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

Michael Paquier

Original Postgres commit:
https://github.com/postgres/postgres/commit/3153b1a52f8f2d1efe67306257aec15aaaf9e94c

src/backend/utils/adt/ruleutils.c

@@ -2317,11 +2317,11 @@ 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);
 
@@ -2343,11 +2343,11 @@ 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);
 
@@ -2368,11 +2368,11 @@ 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);
 
@@ -2602,7 +2602,7 @@ 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

@@ -2772,6 +2772,36 @@ 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)
+
 -- test rule for select-for-update
 create table t_test_rules_select_for_update (c int) distributed randomly;
 create rule myrule as on insert to t_test_rules_select_for_update

src/test/regress/sql/rules.sql

@@ -1043,6 +1043,11 @@ 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);
 
 -- test rule for select-for-update
 create table t_test_rules_select_for_update (c int) distributed randomly;