diff options
Diffstat (limited to 'src/backend/storage/lmgr/lmgr.c')
| -rw-r--r-- | src/backend/storage/lmgr/lmgr.c | 61 |
1 files changed, 60 insertions, 1 deletions
diff --git a/src/backend/storage/lmgr/lmgr.c b/src/backend/storage/lmgr/lmgr.c index 91afd4ed9a5..7a4ef9f7554 100644 --- a/src/backend/storage/lmgr/lmgr.c +++ b/src/backend/storage/lmgr/lmgr.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.77 2005/06/17 22:32:45 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.78 2005/08/01 20:31:11 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -369,6 +369,27 @@ LockTuple(Relation relation, ItemPointer tid, LOCKMODE lockmode) } /* + * ConditionalLockTuple + * + * As above, but only lock if we can get the lock without blocking. + * Returns TRUE iff the lock was acquired. + */ +bool +ConditionalLockTuple(Relation relation, ItemPointer tid, LOCKMODE lockmode) +{ + LOCKTAG tag; + + SET_LOCKTAG_TUPLE(tag, + relation->rd_lockInfo.lockRelId.dbId, + relation->rd_lockInfo.lockRelId.relId, + ItemPointerGetBlockNumber(tid), + ItemPointerGetOffsetNumber(tid)); + + return (LockAcquire(LockTableId, &tag, relation->rd_istemp, + lockmode, false, true) != LOCKACQUIRE_NOT_AVAIL); +} + +/* * UnlockTuple */ void @@ -463,6 +484,44 @@ XactLockTableWait(TransactionId xid) TransactionIdAbort(xid); } +/* + * ConditionalXactLockTableWait + * + * As above, but only lock if we can get the lock without blocking. + * Returns TRUE if the lock was acquired. + */ +bool +ConditionalXactLockTableWait(TransactionId xid) +{ + LOCKTAG tag; + + for (;;) + { + Assert(TransactionIdIsValid(xid)); + Assert(!TransactionIdEquals(xid, GetTopTransactionId())); + + SET_LOCKTAG_TRANSACTION(tag, xid); + + if (LockAcquire(LockTableId, &tag, false, + ShareLock, false, true) == LOCKACQUIRE_NOT_AVAIL) + return false; + + LockRelease(LockTableId, &tag, ShareLock, false); + + if (!TransactionIdIsInProgress(xid)) + break; + xid = SubTransGetParent(xid); + } + + /* + * Transaction was committed/aborted/crashed - we have to update + * pg_clog if transaction is still marked as running. + */ + if (!TransactionIdDidCommit(xid) && !TransactionIdDidAbort(xid)) + TransactionIdAbort(xid); + + return true; +} /* * LockDatabaseObject |