planner: update the plan cache strategy when expressions with parameters affect null-check

expression/expression.go

@@ -816,7 +816,7 @@ func SplitDNFItems(onExpr Expression) []Expression {
 // If the Expression is a non-constant value, it means the result is unknown.
 func EvaluateExprWithNull(ctx sessionctx.Context, schema *Schema, expr Expression) Expression {
 	if MaybeOverOptimized4PlanCache(ctx, []Expression{expr}) {
-		return expr
+		ctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.New("skip plan-cache: %v affects null check"))
 	}
 	if ctx.GetSessionVars().StmtCtx.InNullRejectCheck {
 		expr, _ = evaluateExprWithNullInNullRejectCheck(ctx, schema, expr)

expression/expression_test.go

@@ -75,8 +75,9 @@ func TestEvaluateExprWithNullAndParameters(t *testing.T) {
 	ltWithParam, err := newFunctionForTest(ctx, ast.LT, col0, param)
 	require.NoError(t, err)
 	res = EvaluateExprWithNull(ctx, schema, ltWithParam)
-	_, isScalarFunc := res.(*ScalarFunction)
-	require.True(t, isScalarFunc) // the expression with parameters is not evaluated
+	_, isConst := res.(*Constant)
+	require.True(t, isConst) // this expression is evaluated and skip-plan cache flag is set.
+	require.True(t, ctx.GetSessionVars().StmtCtx.SkipPlanCache)
 }
 
 func TestEvaluateExprWithNullNoChangeRetType(t *testing.T) {

planner/core/plan_cache_test.go

@@ -221,6 +221,88 @@ func TestIssue38533(t *testing.T) {
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 }
 
+func TestInvalidRange(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 where a>? and a<?'")
+	tk.MustExec("set @l=100, @r=10")
+	tk.MustExec("execute st using @l, @r")
+
+	tkProcess := tk.Session().ShowProcess()
+	ps := []*util.ProcessInfo{tkProcess}
+	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
+
+	tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).CheckAt([]int{0},
+		[][]interface{}{{"TableDual_5"}}) // use TableDual directly instead of TableFullScan
+
+	tk.MustExec("execute st using @l, @r")
+	tk.MustExec("execute st using @l, @r")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+}
+
+func TestIssue40093(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t1 (a int, b int)")
+	tk.MustExec("create table t2 (a int, b int, key(b, a))")
+	tk.MustExec("prepare st from 'select * from t1 left join t2 on t1.a=t2.a where t2.b in (?)'")
+	tk.MustExec("set @b=1")
+	tk.MustExec("execute st using @b")
+
+	tkProcess := tk.Session().ShowProcess()
+	ps := []*util.ProcessInfo{tkProcess}
+	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
+
+	tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).CheckAt([]int{0},
+		[][]interface{}{
+			{"Projection_9"},
+			{"└─HashJoin_21"},
+			{"  ├─IndexReader_26(Build)"},
+			{"  │ └─IndexRangeScan_25"}, // RangeScan instead of FullScan
+			{"  └─TableReader_24(Probe)"},
+			{"    └─Selection_23"},
+			{"      └─TableFullScan_22"},
+		})
+
+	tk.MustExec("execute st using @b")
+	tk.MustExec("execute st using @b")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+}
+
+func TestIssue38205(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE `item` (`id` int, `vid` varbinary(16), `sid` int)")
+	tk.MustExec("CREATE TABLE `lv` (`item_id` int, `sid` int, KEY (`sid`,`item_id`))")
+
+	tk.MustExec("prepare stmt from 'SELECT /*+ TIDB_INLJ(lv, item) */ * FROM lv LEFT JOIN item ON lv.sid = item.sid AND lv.item_id = item.id WHERE item.sid = ? AND item.vid IN (?, ?)'")
+	tk.MustExec("set @a=1, @b='1', @c='3'")
+	tk.MustExec("execute stmt using @a, @b, @c")
+
+	tkProcess := tk.Session().ShowProcess()
+	ps := []*util.ProcessInfo{tkProcess}
+	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
+
+	tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).CheckAt([]int{0},
+		[][]interface{}{
+			{"IndexJoin_10"},
+			{"├─TableReader_19(Build)"},
+			{"│ └─Selection_18"},
+			{"│   └─TableFullScan_17"}, // RangeScan instead of FullScan
+			{"└─IndexReader_9(Probe)"},
+			{"  └─Selection_8"},
+			{"    └─IndexRangeScan_7"},
+		})
+
+	tk.MustExec("execute stmt using @a, @b, @c")
+	tk.MustExec("execute stmt using @a, @b, @c")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+}
+
 func TestIgnoreInsertStmt(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)

util/ranger/detacher.go

@@ -581,9 +581,8 @@ func ExtractEqAndInCondition(sctx sessionctx.Context, conditions []expression.Ex
 		points[offset] = rb.intersection(points[offset], rb.build(cond, collator), collator)
 		if len(points[offset]) == 0 { // Early termination if false expression found
 			if expression.MaybeOverOptimized4PlanCache(sctx, conditions) {
-				// cannot return an empty-range for plan-cache since the range may become non-empty as parameters change
-				// for safety, return the whole conditions in this case
-				return nil, conditions, nil, nil, false
+				// `a>@x and a<@y` --> `invalid-range if @x>=@y`
+				sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
 			}
 			return nil, nil, nil, nil, true
 		}
@@ -606,9 +605,8 @@ func ExtractEqAndInCondition(sctx sessionctx.Context, conditions []expression.Ex
 			accesses[i] = nil
 		} else if len(points[i]) == 0 { // Early termination if false expression found
 			if expression.MaybeOverOptimized4PlanCache(sctx, conditions) {
-				// cannot return an empty-range for plan-cache since the range may become non-empty as parameters change
-				// for safety, return the whole conditions in this case
-				return nil, conditions, nil, nil, false
+				// `a>@x and a<@y` --> `invalid-range if @x>=@y`
+				sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
 			}
 			return nil, nil, nil, nil, true
 		} else {