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, 6 insertions, 7 deletions

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index e16afa0559d..f0cbaefd60e 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.151 2006/07/31 01:16:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.152 2006/07/31 20:09:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -314,8 +314,7 @@ check_index_is_clusterable(Relation OldHeap, Oid indexOid, bool recheck)
 {
 	Relation	OldIndex;
 
-	OldIndex = index_open(indexOid);
-	LockRelation(OldIndex, AccessExclusiveLock);
+	OldIndex = index_open(indexOid, AccessExclusiveLock);
 
 	/*
 	 * Check that index is in fact an index on the given relation
@@ -406,7 +405,7 @@ check_index_is_clusterable(Relation OldHeap, Oid indexOid, bool recheck)
 			   errmsg("cannot cluster temporary tables of other sessions")));
 
 	/* Drop relcache refcnt on OldIndex, but keep lock */
-	index_close(OldIndex);
+	index_close(OldIndex, NoLock);
 }
 
 /*
@@ -649,7 +648,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
 	 */
 	NewHeap = heap_open(OIDNewHeap, AccessExclusiveLock);
 	OldHeap = heap_open(OIDOldHeap, AccessExclusiveLock);
-	OldIndex = index_open(OIDOldIndex);
+	OldIndex = index_open(OIDOldIndex, AccessExclusiveLock);
 
 	/*
 	 * Their tuple descriptors should be exactly alike, but here we only need
@@ -669,7 +668,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
 	 * Scan through the OldHeap on the OldIndex and copy each tuple into the
 	 * NewHeap.
 	 */
-	scan = index_beginscan(OldHeap, OldIndex, true,
+	scan = index_beginscan(OldHeap, OldIndex,
 						   SnapshotNow, 0, (ScanKey) NULL);
 
 	while ((tuple = index_getnext(scan, ForwardScanDirection)) != NULL)
@@ -724,7 +723,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
 	pfree(values);
 	pfree(nulls);
 
-	index_close(OldIndex);
+	index_close(OldIndex, NoLock);
 	heap_close(OldHeap, NoLock);
 	heap_close(NewHeap, NoLock);
 }