Support GROUP BY () in PostgreSQL

Author: nene

src/parser.pegjs

@@ -801,6 +801,7 @@ group_by_distinct
 
 grouping_element
   = group_by_rollup
+  / paren$empty_list
   / expr
 
 group_by_rollup

test/select/group_by.test.ts

@@ -13,6 +13,12 @@ describe("select GROUP BY", () => {
   it("supports GROUP BY with list expression", () => {
     testClauseWc("GROUP BY (id, name), age");
   });
+  dialect("postgresql", () => {
+    it("supports GROUP BY empty list", () => {
+      testClauseWc("GROUP BY ()");
+      testClauseWc("GROUP BY foo, (), bar, ()");
+    });
+  });
 
   dialect(["bigquery", "postgresql"], () => {
     it("supports GROUP BY ROLLUP()", () => {