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, 15 insertions, 16 deletions

diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 35f3d6da0b3..493d2a170e1 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -6,7 +6,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.87 1999/09/11 22:28:11 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.88 1999/09/18 19:06:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -251,22 +251,22 @@ DoCopy(char *relname, bool binary, bool oids, bool from, bool pipe,
 	Relation	rel;
 	extern char *UserName;		/* defined in global.c */
 	const AclMode required_access = from ? ACL_WR : ACL_RD;
+	LOCKMODE	required_lock = from ? AccessExclusiveLock : AccessShareLock;
+	/* Note: AccessExclusive is probably overkill for copying to a relation,
+	 * but that's what the existing code grabs on the rel's indices.  If
+	 * this is relaxed then I think the index locks need relaxed also.
+	 */
 	int			result;
 
-	rel = heap_openr(relname);
-	if (rel == NULL)
-		elog(ERROR, "COPY command failed.  Class %s "
-			 "does not exist.", relname);
+	rel = heap_openr(relname, required_lock);
 
 	result = pg_aclcheck(relname, UserName, required_access);
 	if (result != ACLCHECK_OK)
 		elog(ERROR, "%s: %s", relname, aclcheck_error_strings[result]);
-	/* Above should not return */
-	else if (!superuser() && !pipe)
+	else if (!pipe && !superuser())
 		elog(ERROR, "You must have Postgres superuser privilege to do a COPY "
 			 "directly to or from a file.  Anyone can COPY to stdout or "
 			 "from stdin.  Psql's \\copy command also works for anyone.");
-	/* Above should not return. */
 	else
 	{
 		if (from)
@@ -342,6 +342,8 @@ DoCopy(char *relname, bool binary, bool oids, bool from, bool pipe,
 				pq_endcopyout(false);
 		}
 	}
+
+	heap_close(rel, required_lock);
 }
 
 
@@ -500,8 +502,6 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim)
 		pfree(elements);
 		pfree(typmod);
 	}
-
-	heap_close(rel);
 }
 
 static void
@@ -905,20 +905,19 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, char *delim)
 		pfree(typmod);
 	}
 
-	/* comments in execUtils.c */
 	if (has_index)
 	{
 		for (i = 0; i < n_indices; i++)
 		{
 			if (index_rels[i] == NULL)
 				continue;
+			/* see comments in ExecOpenIndices() in execUtils.c */
 			if ((index_rels[i])->rd_rel->relam != BTREE_AM_OID &&
 				(index_rels[i])->rd_rel->relam != HASH_AM_OID)
 				UnlockRelation(index_rels[i], AccessExclusiveLock);
 			index_close(index_rels[i]);
 		}
 	}
-	heap_close(rel);
 }
 
 
@@ -991,7 +990,7 @@ IsTypeByVal(Oid type)
 /*
  * Given the OID of a relation, return an array of index relation descriptors
  * and the number of index relations.  These relation descriptors are open
- * using heap_open().
+ * using index_open().
  *
  * Space for the array itself is palloc'ed.
  */
@@ -1017,7 +1016,7 @@ GetIndexRelations(Oid main_relation_oid,
 	int			i;
 	bool		isnull;
 
-	pg_index_rel = heap_openr(IndexRelationName);
+	pg_index_rel = heap_openr(IndexRelationName, AccessShareLock);
 	scandesc = heap_beginscan(pg_index_rel, 0, SnapshotNow, 0, NULL);
 	tupDesc = RelationGetDescr(pg_index_rel);
 
@@ -1044,7 +1043,7 @@ GetIndexRelations(Oid main_relation_oid,
 	}
 
 	heap_endscan(scandesc);
-	heap_close(pg_index_rel);
+	heap_close(pg_index_rel, AccessShareLock);
 
 	/* We cannot trust to relhasindex of the main_relation now, so... */
 	if (*n_indices == 0)
@@ -1055,7 +1054,7 @@ GetIndexRelations(Oid main_relation_oid,
 	for (i = 0, scan = head; i < *n_indices; i++, scan = scan->next)
 	{
 		(*index_rels)[i] = index_open(scan->index_rel_oid);
-		/* comments in execUtils.c */
+		/* see comments in ExecOpenIndices() in execUtils.c */
 		if ((*index_rels)[i] != NULL &&
 			((*index_rels)[i])->rd_rel->relam != BTREE_AM_OID &&
 			((*index_rels)[i])->rd_rel->relam != HASH_AM_OID)