1 /*-------------------------------------------------------------------------
2 *
3 * execIndexing.c
4 * routines for inserting index tuples and enforcing unique and
5 * exclusive constraints.
6 *
7 * ExecInsertIndexTuples() is the main entry point. It's called after
8 * inserting a tuple to the heap, and it inserts corresponding index tuples
9 * into all indexes. At the same time, it enforces any unique and
10 * exclusion constraints:
11 *
12 * Unique Indexes
13 * --------------
14 *
15 * Enforcing a unique constraint is straightforward. When the index AM
16 * inserts the tuple to the index, it also checks that there are no
17 * conflicting tuples in the index already. It does so atomically, so that
18 * even if two backends try to insert the same key concurrently, only one
19 * of them will succeed. All the logic to ensure atomicity, and to wait
20 * for in-progress transactions to finish, is handled by the index AM.
21 *
22 * If a unique constraint is deferred, we request the index AM to not
23 * throw an error if a conflict is found. Instead, we make note that there
24 * was a conflict and return the list of indexes with conflicts to the
25 * caller. The caller must re-check them later, by calling index_insert()
26 * with the UNIQUE_CHECK_EXISTING option.
27 *
28 * Exclusion Constraints
29 * ---------------------
30 *
31 * Exclusion constraints are different from unique indexes in that when the
32 * tuple is inserted to the index, the index AM does not check for
33 * duplicate keys at the same time. After the insertion, we perform a
34 * separate scan on the index to check for conflicting tuples, and if one
35 * is found, we throw an error and the transaction is aborted. If the
36 * conflicting tuple's inserter or deleter is in-progress, we wait for it
37 * to finish first.
38 *
39 * There is a chance of deadlock, if two backends insert a tuple at the
40 * same time, and then perform the scan to check for conflicts. They will
41 * find each other's tuple, and both try to wait for each other. The
42 * deadlock detector will detect that, and abort one of the transactions.
43 * That's fairly harmless, as one of them was bound to abort with a
44 * "duplicate key error" anyway, although you get a different error
45 * message.
46 *
47 * If an exclusion constraint is deferred, we still perform the conflict
48 * checking scan immediately after inserting the index tuple. But instead
49 * of throwing an error if a conflict is found, we return that information
50 * to the caller. The caller must re-check them later by calling
51 * check_exclusion_constraint().
52 *
53 * Speculative insertion
54 * ---------------------
55 *
56 * Speculative insertion is a two-phase mechanism used to implement
57 * INSERT ... ON CONFLICT DO UPDATE/NOTHING. The tuple is first inserted
58 * to the heap and update the indexes as usual, but if a constraint is
59 * violated, we can still back out the insertion without aborting the whole
60 * transaction. In an INSERT ... ON CONFLICT statement, if a conflict is
61 * detected, the inserted tuple is backed out and the ON CONFLICT action is
62 * executed instead.
63 *
64 * Insertion to a unique index works as usual: the index AM checks for
65 * duplicate keys atomically with the insertion. But instead of throwing
66 * an error on a conflict, the speculatively inserted heap tuple is backed
67 * out.
68 *
69 * Exclusion constraints are slightly more complicated. As mentioned
70 * earlier, there is a risk of deadlock when two backends insert the same
71 * key concurrently. That was not a problem for regular insertions, when
72 * one of the transactions has to be aborted anyway, but with a speculative
73 * insertion we cannot let a deadlock happen, because we only want to back
74 * out the speculatively inserted tuple on conflict, not abort the whole
75 * transaction.
76 *
77 * When a backend detects that the speculative insertion conflicts with
78 * another in-progress tuple, it has two options:
79 *
80 * 1. back out the speculatively inserted tuple, then wait for the other
81 * transaction, and retry. Or,
82 * 2. wait for the other transaction, with the speculatively inserted tuple
83 * still in place.
84 *
85 * If two backends insert at the same time, and both try to wait for each
86 * other, they will deadlock. So option 2 is not acceptable. Option 1
87 * avoids the deadlock, but it is prone to a livelock instead. Both
88 * transactions will wake up immediately as the other transaction backs
89 * out. Then they both retry, and conflict with each other again, lather,
90 * rinse, repeat.
91 *
92 * To avoid the livelock, one of the backends must back out first, and then
93 * wait, while the other one waits without backing out. It doesn't matter
94 * which one backs out, so we employ an arbitrary rule that the transaction
95 * with the higher XID backs out.
96 *
97 *
98 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
99 * Portions Copyright (c) 1994, Regents of the University of California
100 *
101 *
102 * IDENTIFICATION
103 * src/backend/executor/execIndexing.c
104 *
105 *-------------------------------------------------------------------------
106 */
107 #include "postgres.h"
108
109 #include "access/relscan.h"
110 #include "access/xact.h"
111 #include "catalog/index.h"
112 #include "executor/executor.h"
113 #include "nodes/nodeFuncs.h"
114 #include "storage/lmgr.h"
115 #include "utils/tqual.h"
116
117 /* waitMode argument to check_exclusion_or_unique_constraint() */
118 typedef enum
119 {
120 CEOUC_WAIT,
121 CEOUC_NOWAIT,
122 CEOUC_LIVELOCK_PREVENTING_WAIT
123 } CEOUC_WAIT_MODE;
124
125 static bool check_exclusion_or_unique_constraint(Relation heap, Relation index,
126 IndexInfo *indexInfo,
127 ItemPointer tupleid,
128 Datum *values, bool *isnull,
129 EState *estate, bool newIndex,
130 CEOUC_WAIT_MODE waitMode,
131 bool errorOK,
132 ItemPointer conflictTid);
133
134 static bool index_recheck_constraint(Relation index, Oid *constr_procs,
135 Datum *existing_values, bool *existing_isnull,
136 Datum *new_values);
137
138 /* ----------------------------------------------------------------
139 * ExecOpenIndices
140 *
141 * Find the indices associated with a result relation, open them,
142 * and save information about them in the result ResultRelInfo.
143 *
144 * At entry, caller has already opened and locked
145 * resultRelInfo->ri_RelationDesc.
146 * ----------------------------------------------------------------
147 */
148 void
ExecOpenIndices(ResultRelInfo * resultRelInfo,bool speculative)149 ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative)
150 {
151 Relation resultRelation = resultRelInfo->ri_RelationDesc;
152 List *indexoidlist;
153 ListCell *l;
154 int len,
155 i;
156 RelationPtr relationDescs;
157 IndexInfo **indexInfoArray;
158
159 resultRelInfo->ri_NumIndices = 0;
160
161 /* fast path if no indexes */
162 if (!RelationGetForm(resultRelation)->relhasindex)
163 return;
164
165 /*
166 * Get cached list of index OIDs
167 */
168 indexoidlist = RelationGetIndexList(resultRelation);
169 len = list_length(indexoidlist);
170 if (len == 0)
171 return;
172
173 /*
174 * allocate space for result arrays
175 */
176 relationDescs = (RelationPtr) palloc(len * sizeof(Relation));
177 indexInfoArray = (IndexInfo **) palloc(len * sizeof(IndexInfo *));
178
179 resultRelInfo->ri_NumIndices = len;
180 resultRelInfo->ri_IndexRelationDescs = relationDescs;
181 resultRelInfo->ri_IndexRelationInfo = indexInfoArray;
182
183 /*
184 * For each index, open the index relation and save pg_index info. We
185 * acquire RowExclusiveLock, signifying we will update the index.
186 *
187 * Note: we do this even if the index is not IndexIsReady; it's not worth
188 * the trouble to optimize for the case where it isn't.
189 */
190 i = 0;
191 foreach(l, indexoidlist)
192 {
193 Oid indexOid = lfirst_oid(l);
194 Relation indexDesc;
195 IndexInfo *ii;
196
197 indexDesc = index_open(indexOid, RowExclusiveLock);
198
199 /* extract index key information from the index's pg_index info */
200 ii = BuildIndexInfo(indexDesc);
201
202 /*
203 * If the indexes are to be used for speculative insertion, add extra
204 * information required by unique index entries.
205 */
206 if (speculative && ii->ii_Unique)
207 BuildSpeculativeIndexInfo(indexDesc, ii);
208
209 relationDescs[i] = indexDesc;
210 indexInfoArray[i] = ii;
211 i++;
212 }
213
214 list_free(indexoidlist);
215 }
216
217 /* ----------------------------------------------------------------
218 * ExecCloseIndices
219 *
220 * Close the index relations stored in resultRelInfo
221 * ----------------------------------------------------------------
222 */
223 void
ExecCloseIndices(ResultRelInfo * resultRelInfo)224 ExecCloseIndices(ResultRelInfo *resultRelInfo)
225 {
226 int i;
227 int numIndices;
228 RelationPtr indexDescs;
229
230 numIndices = resultRelInfo->ri_NumIndices;
231 indexDescs = resultRelInfo->ri_IndexRelationDescs;
232
233 for (i = 0; i < numIndices; i++)
234 {
235 if (indexDescs[i] == NULL)
236 continue; /* shouldn't happen? */
237
238 /* Drop lock acquired by ExecOpenIndices */
239 index_close(indexDescs[i], RowExclusiveLock);
240 }
241
242 /*
243 * XXX should free indexInfo array here too? Currently we assume that
244 * such stuff will be cleaned up automatically in FreeExecutorState.
245 */
246 }
247
248 /* ----------------------------------------------------------------
249 * ExecInsertIndexTuples
250 *
251 * This routine takes care of inserting index tuples
252 * into all the relations indexing the result relation
253 * when a heap tuple is inserted into the result relation.
254 *
255 * Unique and exclusion constraints are enforced at the same
256 * time. This returns a list of index OIDs for any unique or
257 * exclusion constraints that are deferred and that had
258 * potential (unconfirmed) conflicts. (if noDupErr == true,
259 * the same is done for non-deferred constraints, but report
260 * if conflict was speculative or deferred conflict to caller)
261 *
262 * If 'arbiterIndexes' is nonempty, noDupErr applies only to
263 * those indexes. NIL means noDupErr applies to all indexes.
264 *
265 * CAUTION: this must not be called for a HOT update.
266 * We can't defend against that here for lack of info.
267 * Should we change the API to make it safer?
268 * ----------------------------------------------------------------
269 */
270 List *
ExecInsertIndexTuples(TupleTableSlot * slot,ItemPointer tupleid,EState * estate,bool noDupErr,bool * specConflict,List * arbiterIndexes)271 ExecInsertIndexTuples(TupleTableSlot *slot,
272 ItemPointer tupleid,
273 EState *estate,
274 bool noDupErr,
275 bool *specConflict,
276 List *arbiterIndexes)
277 {
278 List *result = NIL;
279 ResultRelInfo *resultRelInfo;
280 int i;
281 int numIndices;
282 RelationPtr relationDescs;
283 Relation heapRelation;
284 IndexInfo **indexInfoArray;
285 ExprContext *econtext;
286 Datum values[INDEX_MAX_KEYS];
287 bool isnull[INDEX_MAX_KEYS];
288
289 /*
290 * Get information from the result relation info structure.
291 */
292 resultRelInfo = estate->es_result_relation_info;
293 numIndices = resultRelInfo->ri_NumIndices;
294 relationDescs = resultRelInfo->ri_IndexRelationDescs;
295 indexInfoArray = resultRelInfo->ri_IndexRelationInfo;
296 heapRelation = resultRelInfo->ri_RelationDesc;
297
298 /*
299 * We will use the EState's per-tuple context for evaluating predicates
300 * and index expressions (creating it if it's not already there).
301 */
302 econtext = GetPerTupleExprContext(estate);
303
304 /* Arrange for econtext's scan tuple to be the tuple under test */
305 econtext->ecxt_scantuple = slot;
306
307 /*
308 * for each index, form and insert the index tuple
309 */
310 for (i = 0; i < numIndices; i++)
311 {
312 Relation indexRelation = relationDescs[i];
313 IndexInfo *indexInfo;
314 bool applyNoDupErr;
315 IndexUniqueCheck checkUnique;
316 bool satisfiesConstraint;
317
318 if (indexRelation == NULL)
319 continue;
320
321 indexInfo = indexInfoArray[i];
322
323 /* If the index is marked as read-only, ignore it */
324 if (!indexInfo->ii_ReadyForInserts)
325 continue;
326
327 /* Check for partial index */
328 if (indexInfo->ii_Predicate != NIL)
329 {
330 List *predicate;
331
332 /*
333 * If predicate state not set up yet, create it (in the estate's
334 * per-query context)
335 */
336 predicate = indexInfo->ii_PredicateState;
337 if (predicate == NIL)
338 {
339 predicate = (List *)
340 ExecPrepareExpr((Expr *) indexInfo->ii_Predicate,
341 estate);
342 indexInfo->ii_PredicateState = predicate;
343 }
344
345 /* Skip this index-update if the predicate isn't satisfied */
346 if (!ExecQual(predicate, econtext, false))
347 continue;
348 }
349
350 /*
351 * FormIndexDatum fills in its values and isnull parameters with the
352 * appropriate values for the column(s) of the index.
353 */
354 FormIndexDatum(indexInfo,
355 slot,
356 estate,
357 values,
358 isnull);
359
360 /* Check whether to apply noDupErr to this index */
361 applyNoDupErr = noDupErr &&
362 (arbiterIndexes == NIL ||
363 list_member_oid(arbiterIndexes,
364 indexRelation->rd_index->indexrelid));
365
366 /*
367 * The index AM does the actual insertion, plus uniqueness checking.
368 *
369 * For an immediate-mode unique index, we just tell the index AM to
370 * throw error if not unique.
371 *
372 * For a deferrable unique index, we tell the index AM to just detect
373 * possible non-uniqueness, and we add the index OID to the result
374 * list if further checking is needed.
375 *
376 * For a speculative insertion (used by INSERT ... ON CONFLICT), do
377 * the same as for a deferrable unique index.
378 */
379 if (!indexRelation->rd_index->indisunique)
380 checkUnique = UNIQUE_CHECK_NO;
381 else if (applyNoDupErr)
382 checkUnique = UNIQUE_CHECK_PARTIAL;
383 else if (indexRelation->rd_index->indimmediate)
384 checkUnique = UNIQUE_CHECK_YES;
385 else
386 checkUnique = UNIQUE_CHECK_PARTIAL;
387
388 satisfiesConstraint =
389 index_insert(indexRelation, /* index relation */
390 values, /* array of index Datums */
391 isnull, /* null flags */
392 tupleid, /* tid of heap tuple */
393 heapRelation, /* heap relation */
394 checkUnique); /* type of uniqueness check to do */
395
396 /*
397 * If the index has an associated exclusion constraint, check that.
398 * This is simpler than the process for uniqueness checks since we
399 * always insert first and then check. If the constraint is deferred,
400 * we check now anyway, but don't throw error on violation or wait for
401 * a conclusive outcome from a concurrent insertion; instead we'll
402 * queue a recheck event. Similarly, noDupErr callers (speculative
403 * inserters) will recheck later, and wait for a conclusive outcome
404 * then.
405 *
406 * An index for an exclusion constraint can't also be UNIQUE (not an
407 * essential property, we just don't allow it in the grammar), so no
408 * need to preserve the prior state of satisfiesConstraint.
409 */
410 if (indexInfo->ii_ExclusionOps != NULL)
411 {
412 bool violationOK;
413 CEOUC_WAIT_MODE waitMode;
414
415 if (applyNoDupErr)
416 {
417 violationOK = true;
418 waitMode = CEOUC_LIVELOCK_PREVENTING_WAIT;
419 }
420 else if (!indexRelation->rd_index->indimmediate)
421 {
422 violationOK = true;
423 waitMode = CEOUC_NOWAIT;
424 }
425 else
426 {
427 violationOK = false;
428 waitMode = CEOUC_WAIT;
429 }
430
431 satisfiesConstraint =
432 check_exclusion_or_unique_constraint(heapRelation,
433 indexRelation, indexInfo,
434 tupleid, values, isnull,
435 estate, false,
436 waitMode, violationOK, NULL);
437 }
438
439 if ((checkUnique == UNIQUE_CHECK_PARTIAL ||
440 indexInfo->ii_ExclusionOps != NULL) &&
441 !satisfiesConstraint)
442 {
443 /*
444 * The tuple potentially violates the uniqueness or exclusion
445 * constraint, so make a note of the index so that we can re-check
446 * it later. Speculative inserters are told if there was a
447 * speculative conflict, since that always requires a restart.
448 */
449 result = lappend_oid(result, RelationGetRelid(indexRelation));
450 if (indexRelation->rd_index->indimmediate && specConflict)
451 *specConflict = true;
452 }
453 }
454
455 return result;
456 }
457
458 /* ----------------------------------------------------------------
459 * ExecCheckIndexConstraints
460 *
461 * This routine checks if a tuple violates any unique or
462 * exclusion constraints. Returns true if there is no conflict.
463 * Otherwise returns false, and the TID of the conflicting
464 * tuple is returned in *conflictTid.
465 *
466 * If 'arbiterIndexes' is given, only those indexes are checked.
467 * NIL means all indexes.
468 *
469 * Note that this doesn't lock the values in any way, so it's
470 * possible that a conflicting tuple is inserted immediately
471 * after this returns. But this can be used for a pre-check
472 * before insertion.
473 * ----------------------------------------------------------------
474 */
475 bool
ExecCheckIndexConstraints(TupleTableSlot * slot,EState * estate,ItemPointer conflictTid,List * arbiterIndexes)476 ExecCheckIndexConstraints(TupleTableSlot *slot,
477 EState *estate, ItemPointer conflictTid,
478 List *arbiterIndexes)
479 {
480 ResultRelInfo *resultRelInfo;
481 int i;
482 int numIndices;
483 RelationPtr relationDescs;
484 Relation heapRelation;
485 IndexInfo **indexInfoArray;
486 ExprContext *econtext;
487 Datum values[INDEX_MAX_KEYS];
488 bool isnull[INDEX_MAX_KEYS];
489 ItemPointerData invalidItemPtr;
490 bool checkedIndex = false;
491
492 ItemPointerSetInvalid(conflictTid);
493 ItemPointerSetInvalid(&invalidItemPtr);
494
495 /*
496 * Get information from the result relation info structure.
497 */
498 resultRelInfo = estate->es_result_relation_info;
499 numIndices = resultRelInfo->ri_NumIndices;
500 relationDescs = resultRelInfo->ri_IndexRelationDescs;
501 indexInfoArray = resultRelInfo->ri_IndexRelationInfo;
502 heapRelation = resultRelInfo->ri_RelationDesc;
503
504 /*
505 * We will use the EState's per-tuple context for evaluating predicates
506 * and index expressions (creating it if it's not already there).
507 */
508 econtext = GetPerTupleExprContext(estate);
509
510 /* Arrange for econtext's scan tuple to be the tuple under test */
511 econtext->ecxt_scantuple = slot;
512
513 /*
514 * For each index, form index tuple and check if it satisfies the
515 * constraint.
516 */
517 for (i = 0; i < numIndices; i++)
518 {
519 Relation indexRelation = relationDescs[i];
520 IndexInfo *indexInfo;
521 bool satisfiesConstraint;
522
523 if (indexRelation == NULL)
524 continue;
525
526 indexInfo = indexInfoArray[i];
527
528 if (!indexInfo->ii_Unique && !indexInfo->ii_ExclusionOps)
529 continue;
530
531 /* If the index is marked as read-only, ignore it */
532 if (!indexInfo->ii_ReadyForInserts)
533 continue;
534
535 /* When specific arbiter indexes requested, only examine them */
536 if (arbiterIndexes != NIL &&
537 !list_member_oid(arbiterIndexes,
538 indexRelation->rd_index->indexrelid))
539 continue;
540
541 if (!indexRelation->rd_index->indimmediate)
542 ereport(ERROR,
543 (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
544 errmsg("ON CONFLICT does not support deferrable unique constraints/exclusion constraints as arbiters"),
545 errtableconstraint(heapRelation,
546 RelationGetRelationName(indexRelation))));
547
548 checkedIndex = true;
549
550 /* Check for partial index */
551 if (indexInfo->ii_Predicate != NIL)
552 {
553 List *predicate;
554
555 /*
556 * If predicate state not set up yet, create it (in the estate's
557 * per-query context)
558 */
559 predicate = indexInfo->ii_PredicateState;
560 if (predicate == NIL)
561 {
562 predicate = (List *)
563 ExecPrepareExpr((Expr *) indexInfo->ii_Predicate,
564 estate);
565 indexInfo->ii_PredicateState = predicate;
566 }
567
568 /* Skip this index-update if the predicate isn't satisfied */
569 if (!ExecQual(predicate, econtext, false))
570 continue;
571 }
572
573 /*
574 * FormIndexDatum fills in its values and isnull parameters with the
575 * appropriate values for the column(s) of the index.
576 */
577 FormIndexDatum(indexInfo,
578 slot,
579 estate,
580 values,
581 isnull);
582
583 satisfiesConstraint =
584 check_exclusion_or_unique_constraint(heapRelation, indexRelation,
585 indexInfo, &invalidItemPtr,
586 values, isnull, estate, false,
587 CEOUC_WAIT, true,
588 conflictTid);
589 if (!satisfiesConstraint)
590 return false;
591 }
592
593 if (arbiterIndexes != NIL && !checkedIndex)
594 elog(ERROR, "unexpected failure to find arbiter index");
595
596 return true;
597 }
598
599 /*
600 * Check for violation of an exclusion or unique constraint
601 *
602 * heap: the table containing the new tuple
603 * index: the index supporting the constraint
604 * indexInfo: info about the index, including the exclusion properties
605 * tupleid: heap TID of the new tuple we have just inserted (invalid if we
606 * haven't inserted a new tuple yet)
607 * values, isnull: the *index* column values computed for the new tuple
608 * estate: an EState we can do evaluation in
609 * newIndex: if true, we are trying to build a new index (this affects
610 * only the wording of error messages)
611 * waitMode: whether to wait for concurrent inserters/deleters
612 * violationOK: if true, don't throw error for violation
613 * conflictTid: if not-NULL, the TID of the conflicting tuple is returned here
614 *
615 * Returns true if OK, false if actual or potential violation
616 *
617 * 'waitMode' determines what happens if a conflict is detected with a tuple
618 * that was inserted or deleted by a transaction that's still running.
619 * CEOUC_WAIT means that we wait for the transaction to commit, before
620 * throwing an error or returning. CEOUC_NOWAIT means that we report the
621 * violation immediately; so the violation is only potential, and the caller
622 * must recheck sometime later. This behavior is convenient for deferred
623 * exclusion checks; we need not bother queuing a deferred event if there is
624 * definitely no conflict at insertion time.
625 *
626 * CEOUC_LIVELOCK_PREVENTING_WAIT is like CEOUC_NOWAIT, but we will sometimes
627 * wait anyway, to prevent livelocking if two transactions try inserting at
628 * the same time. This is used with speculative insertions, for INSERT ON
629 * CONFLICT statements. (See notes in file header)
630 *
631 * If violationOK is true, we just report the potential or actual violation to
632 * the caller by returning 'false'. Otherwise we throw a descriptive error
633 * message here. When violationOK is false, a false result is impossible.
634 *
635 * Note: The indexam is normally responsible for checking unique constraints,
636 * so this normally only needs to be used for exclusion constraints. But this
637 * function is also called when doing a "pre-check" for conflicts on a unique
638 * constraint, when doing speculative insertion. Caller may use the returned
639 * conflict TID to take further steps.
640 */
641 static bool
check_exclusion_or_unique_constraint(Relation heap,Relation index,IndexInfo * indexInfo,ItemPointer tupleid,Datum * values,bool * isnull,EState * estate,bool newIndex,CEOUC_WAIT_MODE waitMode,bool violationOK,ItemPointer conflictTid)642 check_exclusion_or_unique_constraint(Relation heap, Relation index,
643 IndexInfo *indexInfo,
644 ItemPointer tupleid,
645 Datum *values, bool *isnull,
646 EState *estate, bool newIndex,
647 CEOUC_WAIT_MODE waitMode,
648 bool violationOK,
649 ItemPointer conflictTid)
650 {
651 Oid *constr_procs;
652 uint16 *constr_strats;
653 Oid *index_collations = index->rd_indcollation;
654 int index_natts = index->rd_index->indnatts;
655 IndexScanDesc index_scan;
656 HeapTuple tup;
657 ScanKeyData scankeys[INDEX_MAX_KEYS];
658 SnapshotData DirtySnapshot;
659 int i;
660 bool conflict;
661 bool found_self;
662 ExprContext *econtext;
663 TupleTableSlot *existing_slot;
664 TupleTableSlot *save_scantuple;
665
666 if (indexInfo->ii_ExclusionOps)
667 {
668 constr_procs = indexInfo->ii_ExclusionProcs;
669 constr_strats = indexInfo->ii_ExclusionStrats;
670 }
671 else
672 {
673 constr_procs = indexInfo->ii_UniqueProcs;
674 constr_strats = indexInfo->ii_UniqueStrats;
675 }
676
677 /*
678 * If any of the input values are NULL, the constraint check is assumed to
679 * pass (i.e., we assume the operators are strict).
680 */
681 for (i = 0; i < index_natts; i++)
682 {
683 if (isnull[i])
684 return true;
685 }
686
687 /*
688 * Search the tuples that are in the index for any violations, including
689 * tuples that aren't visible yet.
690 */
691 InitDirtySnapshot(DirtySnapshot);
692
693 for (i = 0; i < index_natts; i++)
694 {
695 ScanKeyEntryInitialize(&scankeys[i],
696 0,
697 i + 1,
698 constr_strats[i],
699 InvalidOid,
700 index_collations[i],
701 constr_procs[i],
702 values[i]);
703 }
704
705 /*
706 * Need a TupleTableSlot to put existing tuples in.
707 *
708 * To use FormIndexDatum, we have to make the econtext's scantuple point
709 * to this slot. Be sure to save and restore caller's value for
710 * scantuple.
711 */
712 existing_slot = MakeSingleTupleTableSlot(RelationGetDescr(heap));
713
714 econtext = GetPerTupleExprContext(estate);
715 save_scantuple = econtext->ecxt_scantuple;
716 econtext->ecxt_scantuple = existing_slot;
717
718 /*
719 * May have to restart scan from this point if a potential conflict is
720 * found.
721 */
722 retry:
723 conflict = false;
724 found_self = false;
725 index_scan = index_beginscan(heap, index, &DirtySnapshot, index_natts, 0);
726 index_rescan(index_scan, scankeys, index_natts, NULL, 0);
727
728 while ((tup = index_getnext(index_scan,
729 ForwardScanDirection)) != NULL)
730 {
731 TransactionId xwait;
732 ItemPointerData ctid_wait;
733 XLTW_Oper reason_wait;
734 Datum existing_values[INDEX_MAX_KEYS];
735 bool existing_isnull[INDEX_MAX_KEYS];
736 char *error_new;
737 char *error_existing;
738
739 /*
740 * Ignore the entry for the tuple we're trying to check.
741 */
742 if (ItemPointerIsValid(tupleid) &&
743 ItemPointerEquals(tupleid, &tup->t_self))
744 {
745 if (found_self) /* should not happen */
746 elog(ERROR, "found self tuple multiple times in index \"%s\"",
747 RelationGetRelationName(index));
748 found_self = true;
749 continue;
750 }
751
752 /*
753 * Extract the index column values and isnull flags from the existing
754 * tuple.
755 */
756 ExecStoreTuple(tup, existing_slot, InvalidBuffer, false);
757 FormIndexDatum(indexInfo, existing_slot, estate,
758 existing_values, existing_isnull);
759
760 /* If lossy indexscan, must recheck the condition */
761 if (index_scan->xs_recheck)
762 {
763 if (!index_recheck_constraint(index,
764 constr_procs,
765 existing_values,
766 existing_isnull,
767 values))
768 continue; /* tuple doesn't actually match, so no
769 * conflict */
770 }
771
772 /*
773 * At this point we have either a conflict or a potential conflict.
774 *
775 * If an in-progress transaction is affecting the visibility of this
776 * tuple, we need to wait for it to complete and then recheck (unless
777 * the caller requested not to). For simplicity we do rechecking by
778 * just restarting the whole scan --- this case probably doesn't
779 * happen often enough to be worth trying harder, and anyway we don't
780 * want to hold any index internal locks while waiting.
781 */
782 xwait = TransactionIdIsValid(DirtySnapshot.xmin) ?
783 DirtySnapshot.xmin : DirtySnapshot.xmax;
784
785 if (TransactionIdIsValid(xwait) &&
786 (waitMode == CEOUC_WAIT ||
787 (waitMode == CEOUC_LIVELOCK_PREVENTING_WAIT &&
788 DirtySnapshot.speculativeToken &&
789 TransactionIdPrecedes(GetCurrentTransactionId(), xwait))))
790 {
791 ctid_wait = tup->t_data->t_ctid;
792 reason_wait = indexInfo->ii_ExclusionOps ?
793 XLTW_RecheckExclusionConstr : XLTW_InsertIndex;
794 index_endscan(index_scan);
795 if (DirtySnapshot.speculativeToken)
796 SpeculativeInsertionWait(DirtySnapshot.xmin,
797 DirtySnapshot.speculativeToken);
798 else
799 XactLockTableWait(xwait, heap, &ctid_wait, reason_wait);
800 goto retry;
801 }
802
803 /*
804 * We have a definite conflict (or a potential one, but the caller
805 * didn't want to wait). Return it to caller, or report it.
806 */
807 if (violationOK)
808 {
809 conflict = true;
810 if (conflictTid)
811 *conflictTid = tup->t_self;
812 break;
813 }
814
815 error_new = BuildIndexValueDescription(index, values, isnull);
816 error_existing = BuildIndexValueDescription(index, existing_values,
817 existing_isnull);
818 if (newIndex)
819 ereport(ERROR,
820 (errcode(ERRCODE_EXCLUSION_VIOLATION),
821 errmsg("could not create exclusion constraint \"%s\"",
822 RelationGetRelationName(index)),
823 error_new && error_existing ?
824 errdetail("Key %s conflicts with key %s.",
825 error_new, error_existing) :
826 errdetail("Key conflicts exist."),
827 errtableconstraint(heap,
828 RelationGetRelationName(index))));
829 else
830 ereport(ERROR,
831 (errcode(ERRCODE_EXCLUSION_VIOLATION),
832 errmsg("conflicting key value violates exclusion constraint \"%s\"",
833 RelationGetRelationName(index)),
834 error_new && error_existing ?
835 errdetail("Key %s conflicts with existing key %s.",
836 error_new, error_existing) :
837 errdetail("Key conflicts with existing key."),
838 errtableconstraint(heap,
839 RelationGetRelationName(index))));
840 }
841
842 index_endscan(index_scan);
843
844 /*
845 * Ordinarily, at this point the search should have found the originally
846 * inserted tuple (if any), unless we exited the loop early because of
847 * conflict. However, it is possible to define exclusion constraints for
848 * which that wouldn't be true --- for instance, if the operator is <>. So
849 * we no longer complain if found_self is still false.
850 */
851
852 econtext->ecxt_scantuple = save_scantuple;
853
854 ExecDropSingleTupleTableSlot(existing_slot);
855
856 return !conflict;
857 }
858
859 /*
860 * Check for violation of an exclusion constraint
861 *
862 * This is a dumbed down version of check_exclusion_or_unique_constraint
863 * for external callers. They don't need all the special modes.
864 */
865 void
check_exclusion_constraint(Relation heap,Relation index,IndexInfo * indexInfo,ItemPointer tupleid,Datum * values,bool * isnull,EState * estate,bool newIndex)866 check_exclusion_constraint(Relation heap, Relation index,
867 IndexInfo *indexInfo,
868 ItemPointer tupleid,
869 Datum *values, bool *isnull,
870 EState *estate, bool newIndex)
871 {
872 (void) check_exclusion_or_unique_constraint(heap, index, indexInfo, tupleid,
873 values, isnull,
874 estate, newIndex,
875 CEOUC_WAIT, false, NULL);
876 }
877
878 /*
879 * Check existing tuple's index values to see if it really matches the
880 * exclusion condition against the new_values. Returns true if conflict.
881 */
882 static bool
index_recheck_constraint(Relation index,Oid * constr_procs,Datum * existing_values,bool * existing_isnull,Datum * new_values)883 index_recheck_constraint(Relation index, Oid *constr_procs,
884 Datum *existing_values, bool *existing_isnull,
885 Datum *new_values)
886 {
887 int index_natts = index->rd_index->indnatts;
888 int i;
889
890 for (i = 0; i < index_natts; i++)
891 {
892 /* Assume the exclusion operators are strict */
893 if (existing_isnull[i])
894 return false;
895
896 if (!DatumGetBool(OidFunctionCall2Coll(constr_procs[i],
897 index->rd_indcollation[i],
898 existing_values[i],
899 new_values[i])))
900 return false;
901 }
902
903 return true;
904 }
905