planner: output a warning if plan rebuilding fails when reusing a cac…

…hed plan (#46278) (#46281)

close #46159

planner/core/plan_cache.go

@@ -353,7 +353,7 @@ func RebuildPlan4CachedPlan(p Plan) (ok bool) {
 	sc.InPreparedPlanBuilding = true
 	defer func() { sc.InPreparedPlanBuilding = false }()
 	if err := rebuildRange(p); err != nil {
-		// TODO: log or warn this error.
+		sc.AppendWarning(errors.Errorf("skip plan-cache: plan rebuild failed, %s", err.Error()))
 		return false // fail to rebuild ranges
 	}
 	if !sc.UseCache {

planner/core/plan_cache_test.go

@@ -2380,6 +2380,18 @@ func TestIssue45378(t *testing.T) {
 	tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("1"))
 }
 
+func TestIssue46159(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec(`create table t (a varchar(10), key(a(5)))`)
+	tk.MustExec(`prepare st from 'select a from t use index(a) where a=?'`)
+	tk.MustExec(`set @a='a'`)
+	tk.MustQuery(`execute st using @a`).Check(testkit.Rows())
+	tk.MustQuery(`execute st using @a`).Check(testkit.Rows())
+	tk.MustQuery(`show warnings`).Check(testkit.Rows("Warning 1105 skip plan-cache: plan rebuild failed, rebuild to get an unsafe range"))
+}
+
 func TestNonPreparedPlanCacheBuiltinFuncs(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)