Eliminate a few more user-visible "cache lookup failed" errors.

Michael Paquier

src/backend/utils/adt/ruleutils.c

@@ -2238,11 +2238,11 @@ pg_get_function_arguments(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	HeapTuple	proctup;
 
-	initStringInfo(&buf);
-
 	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(proctup))
-		elog(ERROR, "cache lookup failed for function %u", funcid);
+		PG_RETURN_NULL();
+
+	initStringInfo(&buf);
 
 	(void) print_function_arguments(&buf, proctup, false, true);
 
@@ -2264,11 +2264,11 @@ pg_get_function_identity_arguments(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	HeapTuple	proctup;
 
-	initStringInfo(&buf);
-
 	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(proctup))
-		elog(ERROR, "cache lookup failed for function %u", funcid);
+		PG_RETURN_NULL();
+
+	initStringInfo(&buf);
 
 	(void) print_function_arguments(&buf, proctup, false, false);
 
@@ -2289,11 +2289,11 @@ pg_get_function_result(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	HeapTuple	proctup;
 
-	initStringInfo(&buf);
-
 	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(proctup))
-		elog(ERROR, "cache lookup failed for function %u", funcid);
+		PG_RETURN_NULL();
+
+	initStringInfo(&buf);
 
 	print_function_rettype(&buf, proctup);
 
@@ -2547,7 +2547,7 @@ pg_get_function_arg_default(PG_FUNCTION_ARGS)
 
 	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
 	if (!HeapTupleIsValid(proctup))
-		elog(ERROR, "cache lookup failed for function %u", funcid);
+		PG_RETURN_NULL();
 
 	numargs = get_func_arg_info(proctup, &argtypes, &argnames, &argmodes);
 	if (nth_arg < 1 || nth_arg > numargs || !is_input_argument(nth_arg - 1, argmodes))

src/test/regress/expected/rules.out

@@ -3094,3 +3094,33 @@ SELECT pg_get_viewdef(0);
  
 (1 row)
 
+SELECT pg_get_function_arguments(0);
+ pg_get_function_arguments 
+---------------------------
+ 
+(1 row)
+
+SELECT pg_get_function_identity_arguments(0);
+ pg_get_function_identity_arguments 
+------------------------------------
+ 
+(1 row)
+
+SELECT pg_get_function_result(0);
+ pg_get_function_result 
+------------------------
+ 
+(1 row)
+
+SELECT pg_get_function_arg_default(0, 0);
+ pg_get_function_arg_default 
+-----------------------------
+ 
+(1 row)
+
+SELECT pg_get_function_arg_default('pg_class'::regclass, 0);
+ pg_get_function_arg_default 
+-----------------------------
+ 
+(1 row)
+

src/test/regress/sql/rules.sql

@@ -1152,3 +1152,8 @@ SELECT pg_get_indexdef(0);
 SELECT pg_get_ruledef(0);
 SELECT pg_get_triggerdef(0);
 SELECT pg_get_viewdef(0);
+SELECT pg_get_function_arguments(0);
+SELECT pg_get_function_identity_arguments(0);
+SELECT pg_get_function_result(0);
+SELECT pg_get_function_arg_default(0, 0);
+SELECT pg_get_function_arg_default('pg_class'::regclass, 0);