Mega-commit to make heap_open/heap_openr/heap_close take an

additional argument specifying the kind of lock to acquire/release (or
'NoLock' to do no lock processing).  Ensure that all relations are locked
with some appropriate lock level before being examined --- this ensures
that relevant shared-inval messages have been processed and should prevent
problems caused by concurrent VACUUM.  Fix several bugs having to do with
mismatched increment/decrement of relation ref count and mismatched
heap_open/close (which amounts to the same thing).  A bogus ref count on
a relation doesn't matter much *unless* a SI Inval message happens to
arrive at the wrong time, which is probably why we got away with this
sloppiness for so long.  Repair missing grab of AccessExclusiveLock in
DROP TABLE, ALTER/RENAME TABLE, etc, as noted by Hiroshi.
Recommend 'make clean all' after pulling this update; I modified the
Relation struct layout slightly.
Will post further discussion to pghackers list shortly.

2 files changed, 16 insertions, 5 deletions

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index de0d803efe..b435dd53ca 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.61 1999/07/17 20:17:40 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.62 1999/09/18 19:07:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -109,7 +109,7 @@ RelationGetBufferWithBuffer(Relation relation,
 	{
 		if (!BufferIsLocal(buffer))
 		{
-			LockRelId  *lrelId = &(((LockInfo) (relation->lockInfo))->lockRelId);
+			LockRelId  *lrelId = & relation->rd_lockInfo.lockRelId;
 
 			bufHdr = &BufferDescriptors[buffer - 1];
 			SpinAcquire(BufMgrLock);
@@ -813,6 +813,7 @@ FlushBuffer(Buffer buffer, bool release)
 	status = smgrflush(DEFAULT_SMGR, bufrel, bufHdr->tag.blockNum,
 					   (char *) MAKE_PTR(bufHdr->data));
 
+	/* drop relcache refcount incremented by RelationIdCacheGetRelation */
 	RelationDecrementReferenceCount(bufrel);
 
 	if (status == SM_FAIL)
@@ -993,6 +994,7 @@ BufferSync()
 						elog(ERROR, "BufferSync: write error %u for %s",
 							 bufHdr->tag.blockNum, bufHdr->sb_relname);
 					}
+					/* drop refcount from RelationIdCacheGetRelation */
 					if (reln != (Relation) NULL)
 						RelationDecrementReferenceCount(reln);
 					continue;
@@ -1047,6 +1049,7 @@ BufferSync()
 				 */
 				if (!(bufHdr->flags & BM_JUST_DIRTIED))
 					bufHdr->flags &= ~BM_DIRTY;
+				/* drop refcount from RelationIdCacheGetRelation */
 				if (reln != (Relation) NULL)
 					RelationDecrementReferenceCount(reln);
 			}
@@ -1282,14 +1285,16 @@ BufferGetRelation(Buffer buffer)
 	/* XXX should be a critical section */
 	relid = BufferDescriptors[buffer - 1].tag.relId.relId;
 	relation = RelationIdGetRelation(relid);
+	Assert(relation);
 
+	/* drop relcache refcount incremented by RelationIdGetRelation */
 	RelationDecrementReferenceCount(relation);
 
 	if (RelationHasReferenceCountZero(relation))
 	{
 
 		/*
-		 * elog(NOTICE, "BufferGetRelation: 0->1");
+		 * XXX why??
 		 */
 
 		RelationIncrementReferenceCount(relation);
@@ -1342,7 +1347,6 @@ BufferReplace(BufferDesc *bufHdr, bool bufferLockHeld)
 	}
 	else
 	{
-
 		/* blind write always flushes */
 		status = smgrblindwrt(DEFAULT_SMGR, bufHdr->sb_dbname,
 							  bufHdr->sb_relname, bufdb, bufrel,
@@ -1350,6 +1354,7 @@ BufferReplace(BufferDesc *bufHdr, bool bufferLockHeld)
 							  (char *) MAKE_PTR(bufHdr->data));
 	}
 
+	/* drop relcache refcount incremented by RelationIdCacheGetRelation */
 	if (reln != (Relation) NULL)
 		RelationDecrementReferenceCount(reln);
 
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
index a6a2d456b2..e003595bed 100644
--- a/src/backend/storage/buffer/localbuf.c
+++ b/src/backend/storage/buffer/localbuf.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/localbuf.c,v 1.26 1999/07/17 20:17:41 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/buffer/localbuf.c,v 1.27 1999/09/18 19:07:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -109,6 +109,8 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
 		smgrwrite(DEFAULT_SMGR, bufrel, bufHdr->tag.blockNum,
 				  (char *) MAKE_PTR(bufHdr->data));
 		LocalBufferFlushCount++;
+
+		/* drop relcache refcount incremented by RelationIdCacheGetRelation */
 		RelationDecrementReferenceCount(bufrel);
 	}
 
@@ -187,6 +189,8 @@ FlushLocalBuffer(Buffer buffer, bool release)
 	smgrflush(DEFAULT_SMGR, bufrel, bufHdr->tag.blockNum,
 			  (char *) MAKE_PTR(bufHdr->data));
 	LocalBufferFlushCount++;
+
+	/* drop relcache refcount incremented by RelationIdCacheGetRelation */
 	RelationDecrementReferenceCount(bufrel);
 
 	Assert(LocalRefCount[bufid] > 0);
@@ -260,6 +264,8 @@ LocalBufferSync(void)
 			smgrwrite(DEFAULT_SMGR, bufrel, buf->tag.blockNum,
 					  (char *) MAKE_PTR(buf->data));
 			LocalBufferFlushCount++;
+
+			/* drop relcache refcount from RelationIdCacheGetRelation */
 			RelationDecrementReferenceCount(bufrel);
 
 			buf->tag.relId.relId = InvalidOid;