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Add NOWAIT option to SELECT FOR UPDATE/SHARE.

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Original patch by Hans-Juergen Schoenig, revisions by Karel Zak
and Tom Lane.
This commit is contained in:
Tom Lane
2005-08-01 20:31:16 +00:00
parent ca7abcd89d
commit 2a4fad1a0e
28 changed files with 387 additions and 157 deletions
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61
src/backend/storage/lmgr/lmgr.c
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@@ -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 $
*
*-------------------------------------------------------------------------
*/
@@ -368,6 +368,27 @@ LockTuple(Relation relation, ItemPointer tid, LOCKMODE lockmode)
lockmode, false, false);
}
/*
* 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
*/
@@ -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