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

@@ -1540,13 +1540,13 @@ pg_get_function_arguments(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	HeapTuple	proctup;
 
-	initStringInfo(&buf);
-
 	proctup = SearchSysCache(PROCOID,
 							 ObjectIdGetDatum(funcid),
 							 0, 0, 0);
 	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);
 
@@ -1568,13 +1568,13 @@ pg_get_function_identity_arguments(PG_FUNCTION_ARGS)
 	StringInfoData buf;
 	HeapTuple	proctup;
 
-	initStringInfo(&buf);
-
 	proctup = SearchSysCache(PROCOID,
 							 ObjectIdGetDatum(funcid),
 							 0, 0, 0);
 	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);
 
@@ -1598,17 +1598,17 @@ pg_get_function_result(PG_FUNCTION_ARGS)
 	Form_pg_proc procform;
 	int			ntabargs = 0;
 
-	initStringInfo(&buf);
-	initStringInfo(&argbuf);
-
 	proctup = SearchSysCache(PROCOID,
 							 ObjectIdGetDatum(funcid),
 							 0, 0, 0);
 
 	if (!HeapTupleIsValid(proctup))
-		elog(ERROR, "cache lookup failed for function %u", funcid);
+		PG_RETURN_NULL();
 	procform = (Form_pg_proc) GETSTRUCT(proctup);
 
+	initStringInfo(&buf);
+	initStringInfo(&argbuf);
+
 	ntabargs = print_function_arguments(&argbuf, proctup, true, true);
 
 	/* We have 3 cases: table function, setof function and others */

src/test/regress/expected/rules.out

@@ -1603,3 +1603,21 @@ 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)
+

src/test/regress/sql/rules.sql

@@ -941,3 +941,6 @@ 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);