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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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41
src/backend/access/transam/multixact.c
View File

@@ -42,7 +42,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.5 2005/06/08 15:50:25 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/multixact.c,v 1.6 2005/08/01 20:31:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -558,6 +558,43 @@ MultiXactIdWait(MultiXactId multi)
}
}
/*
* ConditionalMultiXactIdWait
* As above, but only lock if we can get the lock without blocking.
*/
bool
ConditionalMultiXactIdWait(MultiXactId multi)
{
bool result = true;
TransactionId *members;
int nmembers;
nmembers = GetMultiXactIdMembers(multi, &members);
if (nmembers >= 0)
{
int i;
for (i = 0; i < nmembers; i++)
{
TransactionId member = members[i];
debug_elog4(DEBUG2, "ConditionalMultiXactIdWait: trying %d (%u)",
i, member);
if (!TransactionIdIsCurrentTransactionId(member))
{
result = ConditionalXactLockTableWait(member);
if (!result)
break;
}
}
pfree(members);
}
return result;
}
/*
* CreateMultiXactId
* Make a new MultiXactId
@@ -590,7 +627,7 @@ CreateMultiXactId(int nxids, TransactionId *xids)
*/
multi = mXactCacheGetBySet(nxids, xids);
if (MultiXactIdIsValid(multi))
{
{
debug_elog2(DEBUG2, "Create: in cache!");
return multi;
}