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Tighten up application of parallel mode checks.

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Commit 924bcf4f16 failed to enforce
parallel mode checks during the commit of a parallel worker, because
we exited parallel mode prior to ending the transaction so that we
could pop the active snapshot.  Re-establish parallel mode during
parallel worker commit.  Without this, it's far too easy for unsafe
actions during the pre-commit sequence to crash the server instead of
hitting the error checks as intended.

Just to be extra paranoid, adjust a couple of the sanity checks in
xact.c to check not only IsInParallelMode() but also
IsParallelWorker().
This commit is contained in:
Robert Haas 2015-10-16 09:59:57 -04:00
parent 423ec0877f
commit 94b4f7e2a6
1 changed files with 7 additions and 5 deletions
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12
src/backend/access/transam/xact.c
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@ -497,7 +497,7 @@ AssignTransactionId(TransactionState s)
* Workers synchronize transaction state at the beginning of each parallel
* operation, so we can't account for new XIDs at this point.
*/
if (IsInParallelMode())
if (IsInParallelMode() || IsParallelWorker())
elog(ERROR, "cannot assign XIDs during a parallel operation");
/*
@ -931,7 +931,7 @@ CommandCounterIncrement(void)
* parallel operation, so we can't account for new commands after that
* point.
*/
if (IsInParallelMode())
if (IsInParallelMode() || IsParallelWorker())
elog(ERROR, "cannot start commands during a parallel operation");
currentCommandId += 1;
@ -1927,6 +1927,10 @@ CommitTransaction(void)
is_parallel_worker = (s->blockState == TBLOCK_PARALLEL_INPROGRESS);
/* Enforce parallel mode restrictions during parallel worker commit. */
if (is_parallel_worker)
EnterParallelMode();
ShowTransactionState("CommitTransaction");
/*
@ -1971,10 +1975,7 @@ CommitTransaction(void)
/* If we might have parallel workers, clean them up now. */
if (IsInParallelMode())
{
AtEOXact_Parallel(true);
s->parallelModeLevel = 0;
}
/* Shut down the deferred-trigger manager */
AfterTriggerEndXact(true);
@ -2013,6 +2014,7 @@ CommitTransaction(void)
* commit processing
*/
s->state = TRANS_COMMIT;
s->parallelModeLevel = 0;
if (!is_parallel_worker)
{