Allow callers to pass a missing_ok flag when opening a relation.

Since the names try_relation_openrv() and try_heap_openrv() don't seem
quite appropriate, rename the functions to relation_openrv_extended()
and heap_openrv_extended().  This is also more general, if we have a
future need for additional parameters that are of interest to only a
few callers.

This is infrastructure for a forthcoming patch to allow
get_object_address() to take a missing_ok argument as well.

Patch by me, review by Noah Misch.

src/backend/access/heap/heapam.c

@@ -1004,15 +1004,17 @@ relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
 }
 
 /* ----------------
- *		try_relation_openrv - open any relation specified by a RangeVar
+ *		relation_openrv_extended - open any relation specified by a RangeVar
  *
- *		Same as relation_openrv, but return NULL instead of failing for
- *		relation-not-found.  (Note that some other causes, such as
- *		permissions problems, will still result in an ereport.)
+ *		Same as relation_openrv, but with an additional missing_ok argument
+ *		allowing a NULL return rather than an error if the relation is not
+ *      found.  (Note that some other causes, such as permissions problems,
+ *      will still result in an ereport.)
  * ----------------
  */
 Relation
-try_relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
+relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
+						 bool missing_ok)
 {
 	Oid			relOid;
 
@@ -1032,7 +1034,7 @@ try_relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
 		AcceptInvalidationMessages();
 
 	/* Look up the appropriate relation using namespace search */
-	relOid = RangeVarGetRelid(relation, true);
+	relOid = RangeVarGetRelid(relation, missing_ok);
 
 	/* Return NULL on not-found */
 	if (!OidIsValid(relOid))
@@ -1125,18 +1127,20 @@ heap_openrv(const RangeVar *relation, LOCKMODE lockmode)
 }
 
 /* ----------------
- *		try_heap_openrv - open a heap relation specified
+ *		heap_openrv_extended - open a heap relation specified
  *		by a RangeVar node
  *
- *		As above, but return NULL instead of failing for relation-not-found.
+ *		As above, but optionally return NULL instead of failing for
+ *      relation-not-found.
  * ----------------
  */
 Relation
-try_heap_openrv(const RangeVar *relation, LOCKMODE lockmode)
+heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
+					 bool missing_ok)
 {
 	Relation	r;
 
-	r = try_relation_openrv(relation, lockmode);
+	r = relation_openrv_extended(relation, lockmode, missing_ok);
 
 	if (r)
 	{

src/backend/parser/parse_relation.c

@@ -826,7 +826,7 @@ parserOpenTable(ParseState *pstate, const RangeVar *relation, int lockmode)
 	ParseCallbackState pcbstate;
 
 	setup_parser_errposition_callback(&pcbstate, pstate, relation->location);
-	rel = try_heap_openrv(relation, lockmode);
+	rel = heap_openrv_extended(relation, lockmode, true);
 	if (rel == NULL)
 	{
 		if (relation->schemaname)

src/include/access/heapam.h

@@ -50,12 +50,14 @@ typedef enum
 extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
 extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
 extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
-extern Relation try_relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
+extern Relation relation_openrv_extended(const RangeVar *relation,
+						 LOCKMODE lockmode, bool missing_ok);
 extern void relation_close(Relation relation, LOCKMODE lockmode);
 
 extern Relation heap_open(Oid relationId, LOCKMODE lockmode);
 extern Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
-extern Relation try_heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
+extern Relation heap_openrv_extended(const RangeVar *relation,
+					 LOCKMODE lockmode, bool missing_ok);
 
 #define heap_close(r,l)  relation_close(r,l)
 

src/pl/tcl/pltcl.c

@@ -493,8 +493,8 @@ pltcl_init_load_unknown(Tcl_Interp *interp)
 	 * This is for backwards compatibility.  To ensure that the table
 	 * is trustworthy, we require it to be owned by a superuser.
 	 ************************************************************/
-	pmrel = try_relation_openrv(makeRangeVar(NULL, "pltcl_modules", -1),
-								AccessShareLock);
+	pmrel = relation_openrv_extended(makeRangeVar(NULL, "pltcl_modules", -1),
+									 AccessShareLock, true);
 	if (pmrel == NULL)
 		return;
 	/* must be table or view, else ignore */