Add FunctionOidExtended function

src/backend/distributed/utils/function_utils.c

@@ -18,11 +18,27 @@
 #endif
 
 /*
- * FunctionOid looks for a function that has the given name and the given number
+ * FunctionOid searches for a function that has the given name and the given
- * of arguments, and returns the corresponding function's oid.
+ * number of arguments, and returns the corresponding function's oid. The
+ * function reports error if the target function is not found, or it found more
+ * matching instances.
  */
 Oid
 FunctionOid(const char *schemaName, const char *functionName, int argumentCount)
+{
+	return FunctionOidExtended(schemaName, functionName, argumentCount, false);
+}
+
+
+/*
+ * FunctionOidExtended searches for a given function identified by schema,
+ * functionName, and argumentCount. It reports error if the function is not
+ * found or there are more than one match. If the missingOK parameter is set
+ * and there are no matches, then the function returns InvalidOid.
+ */
+Oid
+FunctionOidExtended(const char *schemaName, const char *functionName, int argumentCount,
+					bool missingOK)
 {
 	FuncCandidateList functionList = NULL;
 	Oid functionOid = InvalidOid;
@@ -32,14 +48,18 @@ FunctionOid(const char *schemaName, const char *functionName, int argumentCount)
 	List *argumentList = NIL;
 	const bool findVariadics = false;
 	const bool findDefaults = false;
-	const bool missingOK = true;
 
 	functionList = FuncnameGetCandidates(qualifiedFunctionNameList, argumentCount,
 										 argumentList, findVariadics,
-										 findDefaults, missingOK);
+										 findDefaults, true);
 
 	if (functionList == NULL)
 	{
+		if (missingOK)
+		{
+			return InvalidOid;
+		}
+
 		ereport(ERROR, (errcode(ERRCODE_UNDEFINED_FUNCTION),
 						errmsg("function \"%s\" does not exist", functionName)));
 	}
@@ -51,6 +71,7 @@ FunctionOid(const char *schemaName, const char *functionName, int argumentCount)
 
 	/* get function oid from function list's head */
 	functionOid = functionList->oid;
+
 	return functionOid;
 }
 

src/include/distributed/function_utils.h

@@ -14,5 +14,7 @@
 /* Function declaration for getting oid for the given function name */
 extern Oid FunctionOid(const char *schemaName, const char *functionName,
 					   int argumentCount);
+extern Oid FunctionOidExtended(const char *schemaName, const char *functionName, int
+							   argumentCount, bool missingOK);
 extern ReturnSetInfo * FunctionCallGetTupleStore1(PGFunction function, Oid functionId,
 												  Datum argument);