diff options
Diffstat (limited to 'src/backend/access/transam/varsup.c')
| -rw-r--r-- | src/backend/access/transam/varsup.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c index 42fc351f7bf..5efbfbd3d61 100644 --- a/src/backend/access/transam/varsup.c +++ b/src/backend/access/transam/varsup.c @@ -259,7 +259,28 @@ ReadNewTransactionId(void) } /* - * Determine the last safe XID to allocate given the currently oldest + * Advance the cluster-wide value for the oldest valid clog entry. + * + * We must acquire CLogTruncationLock to advance the oldestClogXid. It's not + * necessary to hold the lock during the actual clog truncation, only when we + * advance the limit, as code looking up arbitrary xids is required to hold + * CLogTruncationLock from when it tests oldestClogXid through to when it + * completes the clog lookup. + */ +void +AdvanceOldestClogXid(TransactionId oldest_datfrozenxid) +{ + LWLockAcquire(CLogTruncationLock, LW_EXCLUSIVE); + if (TransactionIdPrecedes(ShmemVariableCache->oldestClogXid, + oldest_datfrozenxid)) + { + ShmemVariableCache->oldestClogXid = oldest_datfrozenxid; + } + LWLockRelease(CLogTruncationLock); +} + +/* + * Determine the last safe XID to allocate using the currently oldest * datfrozenxid (ie, the oldest XID that might exist in any database * of our cluster), and the OID of the (or a) database with that value. */ |