Change SearchSysCache coding conventions so that a reference count is

maintained for each cache entry.  A cache entry will not be freed until
the matching ReleaseSysCache call has been executed.  This eliminates
worries about cache entries getting dropped while still in use.  See
my posting to pg-hackers of even date for more info.

1 files changed, 18 insertions, 17 deletions

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 6611f134727..77f7776f6d9 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.70 2000/10/03 03:11:13 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.71 2000/11/16 22:30:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -193,9 +193,7 @@ void
 Async_Listen(char *relname, int pid)
 {
 	Relation	lRel;
-	TupleDesc	tdesc;
-	HeapTuple	tuple,
-				newtup;
+	HeapTuple	tuple;
 	Datum		values[Natts_pg_listener];
 	char		nulls[Natts_pg_listener];
 	int			i;
@@ -205,13 +203,12 @@ Async_Listen(char *relname, int pid)
 		elog(DEBUG, "Async_Listen: %s", relname);
 
 	lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
-	tdesc = RelationGetDescr(lRel);
 
 	/* Detect whether we are already listening on this relname */
-	tuple = SearchSysCacheTuple(LISTENREL, Int32GetDatum(pid),
-								PointerGetDatum(relname),
-								0, 0);
-	if (tuple != NULL)
+	if (SearchSysCacheExists(LISTENREL,
+							 Int32GetDatum(pid),
+							 PointerGetDatum(relname),
+							 0, 0))
 	{
 		/* No need to scan the rest of the table */
 		heap_close(lRel, AccessExclusiveLock);
@@ -235,18 +232,18 @@ Async_Listen(char *relname, int pid)
 	values[i++] = (Datum) 0;	/* no notifies pending */
 
 	tupDesc = lRel->rd_att;
-	newtup = heap_formtuple(tupDesc, values, nulls);
-	heap_insert(lRel, newtup);
+	tuple = heap_formtuple(tupDesc, values, nulls);
+	heap_insert(lRel, tuple);
 	if (RelationGetForm(lRel)->relhasindex)
 	{
 		Relation	idescs[Num_pg_listener_indices];
 
 		CatalogOpenIndices(Num_pg_listener_indices, Name_pg_listener_indices, idescs);
-		CatalogIndexInsert(idescs, Num_pg_listener_indices, lRel, newtup);
+		CatalogIndexInsert(idescs, Num_pg_listener_indices, lRel, tuple);
 		CatalogCloseIndices(Num_pg_listener_indices, idescs);
 	}
 
-	heap_freetuple(newtup);
+	heap_freetuple(tuple);
 
 	heap_close(lRel, AccessExclusiveLock);
 
@@ -296,11 +293,15 @@ Async_Unlisten(char *relname, int pid)
 
 	lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
 	/* Note we assume there can be only one matching tuple. */
-	lTuple = SearchSysCacheTuple(LISTENREL, Int32GetDatum(pid),
-								PointerGetDatum(relname),
-								0, 0);
-	if (lTuple != NULL)
+	lTuple = SearchSysCache(LISTENREL,
+							Int32GetDatum(pid),
+							PointerGetDatum(relname),
+							0, 0);
+	if (HeapTupleIsValid(lTuple))
+	{
 		heap_delete(lRel, &lTuple->t_self, NULL);
+		ReleaseSysCache(lTuple);
+	}
 	heap_close(lRel, AccessExclusiveLock);
 
 	/*