCODE_TRANSACTION_ROLLBACK),
499 : : errmsg("transaction aborted during system catalog scan")));
500 : 20842757 : }
501 : :
502 : : /*
503 : : * systable_getnext --- get next tuple in a heap-or-index scan
504 : : *
505 : : * Returns NULL if no more tuples available.
506 : : *
507 : : * Note that returned tuple is a reference to data in a disk buffer;
508 : : * it must not be modified, and should be presumed inaccessible after
509 : : * next getnext() or endscan() call.
510 : : *
511 : : * XXX: It'd probably make sense to offer a slot based interface, at least
512 : : * optionally.
513 : : */
514 : : HeapTuple
515 : 20536522 : systable_getnext(SysScanDesc sysscan)
516 : : {
517 : 20536522 : HeapTuple htup = NULL;
518 : :
519 [ + + ]: 20536522 : if (sysscan->irel)
520 : : {
521 [ + + ]: 18184342 : if (index_getnext_slot(sysscan->iscan, ForwardScanDirection, sysscan->slot))
522 : : {
523 : : bool shouldFree;
524 : :
525 : 14094676 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
526 : : Assert(!shouldFree);
527 : :
528 : : /*
529 : : * We currently don't need to support lossy index operators for
530 : : * any system catalog scan. It could be done here, using the scan
531 : : * keys to drive the operator calls, if we arranged to save the
532 : : * heap attnums during systable_beginscan(); this is practical
533 : : * because we still wouldn't need to support indexes on
534 : : * expressions.
535 : : */
536 [ - + ]: 14094676 : if (sysscan->iscan->xs_recheck)
537 [ # # ]: 0 : elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
538 : : }
539 : : }
540 : : else
541 : : {
542 [ + + ]: 2352180 : if (table_scan_getnextslot(sysscan->scan, ForwardScanDirection, sysscan->slot))
543 : : {
544 : : bool shouldFree;
545 : :
546 : 2295554 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
547 : : Assert(!shouldFree);
548 : : }
549 : : }
550 : :
551 : : /*
552 : : * Handle the concurrent abort while fetching the catalog tuple during
553 : : * logical streaming of a transaction.
554 : : */
555 : 20536514 : HandleConcurrentAbort();
556 : :
557 : 20536506 : return htup;
558 : : }
559 : :
560 : : /*
561 : : * systable_recheck_tuple --- recheck visibility of most-recently-fetched tuple
562 : : *
563 : : * In particular, determine if this tuple would be visible to a catalog scan
564 : : * that started now. We don't handle the case of a non-MVCC scan snapshot,
565 : : * because no caller needs that yet.
566 : : *
567 : : * This is useful to test whether an object was deleted while we waited to
568 : : * acquire lock on it.
569 : : *
570 : : * Note: we don't actually *need* the tuple to be passed in, but it's a
571 : : * good crosscheck that the caller is interested in the right tuple.
572 : : */
573 : : bool
574 : 166030 : systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup)
575 : : {
576 : : Snapshot freshsnap;
577 : : bool result;
578 : :
579 : : Assert(tup == ExecFetchSlotHeapTuple(sysscan->slot, false, NULL));
580 : :
581 : 166030 : freshsnap = GetCatalogSnapshot(RelationGetRelid(sysscan->heap_rel));
582 : 166030 : freshsnap = RegisterSnapshot(freshsnap);
583 : :
584 : 166030 : result = table_tuple_satisfies_snapshot(sysscan->heap_rel,
585 : 166030 : sysscan->slot,
586 : : freshsnap);
587 : 166030 : UnregisterSnapshot(freshsnap);
588 : :
589 : : /*
590 : : * Handle the concurrent abort while fetching the catalog tuple during
591 : : * logical streaming of a transaction.
592 : : */
593 : 166030 : HandleConcurrentAbort();
594 : :
595 : 166030 : return result;
596 : : }
597 : :
598 : : /*
599 : : * systable_endscan --- close scan, release resources
600 : : *
601 : : * Note that it's still up to the caller to close the heap relation.
602 : : */
603 : : void
604 : 10017884 : systable_endscan(SysScanDesc sysscan)
605 : : {
606 [ + - ]: 10017884 : if (sysscan->slot)
607 : : {
608 : 10017884 : ExecDropSingleTupleTableSlot(sysscan->slot);
609 : 10017884 : sysscan->slot = NULL;
610 : : }
611 : :
612 [ + + ]: 10017884 : if (sysscan->irel)
613 : : {
614 : 9782012 : index_endscan(sysscan->iscan);
615 : 9782012 : index_close(sysscan->irel, AccessShareLock);
616 : : }
617 : : else
618 : 235872 : table_endscan(sysscan->scan);
619 : :
620 [ + + ]: 10017884 : if (sysscan->snapshot)
621 : 9308607 : UnregisterSnapshot(sysscan->snapshot);
622 : :
623 : : /*
624 : : * Reset the bsysscan flag at the end of the systable scan. See detailed
625 : : * comments in xact.c where these variables are declared.
626 : : */
627 [ + + ]: 10017884 : if (TransactionIdIsValid(CheckXidAlive))
628 : 961 : bsysscan = false;
629 : :
630 : 10017884 : pfree(sysscan);
631 : 10017884 : }
632 : :
633 : :
634 : : /*
635 : : * systable_beginscan_ordered --- set up for ordered catalog scan
636 : : *
637 : : * These routines have essentially the same API as systable_beginscan etc,
638 : : * except that they guarantee to return multiple matching tuples in
639 : : * index order. Also, for largely historical reasons, the index to use
640 : : * is opened and locked by the caller, not here.
641 : : *
642 : : * Currently we do not support non-index-based scans here. (In principle
643 : : * we could do a heapscan and sort, but the uses are in places that
644 : : * probably don't need to still work with corrupted catalog indexes.)
645 : : * For the moment, therefore, these functions are merely the thinest of
646 : : * wrappers around index_beginscan/index_getnext_slot. The main reason for
647 : : * their existence is to centralize possible future support of lossy operators
648 : : * in catalog scans.
649 : : */
650 : : SysScanDesc
651 : 37564 : systable_beginscan_ordered(Relation heapRelation,
652 : : Relation indexRelation,
653 : : Snapshot snapshot,
654 : : int nkeys, ScanKey key)
655 : : {
656 : : SysScanDesc sysscan;
657 : : int i;
658 : : ScanKey idxkey;
659 : :
660 : : /* REINDEX can probably be a hard error here ... */
661 [ - + ]: 37564 : if (ReindexIsProcessingIndex(RelationGetRelid(indexRelation)))
662 [ # # ]: 0 : ereport(ERROR,
663 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
664 : : errmsg("cannot access index \"%s\" while it is being reindexed",
665 : : RelationGetRelationName(indexRelation))));
666 : : /* ... but we only throw a warning about violating IgnoreSystemIndexes */
667 [ - + ]: 37564 : if (IgnoreSystemIndexes)
668 [ # # ]: 0 : elog(WARNING, "using index \"%s\" despite IgnoreSystemIndexes",
669 : : RelationGetRelationName(indexRelation));
670 : :
671 : 37564 : sysscan = palloc_object(SysScanDescData);
672 : :
673 : 37564 : sysscan->heap_rel = heapRelation;
674 : 37564 : sysscan->irel = indexRelation;
675 : 37564 : sysscan->slot = table_slot_create(heapRelation, NULL);
676 : :
677 [ + + ]: 37564 : if (snapshot == NULL)
678 : : {
679 : 5340 : Oid relid = RelationGetRelid(heapRelation);
680 : :
681 : 5340 : snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
682 : 5340 : sysscan->snapshot = snapshot;
683 : : }
684 : : else
685 : : {
686 : : /* Caller is responsible for any snapshot. */
687 : 32224 : sysscan->snapshot = NULL;
688 : : }
689 : :
690 : 37564 : idxkey = palloc_array(ScanKeyData, nkeys);
691 : :
692 : : /* Convert attribute numbers to be index column numbers. */
693 [ + + ]: 73105 : for (i = 0; i < nkeys; i++)
694 : : {
695 : : int j;
696 : :
697 : 35541 : memcpy(&idxkey[i], &key[i], sizeof(ScanKeyData));
698 : :
699 [ + - ]: 37588 : for (j = 0; j < IndexRelationGetNumberOfAttributes(indexRelation); j++)
700 : : {
701 [ + + ]: 37588 : if (key[i].sk_attno == indexRelation->rd_index->indkey.values[j])
702 : : {
703 : 35541 : idxkey[i].sk_attno = j + 1;
704 : 35541 : break;
705 : : }
706 : : }
707 [ - + ]: 35541 : if (j == IndexRelationGetNumberOfAttributes(indexRelation))
708 [ # # ]: 0 : elog(ERROR, "column is not in index");
709 : : }
710 : :
711 : : /*
712 : : * If CheckXidAlive is set then set a flag to indicate that system table
713 : : * scan is in-progress. See detailed comments in xact.c where these
714 : : * variables are declared.
715 : : */
716 [ - + ]: 37564 : if (TransactionIdIsValid(CheckXidAlive))
717 : 0 : bsysscan = true;
718 : :
719 : 37564 : sysscan->iscan = index_beginscan(heapRelation, indexRelation,
720 : : snapshot, NULL, nkeys, 0,
721 : : SO_NONE);
722 : 37564 : index_rescan(sysscan->iscan, idxkey, nkeys, NULL, 0);
723 : 37564 : sysscan->scan = NULL;
724 : :
725 : 37564 : pfree(idxkey);
726 : :
727 : 37564 : return sysscan;
728 : : }
729 : :
730 : : /*
731 : : * systable_getnext_ordered --- get next tuple in an ordered catalog scan
732 : : */
733 : : HeapTuple
734 : 140224 : systable_getnext_ordered(SysScanDesc sysscan, ScanDirection direction)
735 : : {
736 : 140224 : HeapTuple htup = NULL;
737 : :
738 : : Assert(sysscan->irel);
739 [ + + ]: 140224 : if (index_getnext_slot(sysscan->iscan, direction, sysscan->slot))
740 : 103512 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, NULL);
741 : :
742 : : /* See notes in systable_getnext */
743 [ + + - + ]: 140221 : if (htup && sysscan->iscan->xs_recheck)
744 [ # # ]: 0 : elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
745 : :
746 : : /*
747 : : * Handle the concurrent abort while fetching the catalog tuple during
748 : : * logical streaming of a transaction.
749 : : */
750 : 140221 : HandleConcurrentAbort();
751 : :
752 : 140221 : return htup;
753 : : }
754 : :
755 : : /*
756 : : * systable_endscan_ordered --- close scan, release resources
757 : : */
758 : : void
759 : 37553 : systable_endscan_ordered(SysScanDesc sysscan)
760 : : {
761 [ + - ]: 37553 : if (sysscan->slot)
762 : : {
763 : 37553 : ExecDropSingleTupleTableSlot(sysscan->slot);
764 : 37553 : sysscan->slot = NULL;
765 : : }
766 : :
767 : : Assert(sysscan->irel);
768 : 37553 : index_endscan(sysscan->iscan);
769 [ + + ]: 37553 : if (sysscan->snapshot)
770 : 5332 : UnregisterSnapshot(sysscan->snapshot);
771 : :
772 : : /*
773 : : * Reset the bsysscan flag at the end of the systable scan. See detailed
774 : : * comments in xact.c where these variables are declared.
775 : : */
776 [ - + ]: 37553 : if (TransactionIdIsValid(CheckXidAlive))
777 : 0 : bsysscan = false;
778 : :
779 : 37553 : pfree(sysscan);
780 : 37553 : }
781 : :
782 : : /*
783 : : * systable_inplace_update_begin --- update a row "in place" (overwrite it)
784 : : *
785 : : * Overwriting violates both MVCC and transactional safety, so the uses of
786 : : * this function in Postgres are extremely limited. This makes no effort to
787 : : * support updating cache key columns or other indexed columns. Nonetheless
788 : : * we find some places to use it. See README.tuplock section "Locking to
789 : : * write inplace-updated tables" and later sections for expectations of
790 : : * readers and writers of a table that gets inplace updates. Standard flow:
791 : : *
792 : : * ... [any slow preparation not requiring oldtup] ...
793 : : * systable_inplace_update_begin([...], &tup, &inplace_state);
794 : : * if (!HeapTupleIsValid(tup))
795 : : * elog(ERROR, [...]);
796 : : * ... [buffer is exclusive-locked; mutate "tup"] ...
797 : : * if (dirty)
798 : : * systable_inplace_update_finish(inplace_state, tup);
799 : : * else
800 : : * systable_inplace_update_cancel(inplace_state);
801 : : *
802 : : * The first several params duplicate the systable_beginscan() param list.
803 : : * "oldtupcopy" is an output parameter, assigned NULL if the key ceases to
804 : : * find a live tuple. (In PROC_IN_VACUUM, that is a low-probability transient
805 : : * condition.) If "oldtupcopy" gets non-NULL, you must pass output parameter
806 : : * "state" to systable_inplace_update_finish() or
807 : : * systable_inplace_update_cancel().
808 : : */
809 : : void
810 : 228974 : systable_inplace_update_begin(Relation relation,
811 : : Oid indexId,
812 : : bool indexOK,
813 : : Snapshot snapshot,
814 : : int nkeys, const ScanKeyData *key,
815 : : HeapTuple *oldtupcopy,
816 : : void **state)
817 : : {
818 : 228974 : int retries = 0;
819 : : SysScanDesc scan;
820 : : HeapTuple oldtup;
821 : : BufferHeapTupleTableSlot *bslot;
822 : :
823 : : /*
824 : : * For now, we don't allow parallel updates. Unlike a regular update,
825 : : * this should never create a combo CID, so it might be possible to relax
826 : : * this restriction, but not without more thought and testing. It's not
827 : : * clear that it would be useful, anyway.
828 : : */
829 [ - + ]: 228974 : if (IsInParallelMode())
830 [ # # ]: 0 : ereport(ERROR,
831 : : (errcode(ERRCODE_INVALID_TRANSACTION_STATE),
832 : : errmsg("cannot update tuples during a parallel operation")));
833 : :
834 : : /*
835 : : * Accept a snapshot argument, for symmetry, but this function advances
836 : : * its snapshot as needed to reach the tail of the updated tuple chain.
837 : : */
838 : : Assert(snapshot == NULL);
839 : :
840 : : Assert(IsInplaceUpdateRelation(relation) || !IsSystemRelation(relation));
841 : :
842 : : /* Loop for an exclusive-locked buffer of a non-updated tuple. */
843 : : do
844 : : {
845 : : TupleTableSlot *slot;
846 : :
847 [ + + ]: 228992 : CHECK_FOR_INTERRUPTS();
848 : :
849 : : /*
850 : : * Processes issuing heap_update (e.g. GRANT) at maximum speed could
851 : : * drive us to this error. A hostile table owner has stronger ways to
852 : : * damage their own table, so that's minor.
853 : : */
854 [ - + ]: 228991 : if (retries++ > 10000)
855 [ # # ]: 0 : elog(ERROR, "giving up after too many tries to overwrite row");
856 : :
857 : 228991 : INJECTION_POINT("inplace-before-pin", NULL);
858 : 228991 : scan = systable_beginscan(relation, indexId, indexOK, snapshot,
859 : : nkeys, unconstify(ScanKeyData *, key));
860 : 228991 : oldtup = systable_getnext(scan);
861 [ - + ]: 228991 : if (!HeapTupleIsValid(oldtup))
862 : : {
863 : 0 : systable_endscan(scan);
864 : 0 : *oldtupcopy = NULL;
865 : 0 : return;
866 : : }
867 : :
868 : 228991 : slot = scan->slot;
869 : : Assert(TTS_IS_BUFFERTUPLE(slot));
870 : 228991 : bslot = (BufferHeapTupleTableSlot *) slot;
871 [ + + ]: 228991 : } while (!heap_inplace_lock(scan->heap_rel,
872 : : bslot->base.tuple, bslot->buffer,
873 : : (void (*) (void *)) systable_endscan, scan));
874 : :
875 : 228973 : *oldtupcopy = heap_copytuple(oldtup);
876 : 228973 : *state = scan;
877 : : }
878 : :
879 : : /*
880 : : * systable_inplace_update_finish --- second phase of inplace update
881 : : *
882 : : * The tuple cannot change size, and therefore its header fields and null
883 : : * bitmap (if any) don't change either.
884 : : */
885 : : void
886 : 100774 : systable_inplace_update_finish(void *state, HeapTuple tuple)
887 : : {
888 : 100774 : SysScanDesc scan = (SysScanDesc) state;
889 : 100774 : Relation relation = scan->heap_rel;
890 : 100774 : TupleTableSlot *slot = scan->slot;
891 : 100774 : BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
892 : 100774 : HeapTuple oldtup = bslot->base.tuple;
893 : 100774 : Buffer buffer = bslot->buffer;
894 : :
895 : 100774 : heap_inplace_update_and_unlock(relation, oldtup, tuple, buffer);
896 : 100774 : systable_endscan(scan);
897 : 100774 : }
898 : :
899 : : /*
900 : : * systable_inplace_update_cancel --- abandon inplace update
901 : : *
902 : : * This is an alternative to making a no-op update.
903 : : */
904 : : void
905 : 128199 : systable_inplace_update_cancel(void *state)
906 : : {
907 : 128199 : SysScanDesc scan = (SysScanDesc) state;
908 : 128199 : Relation relation = scan->heap_rel;
909 : 128199 : TupleTableSlot *slot = scan->slot;
910 : 128199 : BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
911 : 128199 : HeapTuple oldtup = bslot->base.tuple;
912 : 128199 : Buffer buffer = bslot->buffer;
913 : :
914 : 128199 : heap_inplace_unlock(relation, oldtup, buffer);
915 : 128199 : systable_endscan(scan);
916 : 128199 : }
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