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.

3 files changed, 29 insertions, 40 deletions

diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index cffe624deb4..3e1f8f4a68d 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -7,12 +7,13 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteManip.c,v 1.50 2000/10/05 19:11:34 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteManip.c,v 1.51 2000/11/16 22:30:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
+#include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
 #include "optimizer/tlist.h"
 #include "parser/parsetree.h"
@@ -555,20 +556,6 @@ AddNotQual(Query *parsetree, Node *qual)
 }
 
 
-/* Build a NULL constant expression of the given type */
-static Node *
-make_null(Oid type)
-{
-	Const	   *c = makeNode(Const);
-
-	c->consttype = type;
-	c->constlen = get_typlen(type);
-	c->constvalue = PointerGetDatum(NULL);
-	c->constisnull = true;
-	c->constbyval = get_typbyval(type);
-	return (Node *) c;
-}
-
 /* Find a targetlist entry by resno */
 static Node *
 FindMatchingNew(List *tlist, int attno)
@@ -656,7 +643,7 @@ ResolveNew_mutator(Node *node, ResolveNew_context *context)
 				else
 				{
 					/* Otherwise replace unmatched var with a null */
-					return make_null(var->vartype);
+					return (Node *) makeNullConst(var->vartype);
 				}
 			}
 			else
@@ -796,7 +783,7 @@ HandleRIRAttributeRule_mutator(Node *node,
 			{					/* HACK: disallow SET variables */
 				*context->modified = TRUE;
 				*context->badsql = TRUE;
-				return make_null(var->vartype);
+				return (Node *) makeNullConst(var->vartype);
 			}
 			else
 			{
@@ -813,7 +800,7 @@ HandleRIRAttributeRule_mutator(Node *node,
 					n = FindMatchingTLEntry(context->targetlist,
 											name_to_look_for);
 					if (n == NULL)
-						return make_null(var->vartype);
+						return (Node *) makeNullConst(var->vartype);
 					/* Make a copy of the tlist item to return */
 					n = copyObject(n);
 
diff --git a/src/backend/rewrite/rewriteRemove.c b/src/backend/rewrite/rewriteRemove.c
index ba409f4fbf6..760614461cd 100644
--- a/src/backend/rewrite/rewriteRemove.c
+++ b/src/backend/rewrite/rewriteRemove.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteRemove.c,v 1.40 2000/09/29 18:21:24 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteRemove.c,v 1.41 2000/11/16 22:30:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -35,21 +35,26 @@ RewriteGetRuleEventRel(char *rulename)
 {
 	HeapTuple	htup;
 	Oid			eventrel;
+	char	   *result;
 
-	htup = SearchSysCacheTuple(RULENAME,
-							   PointerGetDatum(rulename),
-							   0, 0, 0);
+	htup = SearchSysCache(RULENAME,
+						  PointerGetDatum(rulename),
+						  0, 0, 0);
 	if (!HeapTupleIsValid(htup))
 		elog(ERROR, "Rule or view \"%s\" not found",
 		  ((strncmp(rulename, "_RET", 4) == 0) ? (rulename + 4) : rulename));
 	eventrel = ((Form_pg_rewrite) GETSTRUCT(htup))->ev_class;
-	htup = SearchSysCacheTuple(RELOID,
-							   PointerGetDatum(eventrel),
-							   0, 0, 0);
+	ReleaseSysCache(htup);
+
+	htup = SearchSysCache(RELOID,
+						  PointerGetDatum(eventrel),
+						  0, 0, 0);
 	if (!HeapTupleIsValid(htup))
 		elog(ERROR, "Relation %u not found", eventrel);
 
-	return NameStr(((Form_pg_class) GETSTRUCT(htup))->relname);
+	result = pstrdup(NameStr(((Form_pg_class) GETSTRUCT(htup))->relname));
+	ReleaseSysCache(htup);
+	return result;
 }
 
 /*
@@ -75,9 +80,9 @@ RemoveRewriteRule(char *ruleName)
 	/*
 	 * Find the tuple for the target rule.
 	 */
-	tuple = SearchSysCacheTupleCopy(RULENAME,
-									PointerGetDatum(ruleName),
-									0, 0, 0);
+	tuple = SearchSysCacheCopy(RULENAME,
+							   PointerGetDatum(ruleName),
+							   0, 0, 0);
 
 	/*
 	 * complain if no rule with such name existed
diff --git a/src/backend/rewrite/rewriteSupport.c b/src/backend/rewrite/rewriteSupport.c
index 264021da223..30e4ba6e603 100644
--- a/src/backend/rewrite/rewriteSupport.c
+++ b/src/backend/rewrite/rewriteSupport.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteSupport.c,v 1.44 2000/09/29 18:21:24 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteSupport.c,v 1.45 2000/11/16 22:30:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -18,19 +18,15 @@
 #include "catalog/catname.h"
 #include "catalog/indexing.h"
 #include "rewrite/rewriteSupport.h"
-#include "utils/catcache.h"
 #include "utils/syscache.h"
 
 
-int
+bool
 IsDefinedRewriteRule(char *ruleName)
 {
-	HeapTuple	tuple;
-
-	tuple = SearchSysCacheTuple(RULENAME,
+	return SearchSysCacheExists(RULENAME,
 								PointerGetDatum(ruleName),
 								0, 0, 0);
-	return HeapTupleIsValid(tuple);
 }
 
 /*
@@ -59,10 +55,11 @@ SetRelationRuleStatus(Oid relationId, bool relHasRules,
 	 * Find the tuple to update in pg_class, using syscache for the lookup.
 	 */
 	relationRelation = heap_openr(RelationRelationName, RowExclusiveLock);
-	tuple = SearchSysCacheTupleCopy(RELOID,
-									ObjectIdGetDatum(relationId),
-									0, 0, 0);
-	Assert(HeapTupleIsValid(tuple));
+	tuple = SearchSysCacheCopy(RELOID,
+							   ObjectIdGetDatum(relationId),
+							   0, 0, 0);
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "SetRelationRuleStatus: cache lookup failed for relation %u", relationId);
 
 	/* Do the update */
 	((Form_pg_class) GETSTRUCT(tuple))->relhasrules = relHasRules;