4 files changed, 63 insertions, 3 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index bfc2ac17165..25fd051d6ef 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3067,6 +3067,7 @@ _copyObjectWithArgs(const ObjectWithArgs *from)
 
 	COPY_NODE_FIELD(objname);
 	COPY_NODE_FIELD(objargs);
+	COPY_SCALAR_FIELD(args_unspecified);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 54e9c983a0f..67529e3f861 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1119,6 +1119,7 @@ _equalObjectWithArgs(const ObjectWithArgs *a, const ObjectWithArgs *b)
 {
 	COMPARE_NODE_FIELD(objname);
 	COMPARE_NODE_FIELD(objargs);
+	COMPARE_SCALAR_FIELD(args_unspecified);
 
 	return true;
 }
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e7acc2d9a23..6316688a883 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -7202,6 +7202,33 @@ function_with_argtypes:
 					n->objargs = extractArgTypes($2);
 					$$ = n;
 				}
+			/*
+			 * Because of reduce/reduce conflicts, we can't use func_name
+			 * below, but we can write it out the long way, which actually
+			 * allows more cases.
+			 */
+			| type_func_name_keyword
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = list_make1(makeString(pstrdup($1)));
+					n->args_unspecified = true;
+					$$ = n;
+				}
+			| ColId
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = list_make1(makeString($1));
+					n->args_unspecified = true;
+					$$ = n;
+				}
+			| ColId indirection
+				{
+					ObjectWithArgs *n = makeNode(ObjectWithArgs);
+					n->objname = check_func_name(lcons(makeString($1), $2),
+												  yyscanner);
+					n->args_unspecified = true;
+					$$ = n;
+				}
 		;
 
 /*
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index dd9749f2056..55853c20bb4 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -1895,8 +1895,10 @@ func_signature_string(List *funcname, int nargs,
 
 /*
  * LookupFuncName
- *		Given a possibly-qualified function name and a set of argument types,
- *		look up the function.
+ *
+ * Given a possibly-qualified function name and optionally a set of argument
+ * types, look up the function.  Pass nargs == -1 to indicate that no argument
+ * types are specified.
  *
  * If the function name is not schema-qualified, it is sought in the current
  * namespace search path.
@@ -1914,6 +1916,35 @@ LookupFuncName(List *funcname, int nargs, const Oid *argtypes, bool noError)
 
 	clist = FuncnameGetCandidates(funcname, nargs, NIL, false, false, noError);
 
+	/*
+	 * If no arguments were specified, the name must yield a unique candidate.
+	 */
+	if (nargs == -1)
+	{
+		if (clist)
+		{
+			if (clist->next)
+			{
+				if (!noError)
+					ereport(ERROR,
+							(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
+							 errmsg("function name \"%s\" is not unique",
+									NameListToString(funcname)),
+							 errhint("Specify the argument list to select the function unambiguously.")));
+			}
+			else
+				return clist->oid;
+		}
+		else
+		{
+			if (!noError)
+				ereport(ERROR,
+						(errcode(ERRCODE_UNDEFINED_FUNCTION),
+						 errmsg("could not find a function named \"%s\"",
+								NameListToString(funcname))));
+		}
+	}
+
 	while (clist)
 	{
 		if (memcmp(argtypes, clist->args, nargs * sizeof(Oid)) == 0)
@@ -1962,7 +1993,7 @@ LookupFuncWithArgs(ObjectWithArgs *func, bool noError)
 		args_item = lnext(args_item);
 	}
 
-	return LookupFuncName(func->objname, argcount, argoids, noError);
+	return LookupFuncName(func->objname, func->args_unspecified ? -1 : argcount, argoids, noError);
 }
 
 /*