Change the relation_open protocol so that we obtain lock on a relation

(table or index) before trying to open its relcache entry.  This fixes
race conditions in which someone else commits a change to the relation's
catalog entries while we are in process of doing relcache load.  Problems
of that ilk have been reported sporadically for years, but it was not
really practical to fix until recently --- for instance, the recent
addition of WAL-log support for in-place updates helped.

Along the way, remove pg_am.amconcurrent: all AMs are now expected to support
concurrent update.

1 files changed, 3 insertions, 8 deletions

diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index a0bc2869c00..10049d593a0 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.169 2006/07/24 16:32:45 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.170 2006/07/31 20:09:05 tgl Exp $
  *
  * NOTES
  *	  A lock table is a shared memory hash table.  When
@@ -36,6 +36,7 @@
 #include "access/twophase.h"
 #include "access/twophase_rmgr.h"
 #include "miscadmin.h"
+#include "storage/lmgr.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
 #include "utils/resowner.h"
@@ -449,8 +450,6 @@ ProcLockHashCode(const PROCLOCKTAG *proclocktag, uint32 hashcode)
  *
  * Inputs:
  *	locktag: unique identifier for the lockable object
- *	isTempObject: is the lockable object a temporary object?  (Under 2PC,
- *		such locks cannot be persisted)
  *	lockmode: lock mode to acquire
  *	sessionLock: if true, acquire lock for session not current transaction
  *	dontWait: if true, don't wait to acquire lock
@@ -471,7 +470,6 @@ ProcLockHashCode(const PROCLOCKTAG *proclocktag, uint32 hashcode)
  */
 LockAcquireResult
 LockAcquire(const LOCKTAG *locktag,
-			bool isTempObject,
 			LOCKMODE lockmode,
 			bool sessionLock,
 			bool dontWait)
@@ -528,7 +526,6 @@ LockAcquire(const LOCKTAG *locktag,
 	{
 		locallock->lock = NULL;
 		locallock->proclock = NULL;
-		locallock->isTempObject = isTempObject;
 		locallock->hashcode = LockTagHashCode(&(localtag.lock));
 		locallock->nLocks = 0;
 		locallock->numLockOwners = 0;
@@ -540,8 +537,6 @@ LockAcquire(const LOCKTAG *locktag,
 	}
 	else
 	{
-		Assert(locallock->isTempObject == isTempObject);
-
 		/* Make sure there will be room to remember the lock */
 		if (locallock->numLockOwners >= locallock->maxLockOwners)
 		{
@@ -1733,7 +1728,7 @@ AtPrepare_Locks(void)
 		}
 
 		/* Can't handle it if the lock is on a temporary object */
-		if (locallock->isTempObject)
+		if (LockTagIsTemp(&locallock->tag.lock))
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("cannot PREPARE a transaction that has operated on temporary tables")));