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Reduce lock levels of CREATE TRIGGER and some ALTER TABLE, CREATE RULE actions.

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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.
This commit is contained in:
Simon Riggs
2010-07-28 05:22:24 +00:00
parent 133924e13e
commit 2dbbda02e7
10 changed files with 426 additions and 232 deletions
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20
src/backend/commands/trigger.c
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@ -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,