database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-16 06:01:02 +03:00
Code Activity

Now that we've rearranged relation open to get a lock before touching

Browse Source 
the rel, it's easy to get rid of the narrow race-condition window that
used to exist in VACUUM and CLUSTER.  Did some minor code-beautification
work in the same area, too.
This commit is contained in:
Tom Lane
2006-08-18 16:09:13 +00:00
parent e91600d1c2
commit 7aa772f03e
8 changed files with 153 additions and 91 deletions
Download Patch File Download Diff File Expand all files Collapse all files

86
src/backend/access/heap/heapam.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.218 2006/07/31 20:08:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.219 2006/08/18 16:09:08 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -53,6 +53,7 @@
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/relcache.h"
#include "utils/syscache.h"
static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@ -702,14 +703,56 @@ relation_open(Oid relationId, LOCKMODE lockmode)
}
/* ----------------
* conditional_relation_open - open with option not to wait
* try_relation_open - open any relation by relation OID
*
* As above, but if nowait is true, then throw an error rather than
* waiting when the lock is not immediately obtainable.
* Same as relation_open, except return NULL instead of failing
* if the relation does not exist.
* ----------------
*/
Relation
conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
try_relation_open(Oid relationId, LOCKMODE lockmode)
{
Relation r;
Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
/* Get the lock first */
if (lockmode != NoLock)
LockRelationOid(relationId, lockmode);
/*
* Now that we have the lock, probe to see if the relation really
* exists or not.
*/
if (!SearchSysCacheExists(RELOID,
ObjectIdGetDatum(relationId),
0, 0, 0))
{
/* Release useless lock */
if (lockmode != NoLock)
UnlockRelationOid(relationId, lockmode);
return NULL;
}
/* Should be safe to do a relcache load */
r = RelationIdGetRelation(relationId);
if (!RelationIsValid(r))
elog(ERROR, "could not open relation with OID %u", relationId);
return r;
}
/* ----------------
* relation_open_nowait - open but don't wait for lock
*
* Same as relation_open, except throw an error instead of waiting
* when the requested lock is not immediately obtainable.
* ----------------
*/
Relation
relation_open_nowait(Oid relationId, LOCKMODE lockmode)
{
Relation r;
@ -718,27 +761,22 @@ conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
/* Get the lock before trying to open the relcache entry */
if (lockmode != NoLock)
{
if (nowait)
if (!ConditionalLockRelationOid(relationId, lockmode))
{
if (!ConditionalLockRelationOid(relationId, lockmode))
{
/* try to throw error by name; relation could be deleted... */
char *relname = get_rel_name(relationId);
/* try to throw error by name; relation could be deleted... */
char *relname = get_rel_name(relationId);
if (relname)
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s\"",
relname)));
else
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation with OID %u",
relationId)));
}
if (relname)
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s\"",
relname)));
else
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation with OID %u",
relationId)));
}
else
LockRelationOid(relationId, lockmode);
}
/* The relcache does all the real work... */
@ -753,7 +791,7 @@ conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
/* ----------------
* relation_openrv - open any relation specified by a RangeVar
*
* As above, but the relation is specified by a RangeVar.
* Same as relation_open, but the relation is specified by a RangeVar.
* ----------------
*/
Relation