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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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13
src/backend/rewrite/rewriteDefine.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/rewrite/rewriteDefine.c,v 1.141 2010/02/14 18:42:15 rhaas Exp $
* $PostgreSQL: pgsql/src/backend/rewrite/rewriteDefine.c,v 1.142 2010/07/28 05:22:24 sriggs Exp $
*
*-------------------------------------------------------------------------
*/
@ -236,11 +236,14 @@ DefineQueryRewrite(char *rulename,
/*
* If we are installing an ON SELECT rule, we had better grab
* AccessExclusiveLock to ensure no SELECTs are currently running on the
* event relation. For other types of rules, it might be sufficient to
* grab ShareLock to lock out insert/update/delete actions. But for now,
* let's just grab AccessExclusiveLock all the time.
* event relation. For other types of rules, it is sufficient to
* grab ShareRowExclusiveLock to lock out insert/update/delete actions
* and to ensure that we lock out current CREATE RULE statements.
*/
event_relation = heap_open(event_relid, AccessExclusiveLock);
if (event_type == CMD_SELECT)
event_relation = heap_open(event_relid, AccessExclusiveLock);
else
event_relation = heap_open(event_relid, ShareRowExclusiveLock);
/*
* Verify relation is of a type that rules can sensibly be applied to.