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PortalRun must guard against the possibility that the portal it's

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running contains VACUUM or a similar command that will internally start
and commit transactions.  In such a case, the original caller values of
CurrentMemoryContext and CurrentResourceOwner will point to objects that
will be destroyed by the internal commit.  We must restore these pointers
to point to the newly-manufactured transaction context and resource owner,
rather than possibly pointing to deleted memory.
Also tweak xact.c so that AbortTransaction and AbortSubTransaction
forcibly restore a sane value for CurrentResourceOwner, much as they
have always done for CurrentMemoryContext.  I'm not certain this is
necessary but I'm feeling paranoid today.
Responds to Sean Chittenden's bug report of 4-Oct.
This commit is contained in:
Tom Lane
2004-10-04 21:52:15 +00:00
parent ee7de3d662
commit 4c77cbb272
2 changed files with 68 additions and 10 deletions
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42
src/backend/tcop/pquery.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.87 2004/09/13 20:07:05 tgl Exp $
* $PostgreSQL: pgsql/src/backend/tcop/pquery.c,v 1.88 2004/10/04 21:52:15 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -491,12 +491,14 @@ PortalRun(Portal portal, long count,
char *completionTag)
{
bool result;
ResourceOwner saveTopTransactionResourceOwner;
MemoryContext saveTopTransactionContext;
Portal saveActivePortal;
Snapshot saveActiveSnapshot;
ResourceOwner saveResourceOwner;
MemoryContext savePortalContext;
MemoryContext saveQueryContext;
MemoryContext oldContext;
MemoryContext saveMemoryContext;
AssertArg(PortalIsValid(portal));
@ -523,12 +525,26 @@ PortalRun(Portal portal, long count,
/*
* Set up global portal context pointers.
*
* We have to play a special game here to support utility commands like
* VACUUM and CLUSTER, which internally start and commit transactions.
* When we are called to execute such a command, CurrentResourceOwner
* will be pointing to the TopTransactionResourceOwner --- which will
* be destroyed and replaced in the course of the internal commit and
* restart. So we need to be prepared to restore it as pointing to
* the exit-time TopTransactionResourceOwner. (Ain't that ugly? This
* idea of internally starting whole new transactions is not good.)
* CurrentMemoryContext has a similar problem, but the other pointers
* we save here will be NULL or pointing to longer-lived objects.
*/
saveTopTransactionResourceOwner = TopTransactionResourceOwner;
saveTopTransactionContext = TopTransactionContext;
saveActivePortal = ActivePortal;
saveActiveSnapshot = ActiveSnapshot;
saveResourceOwner = CurrentResourceOwner;
savePortalContext = PortalContext;
saveQueryContext = QueryContext;
saveMemoryContext = CurrentMemoryContext;
PG_TRY();
{
ActivePortal = portal;
@ -537,7 +553,7 @@ PortalRun(Portal portal, long count,
PortalContext = PortalGetHeapMemory(portal);
QueryContext = portal->queryContext;
oldContext = MemoryContextSwitchTo(PortalContext);
MemoryContextSwitchTo(PortalContext);
switch (portal->strategy)
{
@ -620,9 +636,16 @@ PortalRun(Portal portal, long count,
portal->status = PORTAL_FAILED;
/* Restore global vars and propagate error */
if (saveMemoryContext == saveTopTransactionContext)
MemoryContextSwitchTo(TopTransactionContext);
else
MemoryContextSwitchTo(saveMemoryContext);
ActivePortal = saveActivePortal;
ActiveSnapshot = saveActiveSnapshot;
CurrentResourceOwner = saveResourceOwner;
if (saveResourceOwner == saveTopTransactionResourceOwner)
CurrentResourceOwner = TopTransactionResourceOwner;
else
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
QueryContext = saveQueryContext;
@ -630,11 +653,16 @@ PortalRun(Portal portal, long count,
}
PG_END_TRY();
MemoryContextSwitchTo(oldContext);
if (saveMemoryContext == saveTopTransactionContext)
MemoryContextSwitchTo(TopTransactionContext);
else
MemoryContextSwitchTo(saveMemoryContext);
ActivePortal = saveActivePortal;
ActiveSnapshot = saveActiveSnapshot;
CurrentResourceOwner = saveResourceOwner;
if (saveResourceOwner == saveTopTransactionResourceOwner)
CurrentResourceOwner = TopTransactionResourceOwner;
else
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
QueryContext = saveQueryContext;