diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 1e737a0..ece6ed5 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -2862,13 +2862,8 @@ AlterTableGetLockLevel(List *cmds) break; /* - * These subcommands affect write operations only. XXX - * Theoretically, these could be ShareRowExclusiveLock. + * These subcommands affect write operations only. */ - case AT_ColumnDefault: - case AT_ProcessedConstraint: /* becomes AT_AddConstraint */ - case AT_AddConstraintRecurse: /* becomes AT_AddConstraint */ - case AT_ReAddConstraint: /* becomes AT_AddConstraint */ case AT_EnableTrig: case AT_EnableAlwaysTrig: case AT_EnableReplicaTrig: @@ -2877,6 +2872,17 @@ AlterTableGetLockLevel(List *cmds) case AT_DisableTrig: case AT_DisableTrigAll: case AT_DisableTrigUser: + cmd_lockmode = ShareRowExclusiveLock; + break; + + /* + * These subcommands affect write operations only. XXX + * Theoretically, these could be ShareRowExclusiveLock. + */ + case AT_ColumnDefault: + case AT_ProcessedConstraint: /* becomes AT_AddConstraint */ + case AT_AddConstraintRecurse: /* becomes AT_AddConstraint */ + case AT_ReAddConstraint: /* becomes AT_AddConstraint */ case AT_AlterConstraint: case AT_AddIndex: /* from ADD CONSTRAINT */ case AT_AddIndexConstraint: @@ -2913,11 +2919,9 @@ AlterTableGetLockLevel(List *cmds) /* * We add triggers to both tables when we add a * Foreign Key, so the lock level must be at least - * as strong as CREATE TRIGGER. XXX Might be set - * down to ShareRowExclusiveLock though trigger - * info is accessed by pg_get_triggerdef + * as strong as CREATE TRIGGER. */ - cmd_lockmode = AccessExclusiveLock; + cmd_lockmode = ShareRowExclusiveLock; break; default: @@ -6034,16 +6038,13 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel, ListCell *old_pfeqop_item = list_head(fkconstraint->old_conpfeqop); /* - * Grab an exclusive lock on the pk table, so that someone doesn't delete - * rows out from under us. (Although a lesser lock would do for that - * purpose, we'll need exclusive lock anyway to add triggers to the pk - * table; trying to start with a lesser lock will just create a risk of - * deadlock.) + * Grab an share lock on the pk table, so that someone doesn't delete + * rows out from under us. */ if (OidIsValid(fkconstraint->old_pktable_oid)) - pkrel = heap_open(fkconstraint->old_pktable_oid, AccessExclusiveLock); + pkrel = heap_open(fkconstraint->old_pktable_oid, ShareRowExclusiveLock); else - pkrel = heap_openrv(fkconstraint->pktable, AccessExclusiveLock); + pkrel = heap_openrv(fkconstraint->pktable, ShareRowExclusiveLock); /* * Validity checks (permission checks wait till we have the column diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c index ebccfea..b2d5a52 100644 --- a/src/backend/commands/trigger.c +++ b/src/backend/commands/trigger.c @@ -158,9 +158,9 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString, referenced; if (OidIsValid(relOid)) - rel = heap_open(relOid, AccessExclusiveLock); + rel = heap_open(relOid, ShareRowExclusiveLock); else - rel = heap_openrv(stmt->relation, AccessExclusiveLock); + rel = heap_openrv(stmt->relation, ShareRowExclusiveLock); /* * Triggers must be on tables or views, and there are additional @@ -526,8 +526,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString, * can skip this for internally generated triggers, since the name * modification above should be sufficient. * - * NOTE that this is cool only because we have AccessExclusiveLock on the - * relation, so the trigger set won't be changing underneath us. + * NOTE that this is cool only because of the unique contraint. */ if (!isInternal) { @@ -1258,7 +1257,7 @@ renametrig(RenameStmt *stmt) * Look up name, check permissions, and acquire lock (which we will NOT * release until end of transaction). */ - relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock, + relid = RangeVarGetRelidExtended(stmt->relation, ShareRowExclusiveLock, false, false, RangeVarCallbackForRenameTrigger, NULL); @@ -1272,8 +1271,7 @@ renametrig(RenameStmt *stmt) * on tgrelid/tgname would complain anyway) and to ensure a trigger does * exist with oldname. * - * NOTE that this is cool only because we have AccessExclusiveLock on the - * relation, so the trigger set won't be changing underneath us. + * NOTE that this is cool only because there is a unique constraint. */ tgrel = heap_open(TriggerRelationId, RowExclusiveLock); diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c index 24ade6c..4deb9c2 100644 --- a/src/backend/utils/adt/ruleutils.c +++ b/src/backend/utils/adt/ruleutils.c @@ -699,7 +699,8 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty) HeapTuple ht_trig; Form_pg_trigger trigrec; StringInfoData buf; - Relation tgrel; + Snapshot snapshot = RegisterSnapshot(GetTransactionSnapshot()); + Relation tgrel = heap_open(TriggerRelationId, AccessShareLock); ScanKeyData skey[1]; SysScanDesc tgscan; int findx = 0; @@ -710,18 +711,18 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty) /* * Fetch the pg_trigger tuple by the Oid of the trigger */ - tgrel = heap_open(TriggerRelationId, AccessShareLock); - ScanKeyInit(&skey[0], ObjectIdAttributeNumber, BTEqualStrategyNumber, F_OIDEQ, ObjectIdGetDatum(trigid)); tgscan = systable_beginscan(tgrel, TriggerOidIndexId, true, - NULL, 1, skey); + snapshot, 1, skey); ht_trig = systable_getnext(tgscan); + UnregisterSnapshot(snapshot); + if (!HeapTupleIsValid(ht_trig)) elog(ERROR, "could not find tuple for trigger %u", trigid); diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out index d233710..1f7c265 100644 --- a/src/test/regress/expected/alter_table.out +++ b/src/test/regress/expected/alter_table.out @@ -1952,9 +1952,9 @@ create trigger ttdummy execute procedure ttdummy (1, 1); select * from my_locks order by 1; - relname | max_lockmode ------------+--------------------- - alterlock | AccessExclusiveLock + relname | max_lockmode +-----------+----------------------- + alterlock | ShareRowExclusiveLock (1 row) rollback; @@ -1966,10 +1966,10 @@ select * from my_locks order by 1; alter table alterlock2 add foreign key (f1) references alterlock (f1); select * from my_locks order by 1; - relname | max_lockmode ------------------+--------------------- - alterlock | AccessExclusiveLock - alterlock2 | AccessExclusiveLock + relname | max_lockmode +-----------------+----------------------- + alterlock | ShareRowExclusiveLock + alterlock2 | ShareRowExclusiveLock alterlock2_pkey | AccessShareLock alterlock_pkey | AccessShareLock (4 rows) @@ -1979,10 +1979,10 @@ begin; alter table alterlock2 add constraint alterlock2nv foreign key (f1) references alterlock (f1) NOT VALID; select * from my_locks order by 1; - relname | max_lockmode -------------+--------------------- - alterlock | AccessExclusiveLock - alterlock2 | AccessExclusiveLock + relname | max_lockmode +------------+----------------------- + alterlock | ShareRowExclusiveLock + alterlock2 | ShareRowExclusiveLock (2 rows) commit;