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

executor/explainfor_test.go

@@ -551,9 +551,9 @@ func TestIssue28259(t *testing.T) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	require.Len(t, res.Rows(), 4)
-	require.Regexp(t, ".*Selection.*", res.Rows()[0][0])
-	require.Regexp(t, ".*IndexFullScan.*", res.Rows()[3][0])
+	require.Len(t, res.Rows(), 3)
+	require.Regexp(t, ".*Selection.*", res.Rows()[1][0])
+	require.Regexp(t, ".*IndexFullScan.*", res.Rows()[2][0])
 
 	res = tk.MustQuery("explain format = 'brief' select col1 from UK_GCOL_VIRTUAL_18588 use index(UK_COL1) " +
 		"where col1 between -1696020282760139948 and -2619168038882941276 or col1 < -4004648990067362699;")
@@ -589,11 +589,9 @@ func TestIssue28259(t *testing.T) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	require.Len(t, res.Rows(), 5)
-	require.Regexp(t, ".*Selection.*", res.Rows()[1][0])
-	require.Equal(t, "lt(test.t.b, 1), or(and(ge(test.t.a, 2), le(test.t.a, 1)), lt(test.t.a, 1))", res.Rows()[1][4])
-	require.Regexp(t, ".*IndexReader.*", res.Rows()[2][0])
-	require.Regexp(t, ".*IndexRangeScan.*", res.Rows()[4][0])
+	require.Len(t, res.Rows(), 4)
+	require.Regexp(t, ".*Selection.*", res.Rows()[2][0])
+	require.Regexp(t, ".*IndexRangeScan.*", res.Rows()[3][0])
 
 	res = tk.MustQuery("explain format = 'brief' select a from t use index(idx) " +
 		"where (a between 0 and 2 or a < 2) and b < 1;")
@@ -636,12 +634,11 @@ func TestIssue28259(t *testing.T) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	require.Len(t, res.Rows(), 6)
-	require.Regexp(t, ".*Selection.*", res.Rows()[1][0])
-	require.Regexp(t, ".*IndexLookUp.*", res.Rows()[2][0])
-	require.Regexp(t, ".*IndexRangeScan.*", res.Rows()[3][0])
-	require.Regexp(t, ".*Selection.*", res.Rows()[4][0])
-	require.Regexp(t, ".*TableRowIDScan.*", res.Rows()[5][0])
+	require.Len(t, res.Rows(), 5)
+	require.Regexp(t, ".*IndexLookUp.*", res.Rows()[1][0])
+	require.Regexp(t, ".*IndexRangeScan.*", res.Rows()[2][0])
+	require.Regexp(t, ".*Selection.*", res.Rows()[3][0])
+	require.Regexp(t, ".*TableRowIDScan.*", res.Rows()[4][0])
 
 	res = tk.MustQuery("explain format = 'brief' select /*+ USE_INDEX(t, idx) */ a from t use index(idx) " +
 		"where (a between 0 and 2 or a < 2) and b < 1;")
@@ -860,7 +857,7 @@ func TestIndexMerge4PlanCache(t *testing.T) {
 	tk.MustExec("prepare stmt from 'select /*+ use_index_merge(t1) */ * from t1 where c=? or (b=? and (a >= ? and a <= ?));';")
 	tk.MustQuery("execute stmt using @a, @a, @b, @a").Check(testkit.Rows("10 10 10"))
 	tk.MustQuery("execute stmt using @b, @b, @b, @b").Check(testkit.Rows("11 11 11"))
-	tk.MustQuery("select @@last_plan_from_cache;").Check(testkit.Rows("1"))
+	tk.MustQuery("select @@last_plan_from_cache;").Check(testkit.Rows("0"))
 
 	tk.MustExec("prepare stmt from 'select /*+ use_index_merge(t1) */ * from t1 where c=10 or (a >=? and a <= ?);';")
 	tk.MustExec("set @a=9, @b=10, @c=11;")

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)

planner/core/prepare_test.go

@@ -1939,7 +1939,7 @@ func TestPlanCachePointGetAndTableDual(t *testing.T) {
 	tk.MustQuery("execute s0 using @a0, @b0, @a0").Check(testkit.Rows())
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 	tk.MustQuery("execute s0 using @a0, @a0, @b0").Check(testkit.Rows("0000 7777 1"))
-	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 
 	tk.MustExec("create table t1(c1 varchar(20), c2 varchar(20), c3 bigint(20), primary key(c1, c2))")
 	tk.MustExec("insert into t1 values('0000','7777',1)")

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 {