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Prevent RevalidateCachedPlan from making any permanent change in 

ActiveSnapshot.  Having it affect ActiveSnapshot only in the unusual
case of needing to replan seems a bad idea, and there's also the problem
that the created snap might be in a relatively short-lived context, as
noted by Jan Wieck.  Also, there's no need to force a new snap at all
unless we are called with no snap currently set, which is an unusual
case in itself.
This commit is contained in:
Tom Lane 2007-05-14 18:13:21 +00:00
parent 689dea424d
commit fd53a67dcd
1 changed files with 47 additions and 7 deletions
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54
src/backend/utils/cache/plancache.c vendored
View File

@ -33,7 +33,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.8 2007/04/16 18:21:07 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.9 2007/05/14 18:13:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -69,6 +69,7 @@ static List *cached_plans_list = NIL;
static void StoreCachedPlan(CachedPlanSource *plansource, List *stmt_list,
MemoryContext plan_context);
static List *do_planning(List *querytrees, int cursorOptions);
static void AcquireExecutorLocks(List *stmt_list, bool acquire);
static void AcquirePlannerLocks(List *stmt_list, bool acquire);
static void LockRelid(Oid relid, LOCKMODE lockmode, void *arg);
@ -462,12 +463,8 @@ RevalidateCachedPlan(CachedPlanSource *plansource, bool useResOwner)
if (plansource->fully_planned)
{
/*
* Generate plans for queries. Assume snapshot is not set yet
* (XXX this may be wasteful, won't all callers have done that?)
*/
slist = pg_plan_queries(slist, plansource->cursor_options, NULL,
true);
/* Generate plans for queries */
slist = do_planning(slist, plansource->cursor_options);
}
/*
@ -522,6 +519,49 @@ RevalidateCachedPlan(CachedPlanSource *plansource, bool useResOwner)
return plan;
}
/*
* Invoke the planner on some rewritten queries. This is broken out of
* RevalidateCachedPlan just to avoid plastering "volatile" all over that
* function's variables.
*/
static List *
do_planning(List *querytrees, int cursorOptions)
{
List *stmt_list;
/*
* If a snapshot is already set (the normal case), we can just use that
* for planning. But if it isn't, we have to tell pg_plan_queries to make
* a snap if it needs one. In that case we should arrange to reset
* ActiveSnapshot afterward, to ensure that RevalidateCachedPlan has no
* caller-visible effects on the snapshot. Having to replan is an unusual
* case, and it seems a really bad idea for RevalidateCachedPlan to affect
* the snapshot only in unusual cases. (Besides, the snap might have
* been created in a short-lived context.)
*/
if (ActiveSnapshot != NULL)
stmt_list = pg_plan_queries(querytrees, cursorOptions, NULL, false);
else
{
PG_TRY();
{
stmt_list = pg_plan_queries(querytrees, cursorOptions, NULL, true);
}
PG_CATCH();
{
/* Restore global vars and propagate error */
ActiveSnapshot = NULL;
PG_RE_THROW();
}
PG_END_TRY();
ActiveSnapshot = NULL;
}
return stmt_list;
}
/*
* ReleaseCachedPlan: release active use of a cached plan.
*