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Diffstat (limited to 'src/backend/executor/execIndexing.c')
| -rw-r--r-- | src/backend/executor/execIndexing.c | 1077 |
1 files changed, 1077 insertions, 0 deletions
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c new file mode 100644 index 0000000..6a8735e --- /dev/null +++ b/src/backend/executor/execIndexing.c @@ -0,0 +1,1077 @@ +/*------------------------------------------------------------------------- + * + * execIndexing.c + * routines for inserting index tuples and enforcing unique and + * exclusion constraints. + * + * ExecInsertIndexTuples() is the main entry point. It's called after + * inserting a tuple to the heap, and it inserts corresponding index tuples + * into all indexes. At the same time, it enforces any unique and + * exclusion constraints: + * + * Unique Indexes + * -------------- + * + * Enforcing a unique constraint is straightforward. When the index AM + * inserts the tuple to the index, it also checks that there are no + * conflicting tuples in the index already. It does so atomically, so that + * even if two backends try to insert the same key concurrently, only one + * of them will succeed. All the logic to ensure atomicity, and to wait + * for in-progress transactions to finish, is handled by the index AM. + * + * If a unique constraint is deferred, we request the index AM to not + * throw an error if a conflict is found. Instead, we make note that there + * was a conflict and return the list of indexes with conflicts to the + * caller. The caller must re-check them later, by calling index_insert() + * with the UNIQUE_CHECK_EXISTING option. + * + * Exclusion Constraints + * --------------------- + * + * Exclusion constraints are different from unique indexes in that when the + * tuple is inserted to the index, the index AM does not check for + * duplicate keys at the same time. After the insertion, we perform a + * separate scan on the index to check for conflicting tuples, and if one + * is found, we throw an error and the transaction is aborted. If the + * conflicting tuple's inserter or deleter is in-progress, we wait for it + * to finish first. + * + * There is a chance of deadlock, if two backends insert a tuple at the + * same time, and then perform the scan to check for conflicts. They will + * find each other's tuple, and both try to wait for each other. The + * deadlock detector will detect that, and abort one of the transactions. + * That's fairly harmless, as one of them was bound to abort with a + * "duplicate key error" anyway, although you get a different error + * message. + * + * If an exclusion constraint is deferred, we still perform the conflict + * checking scan immediately after inserting the index tuple. But instead + * of throwing an error if a conflict is found, we return that information + * to the caller. The caller must re-check them later by calling + * check_exclusion_constraint(). + * + * Speculative insertion + * --------------------- + * + * Speculative insertion is a two-phase mechanism used to implement + * INSERT ... ON CONFLICT DO UPDATE/NOTHING. The tuple is first inserted + * to the heap and update the indexes as usual, but if a constraint is + * violated, we can still back out the insertion without aborting the whole + * transaction. In an INSERT ... ON CONFLICT statement, if a conflict is + * detected, the inserted tuple is backed out and the ON CONFLICT action is + * executed instead. + * + * Insertion to a unique index works as usual: the index AM checks for + * duplicate keys atomically with the insertion. But instead of throwing + * an error on a conflict, the speculatively inserted heap tuple is backed + * out. + * + * Exclusion constraints are slightly more complicated. As mentioned + * earlier, there is a risk of deadlock when two backends insert the same + * key concurrently. That was not a problem for regular insertions, when + * one of the transactions has to be aborted anyway, but with a speculative + * insertion we cannot let a deadlock happen, because we only want to back + * out the speculatively inserted tuple on conflict, not abort the whole + * transaction. + * + * When a backend detects that the speculative insertion conflicts with + * another in-progress tuple, it has two options: + * + * 1. back out the speculatively inserted tuple, then wait for the other + * transaction, and retry. Or, + * 2. wait for the other transaction, with the speculatively inserted tuple + * still in place. + * + * If two backends insert at the same time, and both try to wait for each + * other, they will deadlock. So option 2 is not acceptable. Option 1 + * avoids the deadlock, but it is prone to a livelock instead. Both + * transactions will wake up immediately as the other transaction backs + * out. Then they both retry, and conflict with each other again, lather, + * rinse, repeat. + * + * To avoid the livelock, one of the backends must back out first, and then + * wait, while the other one waits without backing out. It doesn't matter + * which one backs out, so we employ an arbitrary rule that the transaction + * with the higher XID backs out. + * + * + * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/executor/execIndexing.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "access/genam.h" +#include "access/relscan.h" +#include "access/tableam.h" +#include "access/xact.h" +#include "catalog/index.h" +#include "executor/executor.h" +#include "nodes/nodeFuncs.h" +#include "storage/lmgr.h" +#include "utils/snapmgr.h" + +/* waitMode argument to check_exclusion_or_unique_constraint() */ +typedef enum +{ + CEOUC_WAIT, + CEOUC_NOWAIT, + CEOUC_LIVELOCK_PREVENTING_WAIT +} CEOUC_WAIT_MODE; + +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 errorOK, + ItemPointer conflictTid); + +static bool index_recheck_constraint(Relation index, Oid *constr_procs, + Datum *existing_values, bool *existing_isnull, + Datum *new_values); +static bool index_unchanged_by_update(ResultRelInfo *resultRelInfo, + EState *estate, IndexInfo *indexInfo, + Relation indexRelation); +static bool index_expression_changed_walker(Node *node, + Bitmapset *allUpdatedCols); + +/* ---------------------------------------------------------------- + * ExecOpenIndices + * + * Find the indices associated with a result relation, open them, + * and save information about them in the result ResultRelInfo. + * + * At entry, caller has already opened and locked + * resultRelInfo->ri_RelationDesc. + * ---------------------------------------------------------------- + */ +void +ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative) +{ + Relation resultRelation = resultRelInfo->ri_RelationDesc; + List *indexoidlist; + ListCell *l; + int len, + i; + RelationPtr relationDescs; + IndexInfo **indexInfoArray; + + resultRelInfo->ri_NumIndices = 0; + + /* fast path if no indexes */ + if (!RelationGetForm(resultRelation)->relhasindex) + return; + + /* + * Get cached list of index OIDs + */ + indexoidlist = RelationGetIndexList(resultRelation); + len = list_length(indexoidlist); + if (len == 0) + return; + + /* + * allocate space for result arrays + */ + relationDescs = (RelationPtr) palloc(len * sizeof(Relation)); + indexInfoArray = (IndexInfo **) palloc(len * sizeof(IndexInfo *)); + + resultRelInfo->ri_NumIndices = len; + resultRelInfo->ri_IndexRelationDescs = relationDescs; + resultRelInfo->ri_IndexRelationInfo = indexInfoArray; + + /* + * For each index, open the index relation and save pg_index info. We + * acquire RowExclusiveLock, signifying we will update the index. + * + * Note: we do this even if the index is not indisready; it's not worth + * the trouble to optimize for the case where it isn't. + */ + i = 0; + foreach(l, indexoidlist) + { + Oid indexOid = lfirst_oid(l); + Relation indexDesc; + IndexInfo *ii; + + indexDesc = index_open(indexOid, RowExclusiveLock); + + /* extract index key information from the index's pg_index info */ + ii = BuildIndexInfo(indexDesc); + + /* + * If the indexes are to be used for speculative insertion, add extra + * information required by unique index entries. + */ + if (speculative && ii->ii_Unique) + BuildSpeculativeIndexInfo(indexDesc, ii); + + relationDescs[i] = indexDesc; + indexInfoArray[i] = ii; + i++; + } + + list_free(indexoidlist); +} + +/* ---------------------------------------------------------------- + * ExecCloseIndices + * + * Close the index relations stored in resultRelInfo + * ---------------------------------------------------------------- + */ +void +ExecCloseIndices(ResultRelInfo *resultRelInfo) +{ + int i; + int numIndices; + RelationPtr indexDescs; + + numIndices = resultRelInfo->ri_NumIndices; + indexDescs = resultRelInfo->ri_IndexRelationDescs; + + for (i = 0; i < numIndices; i++) + { + if (indexDescs[i] == NULL) + continue; /* shouldn't happen? */ + + /* Drop lock acquired by ExecOpenIndices */ + index_close(indexDescs[i], RowExclusiveLock); + } + + /* + * XXX should free indexInfo array here too? Currently we assume that + * such stuff will be cleaned up automatically in FreeExecutorState. + */ +} + +/* ---------------------------------------------------------------- + * ExecInsertIndexTuples + * + * This routine takes care of inserting index tuples + * into all the relations indexing the result relation + * when a heap tuple is inserted into the result relation. + * + * When 'update' is true, executor is performing an UPDATE + * that could not use an optimization like heapam's HOT (in + * more general terms a call to table_tuple_update() took + * place and set 'update_indexes' to true). Receiving this + * hint makes us consider if we should pass down the + * 'indexUnchanged' hint in turn. That's something that we + * figure out for each index_insert() call iff 'update' is + * true. (When 'update' is false we already know not to pass + * the hint to any index.) + * + * Unique and exclusion constraints are enforced at the same + * time. This returns a list of index OIDs for any unique or + * exclusion constraints that are deferred and that had + * potential (unconfirmed) conflicts. (if noDupErr == true, + * the same is done for non-deferred constraints, but report + * if conflict was speculative or deferred conflict to caller) + * + * If 'arbiterIndexes' is nonempty, noDupErr applies only to + * those indexes. NIL means noDupErr applies to all indexes. + * ---------------------------------------------------------------- + */ +List * +ExecInsertIndexTuples(ResultRelInfo *resultRelInfo, + TupleTableSlot *slot, + EState *estate, + bool update, + bool noDupErr, + bool *specConflict, + List *arbiterIndexes) +{ + ItemPointer tupleid = &slot->tts_tid; + List *result = NIL; + int i; + int numIndices; + RelationPtr relationDescs; + Relation heapRelation; + IndexInfo **indexInfoArray; + ExprContext *econtext; + Datum values[INDEX_MAX_KEYS]; + bool isnull[INDEX_MAX_KEYS]; + + Assert(ItemPointerIsValid(tupleid)); + + /* + * Get information from the result relation info structure. + */ + numIndices = resultRelInfo->ri_NumIndices; + relationDescs = resultRelInfo->ri_IndexRelationDescs; + indexInfoArray = resultRelInfo->ri_IndexRelationInfo; + heapRelation = resultRelInfo->ri_RelationDesc; + + /* Sanity check: slot must belong to the same rel as the resultRelInfo. */ + Assert(slot->tts_tableOid == RelationGetRelid(heapRelation)); + + /* + * We will use the EState's per-tuple context for evaluating predicates + * and index expressions (creating it if it's not already there). + */ + econtext = GetPerTupleExprContext(estate); + + /* Arrange for econtext's scan tuple to be the tuple under test */ + econtext->ecxt_scantuple = slot; + + /* + * for each index, form and insert the index tuple + */ + for (i = 0; i < numIndices; i++) + { + Relation indexRelation = relationDescs[i]; + IndexInfo *indexInfo; + bool applyNoDupErr; + IndexUniqueCheck checkUnique; + bool indexUnchanged; + bool satisfiesConstraint; + + if (indexRelation == NULL) + continue; + + indexInfo = indexInfoArray[i]; + + /* If the index is marked as read-only, ignore it */ + if (!indexInfo->ii_ReadyForInserts) + continue; + + /* Check for partial index */ + if (indexInfo->ii_Predicate != NIL) + { + ExprState *predicate; + + /* + * If predicate state not set up yet, create it (in the estate's + * per-query context) + */ + predicate = indexInfo->ii_PredicateState; + if (predicate == NULL) + { + predicate = ExecPrepareQual(indexInfo->ii_Predicate, estate); + indexInfo->ii_PredicateState = predicate; + } + + /* Skip this index-update if the predicate isn't satisfied */ + if (!ExecQual(predicate, econtext)) + continue; + } + + /* + * FormIndexDatum fills in its values and isnull parameters with the + * appropriate values for the column(s) of the index. + */ + FormIndexDatum(indexInfo, + slot, + estate, + values, + isnull); + + /* Check whether to apply noDupErr to this index */ + applyNoDupErr = noDupErr && + (arbiterIndexes == NIL || + list_member_oid(arbiterIndexes, + indexRelation->rd_index->indexrelid)); + + /* + * The index AM does the actual insertion, plus uniqueness checking. + * + * For an immediate-mode unique index, we just tell the index AM to + * throw error if not unique. + * + * For a deferrable unique index, we tell the index AM to just detect + * possible non-uniqueness, and we add the index OID to the result + * list if further checking is needed. + * + * For a speculative insertion (used by INSERT ... ON CONFLICT), do + * the same as for a deferrable unique index. + */ + if (!indexRelation->rd_index->indisunique) + checkUnique = UNIQUE_CHECK_NO; + else if (applyNoDupErr) + checkUnique = UNIQUE_CHECK_PARTIAL; + else if (indexRelation->rd_index->indimmediate) + checkUnique = UNIQUE_CHECK_YES; + else + checkUnique = UNIQUE_CHECK_PARTIAL; + + /* + * There's definitely going to be an index_insert() call for this + * index. If we're being called as part of an UPDATE statement, + * consider if the 'indexUnchanged' = true hint should be passed. + */ + indexUnchanged = update && index_unchanged_by_update(resultRelInfo, + estate, + indexInfo, + indexRelation); + + satisfiesConstraint = + index_insert(indexRelation, /* index relation */ + values, /* array of index Datums */ + isnull, /* null flags */ + tupleid, /* tid of heap tuple */ + heapRelation, /* heap relation */ + checkUnique, /* type of uniqueness check to do */ + indexUnchanged, /* UPDATE without logical change? */ + indexInfo); /* index AM may need this */ + + /* + * If the index has an associated exclusion constraint, check that. + * This is simpler than the process for uniqueness checks since we + * always insert first and then check. If the constraint is deferred, + * we check now anyway, but don't throw error on violation or wait for + * a conclusive outcome from a concurrent insertion; instead we'll + * queue a recheck event. Similarly, noDupErr callers (speculative + * inserters) will recheck later, and wait for a conclusive outcome + * then. + * + * An index for an exclusion constraint can't also be UNIQUE (not an + * essential property, we just don't allow it in the grammar), so no + * need to preserve the prior state of satisfiesConstraint. + */ + if (indexInfo->ii_ExclusionOps != NULL) + { + bool violationOK; + CEOUC_WAIT_MODE waitMode; + + if (applyNoDupErr) + { + violationOK = true; + waitMode = CEOUC_LIVELOCK_PREVENTING_WAIT; + } + else if (!indexRelation->rd_index->indimmediate) + { + violationOK = true; + waitMode = CEOUC_NOWAIT; + } + else + { + violationOK = false; + waitMode = CEOUC_WAIT; + } + + satisfiesConstraint = + check_exclusion_or_unique_constraint(heapRelation, + indexRelation, indexInfo, + tupleid, values, isnull, + estate, false, + waitMode, violationOK, NULL); + } + + if ((checkUnique == UNIQUE_CHECK_PARTIAL || + indexInfo->ii_ExclusionOps != NULL) && + !satisfiesConstraint) + { + /* + * The tuple potentially violates the uniqueness or exclusion + * constraint, so make a note of the index so that we can re-check + * it later. Speculative inserters are told if there was a + * speculative conflict, since that always requires a restart. + */ + result = lappend_oid(result, RelationGetRelid(indexRelation)); + if (indexRelation->rd_index->indimmediate && specConflict) + *specConflict = true; + } + } + + return result; +} + +/* ---------------------------------------------------------------- + * ExecCheckIndexConstraints + * + * This routine checks if a tuple violates any unique or + * exclusion constraints. Returns true if there is no conflict. + * Otherwise returns false, and the TID of the conflicting + * tuple is returned in *conflictTid. + * + * If 'arbiterIndexes' is given, only those indexes are checked. + * NIL means all indexes. + * + * Note that this doesn't lock the values in any way, so it's + * possible that a conflicting tuple is inserted immediately + * after this returns. But this can be used for a pre-check + * before insertion. + * ---------------------------------------------------------------- + */ +bool +ExecCheckIndexConstraints(ResultRelInfo *resultRelInfo, TupleTableSlot *slot, + EState *estate, ItemPointer conflictTid, + List *arbiterIndexes) +{ + int i; + int numIndices; + RelationPtr relationDescs; + Relation heapRelation; + IndexInfo **indexInfoArray; + ExprContext *econtext; + Datum values[INDEX_MAX_KEYS]; + bool isnull[INDEX_MAX_KEYS]; + ItemPointerData invalidItemPtr; + bool checkedIndex = false; + + ItemPointerSetInvalid(conflictTid); + ItemPointerSetInvalid(&invalidItemPtr); + + /* + * Get information from the result relation info structure. + */ + numIndices = resultRelInfo->ri_NumIndices; + relationDescs = resultRelInfo->ri_IndexRelationDescs; + indexInfoArray = resultRelInfo->ri_IndexRelationInfo; + heapRelation = resultRelInfo->ri_RelationDesc; + + /* + * We will use the EState's per-tuple context for evaluating predicates + * and index expressions (creating it if it's not already there). + */ + econtext = GetPerTupleExprContext(estate); + + /* Arrange for econtext's scan tuple to be the tuple under test */ + econtext->ecxt_scantuple = slot; + + /* + * For each index, form index tuple and check if it satisfies the + * constraint. + */ + for (i = 0; i < numIndices; i++) + { + Relation indexRelation = relationDescs[i]; + IndexInfo *indexInfo; + bool satisfiesConstraint; + + if (indexRelation == NULL) + continue; + + indexInfo = indexInfoArray[i]; + + if (!indexInfo->ii_Unique && !indexInfo->ii_ExclusionOps) + continue; + + /* If the index is marked as read-only, ignore it */ + if (!indexInfo->ii_ReadyForInserts) + continue; + + /* When specific arbiter indexes requested, only examine them */ + if (arbiterIndexes != NIL && + !list_member_oid(arbiterIndexes, + indexRelation->rd_index->indexrelid)) + continue; + + if (!indexRelation->rd_index->indimmediate) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("ON CONFLICT does not support deferrable unique constraints/exclusion constraints as arbiters"), + errtableconstraint(heapRelation, + RelationGetRelationName(indexRelation)))); + + checkedIndex = true; + + /* Check for partial index */ + if (indexInfo->ii_Predicate != NIL) + { + ExprState *predicate; + + /* + * If predicate state not set up yet, create it (in the estate's + * per-query context) + */ + predicate = indexInfo->ii_PredicateState; + if (predicate == NULL) + { + predicate = ExecPrepareQual(indexInfo->ii_Predicate, estate); + indexInfo->ii_PredicateState = predicate; + } + + /* Skip this index-update if the predicate isn't satisfied */ + if (!ExecQual(predicate, econtext)) + continue; + } + + /* + * FormIndexDatum fills in its values and isnull parameters with the + * appropriate values for the column(s) of the index. + */ + FormIndexDatum(indexInfo, + slot, + estate, + values, + isnull); + + satisfiesConstraint = + check_exclusion_or_unique_constraint(heapRelation, indexRelation, + indexInfo, &invalidItemPtr, + values, isnull, estate, false, + CEOUC_WAIT, true, + conflictTid); + if (!satisfiesConstraint) + return false; + } + + if (arbiterIndexes != NIL && !checkedIndex) + elog(ERROR, "unexpected failure to find arbiter index"); + + return true; +} + +/* + * Check for violation of an exclusion or unique constraint + * + * heap: the table containing the new tuple + * index: the index supporting the constraint + * indexInfo: info about the index, including the exclusion properties + * tupleid: heap TID of the new tuple we have just inserted (invalid if we + * haven't inserted a new tuple yet) + * values, isnull: the *index* column values computed for the new tuple + * estate: an EState we can do evaluation in + * newIndex: if true, we are trying to build a new index (this affects + * only the wording of error messages) + * waitMode: whether to wait for concurrent inserters/deleters + * violationOK: if true, don't throw error for violation + * conflictTid: if not-NULL, the TID of the conflicting tuple is returned here + * + * Returns true if OK, false if actual or potential violation + * + * 'waitMode' determines what happens if a conflict is detected with a tuple + * that was inserted or deleted by a transaction that's still running. + * CEOUC_WAIT means that we wait for the transaction to commit, before + * throwing an error or returning. CEOUC_NOWAIT means that we report the + * violation immediately; so the violation is only potential, and the caller + * must recheck sometime later. This behavior is convenient for deferred + * exclusion checks; we need not bother queuing a deferred event if there is + * definitely no conflict at insertion time. + * + * CEOUC_LIVELOCK_PREVENTING_WAIT is like CEOUC_NOWAIT, but we will sometimes + * wait anyway, to prevent livelocking if two transactions try inserting at + * the same time. This is used with speculative insertions, for INSERT ON + * CONFLICT statements. (See notes in file header) + * + * If violationOK is true, we just report the potential or actual violation to + * the caller by returning 'false'. Otherwise we throw a descriptive error + * message here. When violationOK is false, a false result is impossible. + * + * Note: The indexam is normally responsible for checking unique constraints, + * so this normally only needs to be used for exclusion constraints. But this + * function is also called when doing a "pre-check" for conflicts on a unique + * constraint, when doing speculative insertion. Caller may use the returned + * conflict TID to take further steps. + */ +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) +{ + Oid *constr_procs; + uint16 *constr_strats; + Oid *index_collations = index->rd_indcollation; + int indnkeyatts = IndexRelationGetNumberOfKeyAttributes(index); + IndexScanDesc index_scan; + ScanKeyData scankeys[INDEX_MAX_KEYS]; + SnapshotData DirtySnapshot; + int i; + bool conflict; + bool found_self; + ExprContext *econtext; + TupleTableSlot *existing_slot; + TupleTableSlot *save_scantuple; + + if (indexInfo->ii_ExclusionOps) + { + constr_procs = indexInfo->ii_ExclusionProcs; + constr_strats = indexInfo->ii_ExclusionStrats; + } + else + { + constr_procs = indexInfo->ii_UniqueProcs; + constr_strats = indexInfo->ii_UniqueStrats; + } + + /* + * If any of the input values are NULL, and the index uses the default + * nulls-are-distinct mode, the constraint check is assumed to pass (i.e., + * we assume the operators are strict). Otherwise, we interpret the + * constraint as specifying IS NULL for each column whose input value is + * NULL. + */ + if (!indexInfo->ii_NullsNotDistinct) + { + for (i = 0; i < indnkeyatts; i++) + { + if (isnull[i]) + return true; + } + } + + /* + * Search the tuples that are in the index for any violations, including + * tuples that aren't visible yet. + */ + InitDirtySnapshot(DirtySnapshot); + + for (i = 0; i < indnkeyatts; i++) + { + ScanKeyEntryInitialize(&scankeys[i], + isnull[i] ? SK_ISNULL | SK_SEARCHNULL : 0, + i + 1, + constr_strats[i], + InvalidOid, + index_collations[i], + constr_procs[i], + values[i]); + } + + /* + * Need a TupleTableSlot to put existing tuples in. + * + * To use FormIndexDatum, we have to make the econtext's scantuple point + * to this slot. Be sure to save and restore caller's value for + * scantuple. + */ + existing_slot = table_slot_create(heap, NULL); + + econtext = GetPerTupleExprContext(estate); + save_scantuple = econtext->ecxt_scantuple; + econtext->ecxt_scantuple = existing_slot; + + /* + * May have to restart scan from this point if a potential conflict is + * found. + */ +retry: + conflict = false; + found_self = false; + index_scan = index_beginscan(heap, index, &DirtySnapshot, indnkeyatts, 0); + index_rescan(index_scan, scankeys, indnkeyatts, NULL, 0); + + while (index_getnext_slot(index_scan, ForwardScanDirection, existing_slot)) + { + TransactionId xwait; + XLTW_Oper reason_wait; + Datum existing_values[INDEX_MAX_KEYS]; + bool existing_isnull[INDEX_MAX_KEYS]; + char *error_new; + char *error_existing; + + /* + * Ignore the entry for the tuple we're trying to check. + */ + if (ItemPointerIsValid(tupleid) && + ItemPointerEquals(tupleid, &existing_slot->tts_tid)) + { + if (found_self) /* should not happen */ + elog(ERROR, "found self tuple multiple times in index \"%s\"", + RelationGetRelationName(index)); + found_self = true; + continue; + } + + /* + * Extract the index column values and isnull flags from the existing + * tuple. + */ + FormIndexDatum(indexInfo, existing_slot, estate, + existing_values, existing_isnull); + + /* If lossy indexscan, must recheck the condition */ + if (index_scan->xs_recheck) + { + if (!index_recheck_constraint(index, + constr_procs, + existing_values, + existing_isnull, + values)) + continue; /* tuple doesn't actually match, so no + * conflict */ + } + + /* + * At this point we have either a conflict or a potential conflict. + * + * If an in-progress transaction is affecting the visibility of this + * tuple, we need to wait for it to complete and then recheck (unless + * the caller requested not to). For simplicity we do rechecking by + * just restarting the whole scan --- this case probably doesn't + * happen often enough to be worth trying harder, and anyway we don't + * want to hold any index internal locks while waiting. + */ + xwait = TransactionIdIsValid(DirtySnapshot.xmin) ? + DirtySnapshot.xmin : DirtySnapshot.xmax; + + if (TransactionIdIsValid(xwait) && + (waitMode == CEOUC_WAIT || + (waitMode == CEOUC_LIVELOCK_PREVENTING_WAIT && + DirtySnapshot.speculativeToken && + TransactionIdPrecedes(GetCurrentTransactionId(), xwait)))) + { + reason_wait = indexInfo->ii_ExclusionOps ? + XLTW_RecheckExclusionConstr : XLTW_InsertIndex; + index_endscan(index_scan); + if (DirtySnapshot.speculativeToken) + SpeculativeInsertionWait(DirtySnapshot.xmin, + DirtySnapshot.speculativeToken); + else + XactLockTableWait(xwait, heap, + &existing_slot->tts_tid, reason_wait); + goto retry; + } + + /* + * We have a definite conflict (or a potential one, but the caller + * didn't want to wait). Return it to caller, or report it. + */ + if (violationOK) + { + conflict = true; + if (conflictTid) + *conflictTid = existing_slot->tts_tid; + break; + } + + error_new = BuildIndexValueDescription(index, values, isnull); + error_existing = BuildIndexValueDescription(index, existing_values, + existing_isnull); + if (newIndex) + ereport(ERROR, + (errcode(ERRCODE_EXCLUSION_VIOLATION), + errmsg("could not create exclusion constraint \"%s\"", + RelationGetRelationName(index)), + error_new && error_existing ? + errdetail("Key %s conflicts with key %s.", + error_new, error_existing) : + errdetail("Key conflicts exist."), + errtableconstraint(heap, + RelationGetRelationName(index)))); + else + ereport(ERROR, + (errcode(ERRCODE_EXCLUSION_VIOLATION), + errmsg("conflicting key value violates exclusion constraint \"%s\"", + RelationGetRelationName(index)), + error_new && error_existing ? + errdetail("Key %s conflicts with existing key %s.", + error_new, error_existing) : + errdetail("Key conflicts with existing key."), + errtableconstraint(heap, + RelationGetRelationName(index)))); + } + + index_endscan(index_scan); + + /* + * Ordinarily, at this point the search should have found the originally + * inserted tuple (if any), unless we exited the loop early because of + * conflict. However, it is possible to define exclusion constraints for + * which that wouldn't be true --- for instance, if the operator is <>. So + * we no longer complain if found_self is still false. + */ + + econtext->ecxt_scantuple = save_scantuple; + + ExecDropSingleTupleTableSlot(existing_slot); + + return !conflict; +} + +/* + * Check for violation of an exclusion constraint + * + * This is a dumbed down version of check_exclusion_or_unique_constraint + * for external callers. They don't need all the special modes. + */ +void +check_exclusion_constraint(Relation heap, Relation index, + IndexInfo *indexInfo, + ItemPointer tupleid, + Datum *values, bool *isnull, + EState *estate, bool newIndex) +{ + (void) check_exclusion_or_unique_constraint(heap, index, indexInfo, tupleid, + values, isnull, + estate, newIndex, + CEOUC_WAIT, false, NULL); +} + +/* + * Check existing tuple's index values to see if it really matches the + * exclusion condition against the new_values. Returns true if conflict. + */ +static bool +index_recheck_constraint(Relation index, Oid *constr_procs, + Datum *existing_values, bool *existing_isnull, + Datum *new_values) +{ + int indnkeyatts = IndexRelationGetNumberOfKeyAttributes(index); + int i; + + for (i = 0; i < indnkeyatts; i++) + { + /* Assume the exclusion operators are strict */ + if (existing_isnull[i]) + return false; + + if (!DatumGetBool(OidFunctionCall2Coll(constr_procs[i], + index->rd_indcollation[i], + existing_values[i], + new_values[i]))) + return false; + } + + return true; +} + +/* + * Check if ExecInsertIndexTuples() should pass indexUnchanged hint. + * + * When the executor performs an UPDATE that requires a new round of index + * tuples, determine if we should pass 'indexUnchanged' = true hint for one + * single index. + */ +static bool +index_unchanged_by_update(ResultRelInfo *resultRelInfo, EState *estate, + IndexInfo *indexInfo, Relation indexRelation) +{ + Bitmapset *updatedCols; + Bitmapset *extraUpdatedCols; + Bitmapset *allUpdatedCols; + bool hasexpression = false; + List *idxExprs; + + /* + * Check cache first + */ + if (indexInfo->ii_CheckedUnchanged) + return indexInfo->ii_IndexUnchanged; + indexInfo->ii_CheckedUnchanged = true; + + /* + * Check for indexed attribute overlap with updated columns. + * + * Only do this for key columns. A change to a non-key column within an + * INCLUDE index should not be counted here. Non-key column values are + * opaque payload state to the index AM, a little like an extra table TID. + * + * Note that row-level BEFORE triggers won't affect our behavior, since + * they don't affect the updatedCols bitmaps generally. It doesn't seem + * worth the trouble of checking which attributes were changed directly. + */ + updatedCols = ExecGetUpdatedCols(resultRelInfo, estate); + extraUpdatedCols = ExecGetExtraUpdatedCols(resultRelInfo, estate); + for (int attr = 0; attr < indexInfo->ii_NumIndexKeyAttrs; attr++) + { + int keycol = indexInfo->ii_IndexAttrNumbers[attr]; + + if (keycol <= 0) + { + /* + * Skip expressions for now, but remember to deal with them later + * on + */ + hasexpression = true; + continue; + } + + if (bms_is_member(keycol - FirstLowInvalidHeapAttributeNumber, + updatedCols) || + bms_is_member(keycol - FirstLowInvalidHeapAttributeNumber, + extraUpdatedCols)) + { + /* Changed key column -- don't hint for this index */ + indexInfo->ii_IndexUnchanged = false; + return false; + } + } + + /* + * When we get this far and index has no expressions, return true so that + * index_insert() call will go on to pass 'indexUnchanged' = true hint. + * + * The _absence_ of an indexed key attribute that overlaps with updated + * attributes (in addition to the total absence of indexed expressions) + * shows that the index as a whole is logically unchanged by UPDATE. + */ + if (!hasexpression) + { + indexInfo->ii_IndexUnchanged = true; + return true; + } + + /* + * Need to pass only one bms to expression_tree_walker helper function. + * Avoid allocating memory in common case where there are no extra cols. + */ + if (!extraUpdatedCols) + allUpdatedCols = updatedCols; + else + allUpdatedCols = bms_union(updatedCols, extraUpdatedCols); + + /* + * We have to work slightly harder in the event of indexed expressions, + * but the principle is the same as before: try to find columns (Vars, + * actually) that overlap with known-updated columns. + * + * If we find any matching Vars, don't pass hint for index. Otherwise + * pass hint. + */ + idxExprs = RelationGetIndexExpressions(indexRelation); + hasexpression = index_expression_changed_walker((Node *) idxExprs, + allUpdatedCols); + list_free(idxExprs); + if (extraUpdatedCols) + bms_free(allUpdatedCols); + + if (hasexpression) + { + indexInfo->ii_IndexUnchanged = false; + return false; + } + + /* + * Deliberately don't consider index predicates. We should even give the + * hint when result rel's "updated tuple" has no corresponding index + * tuple, which is possible with a partial index (provided the usual + * conditions are met). + */ + indexInfo->ii_IndexUnchanged = true; + return true; +} + +/* + * Indexed expression helper for index_unchanged_by_update(). + * + * Returns true when Var that appears within allUpdatedCols located. + */ +static bool +index_expression_changed_walker(Node *node, Bitmapset *allUpdatedCols) +{ + if (node == NULL) + return false; + + if (IsA(node, Var)) + { + Var *var = (Var *) node; + + if (bms_is_member(var->varattno - FirstLowInvalidHeapAttributeNumber, + allUpdatedCols)) + { + /* Var was updated -- indicates that we should not hint */ + return true; + } + + /* Still haven't found a reason to not pass the hint */ + return false; + } + + return expression_tree_walker(node, index_expression_changed_walker, + (void *) allUpdatedCols); +} |