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Fix PREPARE TRANSACTION to reject the case where the transaction has dropped a

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temporary table; we can't support that because there's no way to clean up the
source backend's internal state if the eventual COMMIT PREPARED is done by
another backend.  This was checked correctly in 8.1 but I broke it in 8.2 :-(.
Patch by Heikki Linnakangas, original trouble report by John Smith.
This commit is contained in:
Tom Lane
2008-03-04 19:54:06 +00:00
parent 9b8a93baa4
commit 7d6e6e2e97
6 changed files with 49 additions and 56 deletions
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30
src/backend/access/transam/xact.c
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@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.257 2008/01/15 18:56:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.258 2008/03/04 19:54:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -62,6 +62,13 @@ bool XactSyncCommit = true;
int CommitDelay = 0; /* precommit delay in microseconds */
int CommitSiblings = 5; /* # concurrent xacts needed to sleep */
/*
* MyXactAccessedTempRel is set when a temporary relation is accessed.
* We don't allow PREPARE TRANSACTION in that case. (This is global
* so that it can be set from heapam.c.)
*/
bool MyXactAccessedTempRel = false;
/*
* transaction states - transaction state from server perspective
@ -1445,6 +1452,7 @@ StartTransaction(void)
XactIsoLevel = DefaultXactIsoLevel;
XactReadOnly = DefaultXactReadOnly;
forceSyncCommit = false;
MyXactAccessedTempRel = false;
/*
* reinitialize within-transaction counters
@ -1770,6 +1778,26 @@ PrepareTransaction(void)
/* NOTIFY and flatfiles will be handled below */
/*
* Don't allow PREPARE TRANSACTION if we've accessed a temporary table
* in this transaction. Having the prepared xact hold locks on another
* backend's temp table seems a bad idea --- for instance it would prevent
* the backend from exiting. There are other problems too, such as how
* to clean up the source backend's local buffers and ON COMMIT state
* if the prepared xact includes a DROP of a temp table.
*
* We must check this after executing any ON COMMIT actions, because
* they might still access a temp relation.
*
* XXX In principle this could be relaxed to allow some useful special
* cases, such as a temp table created and dropped all within the
* transaction. That seems to require much more bookkeeping though.
*/
if (MyXactAccessedTempRel)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
/* Prevent cancel/die interrupt while cleaning up */
HOLD_INTERRUPTS();