executor: fix incorrect results when there is an IndexLookUp under th…

…e inner side of an Apply (pingcap#19496) (pingcap#19508)

* cherry pick pingcap#19496 to release-4.0

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

* fix CI

Co-authored-by: Yuanjia Zhang <zhangyuanjia@pingcap.com>

executor/distsql.go

@@ -557,6 +557,7 @@ func (e *IndexLookUpExecutor) Close() error {
 	e.finished = nil
 	e.workerStarted = false
 	e.memTracker = nil
+	e.resultCurr = nil
 	return nil
 }
 

executor/executor_test.go

@@ -5940,3 +5940,14 @@ func (s *testSplitTable) TestKillTableReader(c *C) {
 	atomic.StoreUint32(&tk.Se.GetSessionVars().Killed, 1)
 	wg.Wait()
 }
+
+func (s *testSuite) TestIssue19372(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test;")
+	tk.MustExec("drop table if exists t1, t2;")
+	tk.MustExec("create table t1 (c_int int, c_str varchar(40), key(c_str));")
+	tk.MustExec("create table t2 like t1;")
+	tk.MustExec("insert into t1 values (1, 'a'), (2, 'b'), (3, 'c');")
+	tk.MustExec("insert into t2 select * from t1;")
+	tk.MustQuery("select (select t2.c_str from t2 where t2.c_str <= t1.c_str and t2.c_int in (1, 2) order by t2.c_str limit 1) x from t1 order by c_int;").Check(testkit.Rows("a", "a", "a"))
+}