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.

1 files changed, 22 insertions, 47 deletions

diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 186ecd07f3..33a589ec88 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/aclchk.c,v 1.27 1999/07/30 18:09:44 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/aclchk.c,v 1.28 1999/09/18 19:06:33 tgl Exp $
  *
  * NOTES
  *	  See acl.h.
@@ -105,19 +105,15 @@ ChangeAcl(char *relname,
 	 * We can't use the syscache here, since we need to do a heap_replace on
 	 * the tuple we find.
 	 */
-	relation = heap_openr(RelationRelationName);
-	if (!RelationIsValid(relation))
-		elog(ERROR, "ChangeAcl: could not open '%s'??",
-			 RelationRelationName);
+	relation = heap_openr(RelationRelationName, RowExclusiveLock);
 	tuple = SearchSysCacheTuple(RELNAME,
 								PointerGetDatum(relname),
 								0, 0, 0);
 	if (!HeapTupleIsValid(tuple))
 	{
-		heap_close(relation);
+		heap_close(relation, RowExclusiveLock);
 		elog(ERROR, "ChangeAcl: class \"%s\" not found",
 			 relname);
-		return;
 	}
 
 	if (!heap_attisnull(tuple, Anum_pg_class_relacl))
@@ -164,7 +160,7 @@ ChangeAcl(char *relname,
 	CatalogIndexInsert(idescs, Num_pg_class_indices, relation, tuple);
 	CatalogCloseIndices(Num_pg_class_indices, idescs);
 
-	heap_close(relation);
+	heap_close(relation, RowExclusiveLock);
 	if (free_old_acl)
 		pfree(old_acl);
 	pfree(new_acl);
@@ -213,13 +209,7 @@ in_group(AclId uid, AclId gid)
 	AclId	   *aidp;
 	int32		found = 0;
 
-	relation = heap_openr(GroupRelationName);
-	if (!RelationIsValid(relation))
-	{
-		elog(NOTICE, "in_group: could not open \"%s\"??",
-			 GroupRelationName);
-		return 0;
-	}
+	relation = heap_openr(GroupRelationName, RowExclusiveLock);
 	tuple = SearchSysCacheTuple(GROSYSID,
 								ObjectIdGetDatum(gid),
 								0, 0, 0);
@@ -242,7 +232,7 @@ in_group(AclId uid, AclId gid)
 	}
 	else
 		elog(NOTICE, "in_group: group %d not found", gid);
-	heap_close(relation);
+	heap_close(relation, RowExclusiveLock);
 	return found;
 }
 
@@ -413,6 +403,7 @@ pg_aclcheck(char *relname, char *usename, AclMode mode)
 	}
 
 #ifndef ACLDEBUG
+	relation = heap_openr(RelationRelationName, RowExclusiveLock);
 	tuple = SearchSysCacheTuple(RELNAME,
 								PointerGetDatum(relname),
 								0, 0, 0);
@@ -420,18 +411,15 @@ pg_aclcheck(char *relname, char *usename, AclMode mode)
 	{
 		elog(ERROR, "pg_aclcheck: class \"%s\" not found",
 			 relname);
-		/* an elog(ERROR) kills us, so no need to return anything. */
 	}
 	if (!heap_attisnull(tuple, Anum_pg_class_relacl))
 	{
-		relation = heap_openr(RelationRelationName);
 		tmp = (Acl *) heap_getattr(tuple,
 								   Anum_pg_class_relacl,
 								   RelationGetDescr(relation),
 								   (bool *) NULL);
 		acl = makeacl(ACL_NUM(tmp));
 		memmove((char *) acl, (char *) tmp, ACL_SIZE(tmp));
-		heap_close(relation);
 	}
 	else
 	{
@@ -442,42 +430,29 @@ pg_aclcheck(char *relname, char *usename, AclMode mode)
 		 */
 		int4		ownerId;
 
-		relation = heap_openr(RelationRelationName);
 		ownerId = (int4) heap_getattr(tuple,
 									  Anum_pg_class_relowner,
 									  RelationGetDescr(relation),
 									  (bool *) NULL);
 		acl = aclownerdefault(relname, (AclId) ownerId);
-		heap_close(relation);
 	}
+	heap_close(relation, RowExclusiveLock);
 #else
-	{							/* This is why the syscache is great... */
-		static ScanKeyData relkey[1] = {
-			{0, Anum_pg_class_relname, F_NAMEEQ}
-		};
-
-		relation = heap_openr(RelationRelationName);
-		if (!RelationIsValid(relation))
-		{
-			elog(NOTICE, "pg_checkacl: could not open \"%-.*s\"??",
-				 RelationRelationName);
-			return ACLCHECK_NO_CLASS;
-		}
-		tuple = SearchSysCacheTuple(RELNAME,
-									PointerGetDatum(relname),
-									0, 0, 0);
-		if (HeapTupleIsValid(tuple) &&
-			!heap_attisnull(tuple, Anum_pg_class_relacl))
-		{
-			tmp = (Acl *) heap_getattr(tuple,
-									   Anum_pg_class_relacl,
-									   RelationGetDescr(relation),
-									   (bool *) NULL);
-			acl = makeacl(ACL_NUM(tmp));
-			memmove((char *) acl, (char *) tmp, ACL_SIZE(tmp));
-		}
-		heap_close(relation);
+	relation = heap_openr(RelationRelationName, RowExclusiveLock);
+	tuple = SearchSysCacheTuple(RELNAME,
+								PointerGetDatum(relname),
+								0, 0, 0);
+	if (HeapTupleIsValid(tuple) &&
+		!heap_attisnull(tuple, Anum_pg_class_relacl))
+	{
+		tmp = (Acl *) heap_getattr(tuple,
+								   Anum_pg_class_relacl,
+								   RelationGetDescr(relation),
+								   (bool *) NULL);
+		acl = makeacl(ACL_NUM(tmp));
+		memmove((char *) acl, (char *) tmp, ACL_SIZE(tmp));
 	}
+	heap_close(relation, RowExclusiveLock);
 #endif
 	result = aclcheck(relname, acl, id, (AclIdType) ACL_IDTYPE_UID, mode);
 	if (acl)