executor: fix concurrent use of testkit in tests and add nil check (#…

…40627)

close #40206

executor/executor_test.go

@@ -5556,6 +5556,8 @@ func TestAdmin(t *testing.T) {
 	}))
 	tk := testkit.NewTestKit(t, store)
 	tk.MustExec("use test")
+	tk2 := testkit.NewTestKit(t, store)
+	tk2.MustExec("use test")
 	tk.MustExec("drop table if exists admin_test")
 	tk.MustExec("create table admin_test (c1 int, c2 int, c3 int default 1, index (c1))")
 	tk.MustExec("insert admin_test (c1) values (1),(2),(NULL)")
@@ -5680,7 +5682,7 @@ func TestAdmin(t *testing.T) {
 		// check that the result set has no duplication
 		defer wg.Done()
 		for i := 0; i < 10; i++ {
-			result := tk.MustQuery(`admin show ddl job queries 20`)
+			result := tk2.MustQuery(`admin show ddl job queries 20`)
 			rows := result.Rows()
 			rowIDs := make(map[string]struct{})
 			for _, row := range rows {
@@ -5711,7 +5713,7 @@ func TestAdmin(t *testing.T) {
 		// check that the result set has no duplication
 		defer wg2.Done()
 		for i := 0; i < 10; i++ {
-			result := tk.MustQuery(`admin show ddl job queries limit 3 offset 2`)
+			result := tk2.MustQuery(`admin show ddl job queries limit 3 offset 2`)
 			rows := result.Rows()
 			rowIDs := make(map[string]struct{})
 			for _, row := range rows {

planner/core/encode.go

@@ -262,6 +262,9 @@ type planDigester struct {
 
 // NormalizeFlatPlan normalizes a FlatPhysicalPlan and generates plan digest.
 func NormalizeFlatPlan(flat *FlatPhysicalPlan) (normalized string, digest *parser.Digest) {
+	if flat == nil {
+		return "", parser.NewDigest(nil)
+	}
 	selectPlan, selectPlanOffset := flat.Main.GetSelectPlan()
 	if len(selectPlan) == 0 || !selectPlan[0].IsPhysicalPlan {
 		return "", parser.NewDigest(nil)