From 4c77cbb272948e96ce3ed02d444a944eb45d45e3 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 4 Oct 2004 21:52:15 +0000
Subject: [PATCH] PortalRun must guard against the possibility that the portal
it's 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.
---
src/backend/access/transam/xact.c | 36 +++++++++++++++++++++++---
src/backend/tcop/pquery.c | 42 +++++++++++++++++++++++++------
2 files changed, 68 insertions(+), 10 deletions(-)
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 17db7dd78d5..321a86f30c2 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.190 2004/09/16 20:17:16 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.191 2004/10/04 21:52:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -205,6 +205,7 @@ static void AssignSubTransactionId(TransactionState s);
static void AbortTransaction(void);
static void AtAbort_Memory(void);
static void AtCleanup_Memory(void);
+static void AtAbort_ResourceOwner(void);
static void AtCommit_LocalCache(void);
static void AtCommit_Memory(void);
static void AtStart_Cache(void);
@@ -229,6 +230,7 @@ static void PopTransaction(void);
static void AtSubAbort_Memory(void);
static void AtSubCleanup_Memory(void);
+static void AtSubAbort_ResourceOwner(void);
static void AtSubCommit_Memory(void);
static void AtSubStart_Memory(void);
static void AtSubStart_ResourceOwner(void);
@@ -1103,7 +1105,6 @@ AtAbort_Memory(void)
MemoryContextSwitchTo(TopMemoryContext);
}
-
/*
* AtSubAbort_Memory
*/
@@ -1115,6 +1116,33 @@ AtSubAbort_Memory(void)
MemoryContextSwitchTo(TopTransactionContext);
}
+
+/*
+ * AtAbort_ResourceOwner
+ */
+static void
+AtAbort_ResourceOwner(void)
+{
+ /*
+ * Make sure we have a valid ResourceOwner, if possible (else it
+ * will be NULL, which is OK)
+ */
+ CurrentResourceOwner = TopTransactionResourceOwner;
+}
+
+/*
+ * AtSubAbort_ResourceOwner
+ */
+static void
+AtSubAbort_ResourceOwner(void)
+{
+ TransactionState s = CurrentTransactionState;
+
+ /* Make sure we have a valid ResourceOwner */
+ CurrentResourceOwner = s->curTransactionOwner;
+}
+
+
/*
* AtSubAbort_childXids
*/
@@ -1598,8 +1626,9 @@ AbortTransaction(void)
*/
s->state = TRANS_ABORT;
- /* Make sure we are in a valid memory context */
+ /* Make sure we have a valid memory context and resource owner */
AtAbort_Memory();
+ AtAbort_ResourceOwner();
/*
* Reset user id which might have been changed transiently. We cannot
@@ -3338,6 +3367,7 @@ AbortSubTransaction(void)
* do abort processing
*/
AtSubAbort_Memory();
+ AtSubAbort_ResourceOwner();
/*
* We can skip all this stuff if the subxact failed before creating
diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index 5a1c8b4867b..2c4c2f3c7e5 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -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;
--
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