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| author | Simon Riggs <simon@2ndQuadrant.com> | 2010-07-28 05:22:24 +0000 |
|---|---|---|
| committer | Simon Riggs <simon@2ndQuadrant.com> | 2010-07-28 05:22:24 +0000 |
| commit | 2dbbda02e7e688311e161a912a0ce00cde9bb6fc (patch) | |
| tree | adf4f2ca8c477550f19bd6362d0b6fa4ae19f68b /src/backend/commands/trigger.c | |
| parent | 133924e13e004db8979424bf5436e21b0a09a069 (diff) | |
| download | postgresql-2dbbda02e7e688311e161a912a0ce00cde9bb6fc.tar.gz postgresql-2dbbda02e7e688311e161a912a0ce00cde9bb6fc.zip | |
Reduce lock levels of CREATE TRIGGER and some ALTER TABLE, CREATE RULE actions.
Avoid hard-coding lockmode used for many altering DDL commands, allowing easier
future changes of lock levels. Implementation of initial analysis on DDL
sub-commands, so that many lock levels are now at ShareUpdateExclusiveLock or
ShareRowExclusiveLock, allowing certain DDL not to block reads/writes.
First of number of planned changes in this area; additional docs required
when full project complete.
Diffstat (limited to 'src/backend/commands/trigger.c')
| -rw-r--r-- | src/backend/commands/trigger.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c index aef7838eb6e..643b7b3a6f1 100644 --- a/src/backend/commands/trigger.c +++ b/src/backend/commands/trigger.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.262 2010/02/26 02:00:39 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.263 2010/07/28 05:22:24 sriggs Exp $ * *------------------------------------------------------------------------- */ @@ -141,7 +141,14 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString, ObjectAddress myself, referenced; - rel = heap_openrv(stmt->relation, AccessExclusiveLock); + /* + * ShareRowExclusiveLock is sufficient to prevent concurrent write activity + * to the relation, and thus to lock out any operations that might want to + * fire triggers on the relation. If we had ON SELECT triggers we would + * need to take an AccessExclusiveLock to add one of those, just as we do + * with ON SELECT rules. + */ + rel = heap_openrv(stmt->relation, ShareRowExclusiveLock); if (rel->rd_rel->relkind != RELKIND_RELATION) ereport(ERROR, @@ -417,7 +424,7 @@ 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 + * NOTE that this is cool only because we have ShareRowExclusiveLock on the * relation, so the trigger set won't be changing underneath us. */ if (!isInternal) @@ -1051,11 +1058,14 @@ RemoveTriggerById(Oid trigOid) elog(ERROR, "could not find tuple for trigger %u", trigOid); /* - * Open and exclusive-lock the relation the trigger belongs to. + * Open and lock the relation the trigger belongs to. As in + * CreateTrigger, this is sufficient to lock out all operations that + * could fire or add triggers; but it would need to be revisited if + * we had ON SELECT triggers. */ relid = ((Form_pg_trigger) GETSTRUCT(tup))->tgrelid; - rel = heap_open(relid, AccessExclusiveLock); + rel = heap_open(relid, ShareRowExclusiveLock); if (rel->rd_rel->relkind != RELKIND_RELATION) ereport(ERROR, |