planner: check nil pointer in rule_result_reorder to avoid panic (#48100

)

close #45044

pkg/planner/core/integration_test.go

@@ -2529,6 +2529,15 @@ func TestIssue46298(t *testing.T) {
 	tk.MustQuery("select *, first_value(v) over (partition by p order by o range between 3.1 preceding and 2.9 following) as a from test.first_range;")
 }
 
+func TestIssue45044(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`set tidb_enable_ordered_result_mode = on`)
+	tk.MustExec(`create table t1(c1 int)`)
+	tk.MustQuery(`select * from t1 group by t1.c1 having count(1) > 1 order by count(1) limit 10`).Check(testkit.Rows()) // no error
+}
+
 // https://github.com/pingcap/tidb/issues/41458
 func TestIssue41458(t *testing.T) {
 	store := testkit.CreateMockStore(t)

pkg/planner/core/rule_result_reorder.go

@@ -107,6 +107,9 @@ func (rs *resultReorder) extractHandleCol(lp LogicalPlan) *expression.Column {
 	switch x := lp.(type) {
 	case *LogicalSelection, *LogicalLimit:
 		handleCol := rs.extractHandleCol(lp.Children()[0])
+		if handleCol == nil {
+			return nil // fail to extract handle column from the child, just return nil.
+		}
 		if x.Schema().Contains(handleCol) {
 			// some Projection Operator might be inlined, so check the column again here
 			return handleCol