planner: label plans as over-optimized for plan cache after refining cmp-function arguments

expression/builtin_compare.go

@@ -1565,31 +1565,23 @@ func (c *compareFunctionClass) refineArgs(ctx sessionctx.Context, args []Express
 	arg0Type, arg1Type := args[0].GetType(), args[1].GetType()
 	arg0IsInt := arg0Type.EvalType() == types.ETInt
 	arg1IsInt := arg1Type.EvalType() == types.ETInt
-	arg0IsString := arg0Type.EvalType() == types.ETString
-	arg1IsString := arg1Type.EvalType() == types.ETString
 	arg0, arg0IsCon := args[0].(*Constant)
 	arg1, arg1IsCon := args[1].(*Constant)
 	isExceptional, finalArg0, finalArg1 := false, args[0], args[1]
 	isPositiveInfinite, isNegativeInfinite := false, false
+	signedFlag0, signedFlag1 := mysql.HasUnsignedFlag(args[0].GetType().GetFlag()), mysql.HasUnsignedFlag(args[1].GetType().GetFlag())
+
+	// handle over-optimization for plan cache
 	if MaybeOverOptimized4PlanCache(ctx, args) {
-		// To keep the result be compatible with MySQL, refine `int non-constant <cmp> str constant`
-		// here and skip this refine operation in all other cases for safety.
-		if (arg0IsInt && !arg0IsCon && arg1IsString && arg1IsCon) || (arg1IsInt && !arg1IsCon && arg0IsString && arg0IsCon) {
-			var reason error
-			if arg1IsString {
-				reason = errors.Errorf("skip plan-cache: '%v' may be converted to INT", arg1.String())
-			} else { // arg0IsString
-				reason = errors.Errorf("skip plan-cache: '%v' may be converted to INT", arg0.String())
-			}
-			ctx.GetSessionVars().StmtCtx.SetSkipPlanCache(reason)
-			RemoveMutableConst(ctx, args)
-		} else {
-			return args
+		if arg0IsInt && arg1IsInt && signedFlag0 == signedFlag1 {
+			return args // no need to refine them
 		}
-	} else if !ctx.GetSessionVars().StmtCtx.UseCache {
-		// We should remove the mutable constant for correctness, because its value may be changed.
-		RemoveMutableConst(ctx, args)
+		// label this plan as over-optimized if refine some args for safety.
+		reason := errors.Errorf("skip plan-cache: %v or %v may be rewritten", args[0].String(), args[1].String())
+		ctx.GetSessionVars().StmtCtx.SetSkipPlanCache(reason)
+		RemoveMutableConst(ctx, args) // skip plan cache and just remove all parameters
 	}
+
 	// int non-constant [cmp] non-int constant
 	if arg0IsInt && !arg0IsCon && !arg1IsInt && arg1IsCon {
 		arg1, isExceptional = RefineComparedConstant(ctx, *arg0Type, arg1, c.op)

planner/core/plan_cache_test.go

@@ -82,6 +82,46 @@ func TestInitLRUWithSystemVar(t *testing.T) {
 	require.NotNil(t, lru)
 }
 
+func TestIssue40679(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a int, key(a));")
+	tk.MustExec("prepare st from 'select * from t use index(a) where a < ?'")
+	tk.MustExec("set @a1=1.1")
+	tk.MustExec("execute st using @a1")
+
+	tkProcess := tk.Session().ShowProcess()
+	ps := []*util.ProcessInfo{tkProcess}
+	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
+	rows := tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Rows()
+	require.True(t, strings.Contains(rows[1][0].(string), "RangeScan")) // RangeScan not FullScan
+
+	tk.MustExec("execute st using @a1")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: test.t.a or 1.1 may be rewritten"))
+}
+
+func TestIssue41032(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec(`CREATE TABLE PK_SIGNED_10087 (
+	 COL1 mediumint(8) unsigned NOT NULL,
+	 COL2 varchar(20) DEFAULT NULL,
+	 COL4 datetime DEFAULT NULL,
+	 COL3 bigint(20) DEFAULT NULL,
+	 COL5 float DEFAULT NULL,
+	 PRIMARY KEY (COL1) )`)
+	tk.MustExec(`insert into PK_SIGNED_10087 values(0, "痥腜蟿鮤枓欜喧檕澙姭袐裄钭僇剕焍哓閲疁櫘", "0017-11-14 05:40:55", -4504684261333179273, 7.97449e37)`)
+	tk.MustExec(`prepare stmt from 'SELECT/*+ HASH_JOIN(t1, t2) */ t2.* FROM PK_SIGNED_10087 t1 JOIN PK_SIGNED_10087 t2 ON t1.col1 = t2.col1 WHERE t2.col1 >= ? AND t1.col1 >= ?;'`)
+	tk.MustExec(`set @a=0, @b=0`)
+	tk.MustQuery(`execute stmt using @a,@b`).Check(testkit.Rows("0 痥腜蟿鮤枓欜喧檕澙姭袐裄钭僇剕焍哓閲疁櫘 0017-11-14 05:40:55 -4504684261333179273 79744900000000000000000000000000000000"))
+	tk.MustQuery(`show warnings`).Check(testkit.Rows("Warning 1105 skip plan-cache: test.pk_signed_10087.col1 or 0 may be rewritten"))
+	tk.MustExec(`set @a=8950167, @b=16305982`)
+	tk.MustQuery(`execute stmt using @a,@b`).Check(testkit.Rows())
+	tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("0"))
+}
+
 func TestIssue40296(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)