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| author | Andres Freund <andres@anarazel.de> | 2015-12-14 11:34:16 +0100 |
|---|---|---|
| committer | Andres Freund <andres@anarazel.de> | 2015-12-14 11:34:50 +0100 |
| commit | ccde00b9b97ed8b7307e39f95bd48922bf955bb2 (patch) | |
| tree | 1222e0dc24497adb33f8bbf9cb71f45e355215ab | |
| parent | cb89644bb0df1921c6a15aa294903a9458c2a67d (diff) | |
| download | postgresql-ccde00b9b97ed8b7307e39f95bd48922bf955bb2.tar.gz | |
Fix bug in SetOffsetVacuumLimit() triggered by find_multixact_start() failure.
Previously, if find_multixact_start() failed, SetOffsetVacuumLimit() would
install 0 into MultiXactState->offsetStopLimit if it previously succeeded.
Luckily, there are no known cases where find_multixact_start() will return
an error in 9.5 and above. But if it were to happen, for example due to
filesystem permission issues, it'd be somewhat bad: GetNewMultiXactId()
could continue allocating mxids even if close to a wraparound, or it could
erroneously stop allocating mxids, even if no wraparound is looming. The
wrong value would be corrected the next time SetOffsetVacuumLimit() is
called, or by a restart.
Reported-By: Noah Misch, although this is not his preferred fix
Discussion: 20151210140450.GA22278@alap3.anarazel.de
Backpatch: 9.5, where the bug was introduced as part of 4f627f
| -rw-r--r-- | src/backend/access/transam/multixact.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index c886ec3228..c730fc49c5 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -2552,6 +2552,7 @@ SetOffsetVacuumLimit(void) bool oldestOffsetKnown = false; bool prevOldestOffsetKnown; MultiXactOffset offsetStopLimit = 0; + MultiXactOffset prevOffsetStopLimit; /* * NB: Have to prevent concurrent truncation, we might otherwise try to @@ -2566,6 +2567,7 @@ SetOffsetVacuumLimit(void) nextOffset = MultiXactState->nextOffset; prevOldestOffsetKnown = MultiXactState->oldestOffsetKnown; prevOldestOffset = MultiXactState->oldestOffset; + prevOffsetStopLimit = MultiXactState->offsetStopLimit; Assert(MultiXactState->finishedStartup); LWLockRelease(MultiXactGenLock); @@ -2633,11 +2635,13 @@ SetOffsetVacuumLimit(void) { /* * If we failed to get the oldest offset this time, but we have a - * value from a previous pass through this function, use the old value - * rather than automatically forcing it. + * value from a previous pass through this function, use the old + * values rather than automatically forcing an emergency autovacuum + * cycle again. */ oldestOffset = prevOldestOffset; oldestOffsetKnown = true; + offsetStopLimit = prevOffsetStopLimit; } /* Install the computed values */ |