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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 : 994991 : RelationGetIndexScan(Relation indexRelation, int nkeys, int norderbys)
81 : : {
82 : 994991 : IndexScanDesc scan;
83 : :
84 : 994991 : scan = palloc_object(IndexScanDescData);
85 : :
86 : 994991 : scan->heapRelation = NULL; /* may be set later */
87 : 994991 : scan->xs_heapfetch = NULL;
88 : 994991 : scan->indexRelation = indexRelation;
89 : 994991 : scan->xs_snapshot = InvalidSnapshot; /* caller must initialize this */
90 : 994991 : scan->numberOfKeys = nkeys;
91 : 994991 : scan->numberOfOrderBys = norderbys;
92 : :
93 : : /*
94 : : * We allocate key workspace here, but it won't get filled until amrescan.
95 : : */
96 [ + + ]: 994991 : if (nkeys > 0)
97 : 994252 : scan->keyData = palloc_array(ScanKeyData, nkeys);
98 : : else
99 : 739 : scan->keyData = NULL;
100 [ + + ]: 994991 : if (norderbys > 0)
101 : 23 : scan->orderByData = palloc_array(ScanKeyData, norderbys);
102 : : else
103 : 994968 : scan->orderByData = NULL;
104 : :
105 : 994991 : 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 : 994991 : scan->kill_prior_tuple = false;
118 : 994991 : scan->xactStartedInRecovery = TransactionStartedDuringRecovery();
119 : 994991 : scan->ignore_killed_tuples = !scan->xactStartedInRecovery;
120 : :
121 : 994991 : scan->opaque = NULL;
122 : 994991 : scan->instrument = NULL;
123 : :
124 : 994991 : scan->xs_itup = NULL;
125 : 994991 : scan->xs_itupdesc = NULL;
126 : 994991 : scan->xs_hitup = NULL;
127 : 994991 : scan->xs_hitupdesc = NULL;
128 : :
129 : 1989982 : return scan;
130 : 994991 : }
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 : 994736 : IndexScanEnd(IndexScanDesc scan)
146 : : {
147 [ + + ]: 994736 : if (scan->keyData != NULL)
148 : 994002 : pfree(scan->keyData);
149 [ + + ]: 994736 : if (scan->orderByData != NULL)
150 : 22 : pfree(scan->orderByData);
151 : :
152 : 994736 : pfree(scan);
153 : 994736 : }
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 : 125 : BuildIndexValueDescription(Relation indexRelation,
179 : : const Datum *values, const bool *isnull)
180 : : {
181 : 125 : StringInfoData buf;
182 : 125 : Form_pg_index idxrec;
183 : 125 : int indnkeyatts;
184 : 125 : int i;
185 : 125 : int keyno;
186 : 125 : Oid indexrelid = RelationGetRelid(indexRelation);
187 : 125 : Oid indrelid;
188 : 125 : AclResult aclresult;
189 : :
190 : 125 : 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 : 125 : idxrec = indexRelation->rd_index;
203 : 125 : indrelid = idxrec->indrelid;
204 [ + - ]: 125 : Assert(indexrelid == idxrec->indexrelid);
205 : :
206 : : /* RLS check- if RLS is enabled then we don't return anything. */
207 [ + + ]: 125 : if (check_enable_rls(indrelid, InvalidOid, true) == RLS_ENABLED)
208 : 2 : return NULL;
209 : :
210 : : /* Table-level SELECT is enough, if the user has it */
211 : 123 : aclresult = pg_class_aclcheck(indrelid, GetUserId(), ACL_SELECT);
212 [ + + ]: 123 : 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 [ + - ]: 4 : for (keyno = 0; keyno < indnkeyatts; keyno++)
219 : : {
220 : 4 : 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 [ + - + + ]: 4 : if (attnum == InvalidAttrNumber ||
229 : 4 : pg_attribute_aclcheck(indrelid, attnum, GetUserId(),
230 : 4 : ACL_SELECT) != ACLCHECK_OK)
231 : : {
232 : : /* No access, so clean up and return */
233 : 2 : return NULL;
234 : : }
235 [ + + ]: 4 : }
236 : 0 : }
237 : :
238 : 121 : initStringInfo(&buf);
239 : 121 : appendStringInfo(&buf, "(%s)=(",
240 : 121 : pg_get_indexdef_columns(indexrelid, true));
241 : :
242 [ + + ]: 291 : for (i = 0; i < indnkeyatts; i++)
243 : : {
244 : 170 : char *val;
245 : :
246 [ + + ]: 170 : if (isnull[i])
247 : 3 : val = "null";
248 : : else
249 : : {
250 : 167 : Oid foutoid;
251 : 167 : 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 : 167 : getTypeOutputInfo(indexRelation->rd_opcintype[i],
264 : : &foutoid, &typisvarlena);
265 : 167 : val = OidOutputFunctionCall(foutoid, values[i]);
266 : 167 : }
267 : :
268 [ + + ]: 170 : if (i > 0)
269 : 49 : appendStringInfoString(&buf, ", ");
270 : 170 : appendStringInfoString(&buf, val);
271 : 170 : }
272 : :
273 : 121 : appendStringInfoChar(&buf, ')');
274 : :
275 : 121 : return buf.data;
276 : 125 : }
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 : 0 : index_compute_xid_horizon_for_tuples(Relation irel,
296 : : Relation hrel,
297 : : Buffer ibuf,
298 : : OffsetNumber *itemnos,
299 : : int nitems)
300 : : {
301 : 0 : TM_IndexDeleteOp delstate;
302 : 0 : TransactionId snapshotConflictHorizon = InvalidTransactionId;
303 : 0 : Page ipage = BufferGetPage(ibuf);
304 : 0 : IndexTuple itup;
305 : :
306 [ # # ]: 0 : Assert(nitems > 0);
307 : :
308 : 0 : delstate.irel = irel;
309 : 0 : delstate.iblknum = BufferGetBlockNumber(ibuf);
310 : 0 : delstate.bottomup = false;
311 : 0 : delstate.bottomupfreespace = 0;
312 : 0 : delstate.ndeltids = 0;
313 : 0 : delstate.deltids = palloc_array(TM_IndexDelete, nitems);
314 : 0 : delstate.status = palloc_array(TM_IndexStatus, nitems);
315 : :
316 : : /* identify what the index tuples about to be deleted point to */
317 [ # # ]: 0 : for (int i = 0; i < nitems; i++)
318 : : {
319 : 0 : OffsetNumber offnum = itemnos[i];
320 : 0 : ItemId iitemid;
321 : :
322 : 0 : iitemid = PageGetItemId(ipage, offnum);
323 : 0 : itup = (IndexTuple) PageGetItem(ipage, iitemid);
324 : :
325 [ # # ]: 0 : Assert(ItemIdIsDead(iitemid));
326 : :
327 : 0 : ItemPointerCopy(&itup->t_tid, &delstate.deltids[i].tid);
328 : 0 : delstate.deltids[i].id = delstate.ndeltids;
329 : 0 : delstate.status[i].idxoffnum = offnum;
330 : 0 : delstate.status[i].knowndeletable = true; /* LP_DEAD-marked */
331 : 0 : delstate.status[i].promising = false; /* unused */
332 : 0 : delstate.status[i].freespace = 0; /* unused */
333 : :
334 : 0 : delstate.ndeltids++;
335 : 0 : }
336 : :
337 : : /* determine the actual xid horizon */
338 : 0 : snapshotConflictHorizon = table_index_delete_tuples(hrel, &delstate);
339 : :
340 : : /* assert tableam agrees that all items are deletable */
341 [ # # ]: 0 : Assert(delstate.ndeltids == nitems);
342 : :
343 : 0 : pfree(delstate.deltids);
344 : 0 : pfree(delstate.status);
345 : :
346 : 0 : return snapshotConflictHorizon;
347 : 0 : }
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 : 879795 : systable_beginscan(Relation heapRelation,
389 : : Oid indexId,
390 : : bool indexOK,
391 : : Snapshot snapshot,
392 : : int nkeys, ScanKey key)
393 : : {
394 : 879795 : SysScanDesc sysscan;
395 : 879795 : Relation irel;
396 : :
397 [ + + ]: 879795 : if (indexOK &&
398 [ + + + + ]: 873958 : !IgnoreSystemIndexes &&
399 : 872727 : !ReindexIsProcessingIndex(indexId))
400 : 871166 : irel = index_open(indexId, AccessShareLock);
401 : : else
402 : 8629 : irel = NULL;
403 : :
404 : 879795 : sysscan = palloc_object(SysScanDescData);
405 : :
406 : 879795 : sysscan->heap_rel = heapRelation;
407 : 879795 : sysscan->irel = irel;
408 : 879795 : sysscan->slot = table_slot_create(heapRelation, NULL);
409 : :
410 [ + + ]: 879795 : if (snapshot == NULL)
411 : : {
412 : 840119 : Oid relid = RelationGetRelid(heapRelation);
413 : :
414 : 840119 : snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
415 : 840119 : sysscan->snapshot = snapshot;
416 : 840119 : }
417 : : else
418 : : {
419 : : /* Caller is responsible for any snapshot. */
420 : 39676 : sysscan->snapshot = NULL;
421 : : }
422 : :
423 [ + + ]: 879795 : if (irel)
424 : : {
425 : 871166 : int i;
426 : 871166 : ScanKey idxkey;
427 : :
428 : 871166 : idxkey = palloc_array(ScanKeyData, nkeys);
429 : :
430 : : /* Convert attribute numbers to be index column numbers. */
431 [ + + ]: 2308407 : for (i = 0; i < nkeys; i++)
432 : : {
433 : 1437241 : int j;
434 : :
435 : 1437241 : memcpy(&idxkey[i], &key[i], sizeof(ScanKeyData));
436 : :
437 [ - + ]: 2096791 : for (j = 0; j < IndexRelationGetNumberOfAttributes(irel); j++)
438 : : {
439 [ + + ]: 2096791 : if (key[i].sk_attno == irel->rd_index->indkey.values[j])
440 : : {
441 : 1437241 : idxkey[i].sk_attno = j + 1;
442 : 1437241 : break;
443 : : }
444 : 659550 : }
445 [ + - ]: 1437241 : if (j == IndexRelationGetNumberOfAttributes(irel))
446 [ # # # # ]: 0 : elog(ERROR, "column is not in index");
447 : 1437241 : }
448 : :
449 : 1742332 : sysscan->iscan = index_beginscan(heapRelation, irel,
450 : 871166 : snapshot, NULL, nkeys, 0);
451 : 871166 : index_rescan(sysscan->iscan, idxkey, nkeys, NULL, 0);
452 : 871166 : sysscan->scan = NULL;
453 : :
454 : 871166 : pfree(idxkey);
455 : 871166 : }
456 : : else
457 : : {
458 : : /*
459 : : * We disallow synchronized scans when forced to use a heapscan on a
460 : : * catalog. In most cases the desired rows are near the front, so
461 : : * that the unpredictable start point of a syncscan is a serious
462 : : * disadvantage; and there are no compensating advantages, because
463 : : * it's unlikely that such scans will occur in parallel.
464 : : */
465 : 17258 : sysscan->scan = table_beginscan_strat(heapRelation, snapshot,
466 : 8629 : nkeys, key,
467 : : true, false);
468 : 8629 : sysscan->iscan = NULL;
469 : : }
470 : :
471 : : /*
472 : : * If CheckXidAlive is set then set a flag to indicate that system table
473 : : * scan is in-progress. See detailed comments in xact.c where these
474 : : * variables are declared.
475 : : */
476 [ + - ]: 879795 : if (TransactionIdIsValid(CheckXidAlive))
477 : 0 : bsysscan = true;
478 : :
479 : 1759590 : return sysscan;
480 : 879795 : }
481 : :
482 : : /*
483 : : * HandleConcurrentAbort - Handle concurrent abort of the CheckXidAlive.
484 : : *
485 : : * Error out, if CheckXidAlive is aborted. We can't directly use
486 : : * TransactionIdDidAbort as after crash such transaction might not have been
487 : : * marked as aborted. See detailed comments in xact.c where the variable
488 : : * is declared.
489 : : */
490 : : static inline void
491 : 1961718 : HandleConcurrentAbort(void)
492 : : {
493 [ - + ]: 1961718 : if (TransactionIdIsValid(CheckXidAlive) &&
494 [ # # # # ]: 0 : !TransactionIdIsInProgress(CheckXidAlive) &&
495 : 0 : !TransactionIdDidCommit(CheckXidAlive))
496 [ # # # # ]: 0 : ereport(ERROR,
497 : : (errcode(ERRCODE_TRANSACTION_ROLLBACK),
498 : : errmsg("transaction aborted during system catalog scan")));
499 : 1961718 : }
500 : :
501 : : /*
502 : : * systable_getnext --- get next tuple in a heap-or-index scan
503 : : *
504 : : * Returns NULL if no more tuples available.
505 : : *
506 : : * Note that returned tuple is a reference to data in a disk buffer;
507 : : * it must not be modified, and should be presumed inaccessible after
508 : : * next getnext() or endscan() call.
509 : : *
510 : : * XXX: It'd probably make sense to offer a slot based interface, at least
511 : : * optionally.
512 : : */
513 : : HeapTuple
514 : 1927508 : systable_getnext(SysScanDesc sysscan)
515 : : {
516 : 1927508 : HeapTuple htup = NULL;
517 : :
518 [ + + ]: 1927508 : if (sysscan->irel)
519 : : {
520 [ + + ]: 1682129 : if (index_getnext_slot(sysscan->iscan, ForwardScanDirection, sysscan->slot))
521 : : {
522 : 1229654 : bool shouldFree;
523 : :
524 : 1229654 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
525 [ + - ]: 1229654 : Assert(!shouldFree);
526 : :
527 : : /*
528 : : * We currently don't need to support lossy index operators for
529 : : * any system catalog scan. It could be done here, using the scan
530 : : * keys to drive the operator calls, if we arranged to save the
531 : : * heap attnums during systable_beginscan(); this is practical
532 : : * because we still wouldn't need to support indexes on
533 : : * expressions.
534 : : */
535 [ + - ]: 1229654 : if (sysscan->iscan->xs_recheck)
536 [ # # # # ]: 0 : elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
537 : 1229654 : }
538 : 1682129 : }
539 : : else
540 : : {
541 [ + + ]: 245379 : if (table_scan_getnextslot(sysscan->scan, ForwardScanDirection, sysscan->slot))
542 : : {
543 : 242008 : bool shouldFree;
544 : :
545 : 242008 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, &shouldFree);
546 [ + - ]: 242008 : Assert(!shouldFree);
547 : 242008 : }
548 : : }
549 : :
550 : : /*
551 : : * Handle the concurrent abort while fetching the catalog tuple during
552 : : * logical streaming of a transaction.
553 : : */
554 : 1927508 : HandleConcurrentAbort();
555 : :
556 : 3855016 : return htup;
557 : 1927508 : }
558 : :
559 : : /*
560 : : * systable_recheck_tuple --- recheck visibility of most-recently-fetched tuple
561 : : *
562 : : * In particular, determine if this tuple would be visible to a catalog scan
563 : : * that started now. We don't handle the case of a non-MVCC scan snapshot,
564 : : * because no caller needs that yet.
565 : : *
566 : : * This is useful to test whether an object was deleted while we waited to
567 : : * acquire lock on it.
568 : : *
569 : : * Note: we don't actually *need* the tuple to be passed in, but it's a
570 : : * good crosscheck that the caller is interested in the right tuple.
571 : : */
572 : : bool
573 : 27072 : systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup)
574 : : {
575 : 27072 : Snapshot freshsnap;
576 : 27072 : bool result;
577 : :
578 [ + - ]: 27072 : Assert(tup == ExecFetchSlotHeapTuple(sysscan->slot, false, NULL));
579 : :
580 : 27072 : freshsnap = GetCatalogSnapshot(RelationGetRelid(sysscan->heap_rel));
581 : 27072 : freshsnap = RegisterSnapshot(freshsnap);
582 : :
583 : 54144 : result = table_tuple_satisfies_snapshot(sysscan->heap_rel,
584 : 27072 : sysscan->slot,
585 : 27072 : freshsnap);
586 : 27072 : UnregisterSnapshot(freshsnap);
587 : :
588 : : /*
589 : : * Handle the concurrent abort while fetching the catalog tuple during
590 : : * logical streaming of a transaction.
591 : : */
592 : 27072 : HandleConcurrentAbort();
593 : :
594 : 54144 : return result;
595 : 27072 : }
596 : :
597 : : /*
598 : : * systable_endscan --- close scan, release resources
599 : : *
600 : : * Note that it's still up to the caller to close the heap relation.
601 : : */
602 : : void
603 : 879671 : systable_endscan(SysScanDesc sysscan)
604 : : {
605 [ - + ]: 879671 : if (sysscan->slot)
606 : : {
607 : 879671 : ExecDropSingleTupleTableSlot(sysscan->slot);
608 : 879671 : sysscan->slot = NULL;
609 : 879671 : }
610 : :
611 [ + + ]: 879671 : if (sysscan->irel)
612 : : {
613 : 871043 : index_endscan(sysscan->iscan);
614 : 871043 : index_close(sysscan->irel, AccessShareLock);
615 : 871043 : }
616 : : else
617 : 8628 : table_endscan(sysscan->scan);
618 : :
619 [ + + ]: 879671 : if (sysscan->snapshot)
620 : 839995 : UnregisterSnapshot(sysscan->snapshot);
621 : :
622 : : /*
623 : : * Reset the bsysscan flag at the end of the systable scan. See detailed
624 : : * comments in xact.c where these variables are declared.
625 : : */
626 [ + - ]: 879671 : if (TransactionIdIsValid(CheckXidAlive))
627 : 0 : bsysscan = false;
628 : :
629 : 879671 : pfree(sysscan);
630 : 879671 : }
631 : :
632 : :
633 : : /*
634 : : * systable_beginscan_ordered --- set up for ordered catalog scan
635 : : *
636 : : * These routines have essentially the same API as systable_beginscan etc,
637 : : * except that they guarantee to return multiple matching tuples in
638 : : * index order. Also, for largely historical reasons, the index to use
639 : : * is opened and locked by the caller, not here.
640 : : *
641 : : * Currently we do not support non-index-based scans here. (In principle
642 : : * we could do a heapscan and sort, but the uses are in places that
643 : : * probably don't need to still work with corrupted catalog indexes.)
644 : : * For the moment, therefore, these functions are merely the thinest of
645 : : * wrappers around index_beginscan/index_getnext_slot. The main reason for
646 : : * their existence is to centralize possible future support of lossy operators
647 : : * in catalog scans.
648 : : */
649 : : SysScanDesc
650 : 1742 : systable_beginscan_ordered(Relation heapRelation,
651 : : Relation indexRelation,
652 : : Snapshot snapshot,
653 : : int nkeys, ScanKey key)
654 : : {
655 : 1742 : SysScanDesc sysscan;
656 : 1742 : int i;
657 : 1742 : ScanKey idxkey;
658 : :
659 : : /* REINDEX can probably be a hard error here ... */
660 [ + - ]: 1742 : if (ReindexIsProcessingIndex(RelationGetRelid(indexRelation)))
661 [ # # # # ]: 0 : ereport(ERROR,
662 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
663 : : errmsg("cannot access index \"%s\" while it is being reindexed",
664 : : RelationGetRelationName(indexRelation))));
665 : : /* ... but we only throw a warning about violating IgnoreSystemIndexes */
666 [ + - ]: 1742 : if (IgnoreSystemIndexes)
667 [ # # # # ]: 0 : elog(WARNING, "using index \"%s\" despite IgnoreSystemIndexes",
668 : : RelationGetRelationName(indexRelation));
669 : :
670 : 1742 : sysscan = palloc_object(SysScanDescData);
671 : :
672 : 1742 : sysscan->heap_rel = heapRelation;
673 : 1742 : sysscan->irel = indexRelation;
674 : 1742 : sysscan->slot = table_slot_create(heapRelation, NULL);
675 : :
676 [ + + ]: 1742 : if (snapshot == NULL)
677 : : {
678 : 635 : Oid relid = RelationGetRelid(heapRelation);
679 : :
680 : 635 : snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
681 : 635 : sysscan->snapshot = snapshot;
682 : 635 : }
683 : : else
684 : : {
685 : : /* Caller is responsible for any snapshot. */
686 : 1107 : sysscan->snapshot = NULL;
687 : : }
688 : :
689 : 1742 : idxkey = palloc_array(ScanKeyData, nkeys);
690 : :
691 : : /* Convert attribute numbers to be index column numbers. */
692 [ + + ]: 3629 : for (i = 0; i < nkeys; i++)
693 : : {
694 : 1887 : int j;
695 : :
696 : 1887 : memcpy(&idxkey[i], &key[i], sizeof(ScanKeyData));
697 : :
698 [ - + ]: 2359 : for (j = 0; j < IndexRelationGetNumberOfAttributes(indexRelation); j++)
699 : : {
700 [ + + ]: 2359 : if (key[i].sk_attno == indexRelation->rd_index->indkey.values[j])
701 : : {
702 : 1887 : idxkey[i].sk_attno = j + 1;
703 : 1887 : break;
704 : : }
705 : 472 : }
706 [ + - ]: 1887 : if (j == IndexRelationGetNumberOfAttributes(indexRelation))
707 [ # # # # ]: 0 : elog(ERROR, "column is not in index");
708 : 1887 : }
709 : :
710 : 3484 : sysscan->iscan = index_beginscan(heapRelation, indexRelation,
711 : 1742 : snapshot, NULL, nkeys, 0);
712 : 1742 : index_rescan(sysscan->iscan, idxkey, nkeys, NULL, 0);
713 : 1742 : sysscan->scan = NULL;
714 : :
715 : 1742 : pfree(idxkey);
716 : :
717 : : /*
718 : : * If CheckXidAlive is set then set a flag to indicate that system table
719 : : * scan is in-progress. See detailed comments in xact.c where these
720 : : * variables are declared.
721 : : */
722 [ + - ]: 1742 : if (TransactionIdIsValid(CheckXidAlive))
723 : 0 : bsysscan = true;
724 : :
725 : 3484 : return sysscan;
726 : 1742 : }
727 : :
728 : : /*
729 : : * systable_getnext_ordered --- get next tuple in an ordered catalog scan
730 : : */
731 : : HeapTuple
732 : 7138 : systable_getnext_ordered(SysScanDesc sysscan, ScanDirection direction)
733 : : {
734 : 7138 : HeapTuple htup = NULL;
735 : :
736 [ + - ]: 7138 : Assert(sysscan->irel);
737 [ + + ]: 7138 : if (index_getnext_slot(sysscan->iscan, direction, sysscan->slot))
738 : 5601 : htup = ExecFetchSlotHeapTuple(sysscan->slot, false, NULL);
739 : :
740 : : /* See notes in systable_getnext */
741 [ + + + - ]: 7138 : if (htup && sysscan->iscan->xs_recheck)
742 [ # # # # ]: 0 : elog(ERROR, "system catalog scans with lossy index conditions are not implemented");
743 : :
744 : : /*
745 : : * Handle the concurrent abort while fetching the catalog tuple during
746 : : * logical streaming of a transaction.
747 : : */
748 : 7138 : HandleConcurrentAbort();
749 : :
750 : 14276 : return htup;
751 : 7138 : }
752 : :
753 : : /*
754 : : * systable_endscan_ordered --- close scan, release resources
755 : : */
756 : : void
757 : 1740 : systable_endscan_ordered(SysScanDesc sysscan)
758 : : {
759 [ - + ]: 1740 : if (sysscan->slot)
760 : : {
761 : 1740 : ExecDropSingleTupleTableSlot(sysscan->slot);
762 : 1740 : sysscan->slot = NULL;
763 : 1740 : }
764 : :
765 [ + - ]: 1740 : Assert(sysscan->irel);
766 : 1740 : index_endscan(sysscan->iscan);
767 [ + + ]: 1740 : if (sysscan->snapshot)
768 : 633 : UnregisterSnapshot(sysscan->snapshot);
769 : :
770 : : /*
771 : : * Reset the bsysscan flag at the end of the systable scan. See detailed
772 : : * comments in xact.c where these variables are declared.
773 : : */
774 [ + - ]: 1740 : if (TransactionIdIsValid(CheckXidAlive))
775 : 0 : bsysscan = false;
776 : :
777 : 1740 : pfree(sysscan);
778 : 1740 : }
779 : :
780 : : /*
781 : : * systable_inplace_update_begin --- update a row "in place" (overwrite it)
782 : : *
783 : : * Overwriting violates both MVCC and transactional safety, so the uses of
784 : : * this function in Postgres are extremely limited. This makes no effort to
785 : : * support updating cache key columns or other indexed columns. Nonetheless
786 : : * we find some places to use it. See README.tuplock section "Locking to
787 : : * write inplace-updated tables" and later sections for expectations of
788 : : * readers and writers of a table that gets inplace updates. Standard flow:
789 : : *
790 : : * ... [any slow preparation not requiring oldtup] ...
791 : : * systable_inplace_update_begin([...], &tup, &inplace_state);
792 : : * if (!HeapTupleIsValid(tup))
793 : : * elog(ERROR, [...]);
794 : : * ... [buffer is exclusive-locked; mutate "tup"] ...
795 : : * if (dirty)
796 : : * systable_inplace_update_finish(inplace_state, tup);
797 : : * else
798 : : * systable_inplace_update_cancel(inplace_state);
799 : : *
800 : : * The first several params duplicate the systable_beginscan() param list.
801 : : * "oldtupcopy" is an output parameter, assigned NULL if the key ceases to
802 : : * find a live tuple. (In PROC_IN_VACUUM, that is a low-probability transient
803 : : * condition.) If "oldtupcopy" gets non-NULL, you must pass output parameter
804 : : * "state" to systable_inplace_update_finish() or
805 : : * systable_inplace_update_cancel().
806 : : */
807 : : void
808 : 10566 : systable_inplace_update_begin(Relation relation,
809 : : Oid indexId,
810 : : bool indexOK,
811 : : Snapshot snapshot,
812 : : int nkeys, const ScanKeyData *key,
813 : : HeapTuple *oldtupcopy,
814 : : void **state)
815 : : {
816 : 10566 : int retries = 0;
817 : 10566 : SysScanDesc scan;
818 : 10566 : HeapTuple oldtup;
819 : 10566 : BufferHeapTupleTableSlot *bslot;
820 : :
821 : : /*
822 : : * For now, we don't allow parallel updates. Unlike a regular update,
823 : : * this should never create a combo CID, so it might be possible to relax
824 : : * this restriction, but not without more thought and testing. It's not
825 : : * clear that it would be useful, anyway.
826 : : */
827 [ + - ]: 10566 : if (IsInParallelMode())
828 [ # # # # ]: 0 : ereport(ERROR,
829 : : (errcode(ERRCODE_INVALID_TRANSACTION_STATE),
830 : : errmsg("cannot update tuples during a parallel operation")));
831 : :
832 : : /*
833 : : * Accept a snapshot argument, for symmetry, but this function advances
834 : : * its snapshot as needed to reach the tail of the updated tuple chain.
835 : : */
836 [ + - ]: 10566 : Assert(snapshot == NULL);
837 : :
838 [ - + # # ]: 10566 : Assert(IsInplaceUpdateRelation(relation) || !IsSystemRelation(relation));
839 : :
840 : : /* Loop for an exclusive-locked buffer of a non-updated tuple. */
841 : 10566 : do
842 : : {
843 : 10566 : TupleTableSlot *slot;
844 : :
845 [ + - ]: 10566 : CHECK_FOR_INTERRUPTS();
846 : :
847 : : /*
848 : : * Processes issuing heap_update (e.g. GRANT) at maximum speed could
849 : : * drive us to this error. A hostile table owner has stronger ways to
850 : : * damage their own table, so that's minor.
851 : : */
852 [ + - ]: 10566 : if (retries++ > 10000)
853 [ # # # # ]: 0 : elog(ERROR, "giving up after too many tries to overwrite row");
854 : :
855 : : INJECTION_POINT("inplace-before-pin", NULL);
856 : 21132 : scan = systable_beginscan(relation, indexId, indexOK, snapshot,
857 : 10566 : nkeys, unconstify(ScanKeyData *, key));
858 : 10566 : oldtup = systable_getnext(scan);
859 [ + - ]: 10566 : if (!HeapTupleIsValid(oldtup))
860 : : {
861 : 0 : systable_endscan(scan);
862 : 0 : *oldtupcopy = NULL;
863 : 0 : return;
864 : : }
865 : :
866 : 10566 : slot = scan->slot;
867 [ - + ]: 10566 : Assert(TTS_IS_BUFFERTUPLE(slot));
868 : 10566 : bslot = (BufferHeapTupleTableSlot *) slot;
869 [ - + - + : 10566 : } while (!heap_inplace_lock(scan->heap_rel,
- + ]
870 : 10566 : bslot->base.tuple, bslot->buffer,
871 : 10566 : (void (*) (void *)) systable_endscan, scan));
872 : :
873 : 10566 : *oldtupcopy = heap_copytuple(oldtup);
874 : 10566 : *state = scan;
875 [ - + ]: 10566 : }
876 : :
877 : : /*
878 : : * systable_inplace_update_finish --- second phase of inplace update
879 : : *
880 : : * The tuple cannot change size, and therefore its header fields and null
881 : : * bitmap (if any) don't change either.
882 : : */
883 : : void
884 : 7953 : systable_inplace_update_finish(void *state, HeapTuple tuple)
885 : : {
886 : 7953 : SysScanDesc scan = (SysScanDesc) state;
887 : 7953 : Relation relation = scan->heap_rel;
888 : 7953 : TupleTableSlot *slot = scan->slot;
889 : 7953 : BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
890 : 7953 : HeapTuple oldtup = bslot->base.tuple;
891 : 7953 : Buffer buffer = bslot->buffer;
892 : :
893 : 7953 : heap_inplace_update_and_unlock(relation, oldtup, tuple, buffer);
894 : 7953 : systable_endscan(scan);
895 : 7953 : }
896 : :
897 : : /*
898 : : * systable_inplace_update_cancel --- abandon inplace update
899 : : *
900 : : * This is an alternative to making a no-op update.
901 : : */
902 : : void
903 : 2613 : systable_inplace_update_cancel(void *state)
904 : : {
905 : 2613 : SysScanDesc scan = (SysScanDesc) state;
906 : 2613 : Relation relation = scan->heap_rel;
907 : 2613 : TupleTableSlot *slot = scan->slot;
908 : 2613 : BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
909 : 2613 : HeapTuple oldtup = bslot->base.tuple;
910 : 2613 : Buffer buffer = bslot->buffer;
911 : :
912 : 2613 : heap_inplace_unlock(relation, oldtup, buffer);
913 : 2613 : systable_endscan(scan);
914 : 2613 : }
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