mocktikv: avoid sorting multiple times with unstable order (pingcap#1…

…5898) (pingcap#16198)
crazycs520 · Apr 9, 2020 · c21ca8f · c21ca8f
1 parent 4c0624c
commit c21ca8f
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/executor/executor_test.go b/executor/executor_test.go
@@ -3990,3 +3990,15 @@ func testGetTableByName(c *C, ctx sessionctx.Context, db, table string) table.Ta
 	c.Assert(err, IsNil)
 	return tbl
 }
+
+func (s *testSuite1) TestIssue15767(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test;")
+	tk.MustExec("drop table if exists tt;")
+	tk.MustExec("create table t(a int, b char);")
+	tk.MustExec("insert into t values (1,'s'),(2,'b'),(1,'c'),(2,'e'),(1,'a');")
+	tk.MustExec("insert into t select * from t;")
+	tk.MustExec("insert into t select * from t;")
+	tk.MustExec("insert into t select * from t;")
+	tk.MustQuery("select b, count(*) from ( select b from t order by a limit 20 offset 2) as s group by b order by b;").Check(testkit.Rows("a 6", "c 7", "s 7"))
+}
diff --git a/store/mockstore/mocktikv/executor.go b/store/mockstore/mocktikv/executor.go
@@ -533,6 +533,7 @@ func (e *topNExec) Next(ctx context.Context) (value [][]byte, err error) {
 				return nil, errors.Trace(err)
 			}
 			if !hasMore {
+				sort.Sort(&e.heap.topNSorter)
 				break
 			}
 		}
@@ -541,7 +542,6 @@ func (e *topNExec) Next(ctx context.Context) (value [][]byte, err error) {
 	if e.cursor >= len(e.heap.rows) {
 		return nil, nil
 	}
-	sort.Sort(&e.heap.topNSorter)
 	row := e.heap.rows[e.cursor]
 	e.cursor++