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Fix bug in early startup of Hot Standby with subtransactions.

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When HS startup is deferred because of overflowed subtransactions, ensure
that we re-initialize KnownAssignedXids for when both existing and incoming
snapshots have non-zero qualifying xids.

Fixes bug #6661 reported by Valentine Gogichashvili.

Analysis and fix by Andres Freund
This commit is contained in:
Simon Riggs 2012-06-08 17:34:04 +01:00
parent 3b5548a3d5
commit 3725570539
1 changed files with 31 additions and 1 deletions
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32
src/backend/storage/ipc/procarray.c
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@ -160,6 +160,7 @@ static int KnownAssignedXidsGetAndSetXmin(TransactionId *xarray,
TransactionId xmax);
static TransactionId KnownAssignedXidsGetOldestXmin(void);
static void KnownAssignedXidsDisplay(int trace_level);
static void KnownAssignedXidsReset(void);
/*
* Report shared-memory space needed by CreateSharedProcArray.
@ -526,6 +527,11 @@ ProcArrayApplyRecoveryInfo(RunningTransactions running)
*/
if (!running->subxid_overflow || running->xcnt == 0)
{
/*
* If we have already collected known assigned xids, we need to
* throw them away before we apply the recovery snapshot.
*/
KnownAssignedXidsReset();
standbyState = STANDBY_INITIALIZED;
}
else
@ -569,7 +575,6 @@ ProcArrayApplyRecoveryInfo(RunningTransactions running)
* xids to subtrans. If RunningXacts is overflowed then we don't have
* enough information to correctly update subtrans anyway.
*/
Assert(procArray->numKnownAssignedXids == 0);
/*
* Allocate a temporary array to avoid modifying the array passed as
@ -599,6 +604,12 @@ ProcArrayApplyRecoveryInfo(RunningTransactions running)
if (nxids > 0)
{
if (procArray->numKnownAssignedXids != 0)
{
LWLockRelease(ProcArrayLock);
elog(ERROR, "KnownAssignedXids is not empty");
}
/*
* Sort the array so that we can add them safely into
* KnownAssignedXids.
@ -3340,3 +3351,22 @@ KnownAssignedXidsDisplay(int trace_level)
pfree(buf.data);
}
/*
* KnownAssignedXidsReset
* Resets KnownAssignedXids to be empty
*/
static void
KnownAssignedXidsReset(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile ProcArrayStruct *pArray = procArray;
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
pArray->numKnownAssignedXids = 0;
pArray->tailKnownAssignedXids = 0;
pArray->headKnownAssignedXids = 0;
LWLockRelease(ProcArrayLock);
}