diff --git a/planner/core/expression_rewriter.go b/planner/core/expression_rewriter.go
index a698a2edfd685..0cdbdb078203c 100644
--- a/planner/core/expression_rewriter.go
+++ b/planner/core/expression_rewriter.go
@@ -1485,6 +1485,7 @@ func (er *expressionRewriter) inToExpression(lLen int, not bool, tp *types.Field
 			if c, ok := args[i].(*expression.Constant); ok {
 				var isExceptional bool
 				if expression.MaybeOverOptimized4PlanCache(er.sctx, []expression.Expression{c}) {
+<<<<<<< HEAD
 					if c.GetType().EvalType() == types.ETString {
 						// 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.
@@ -1495,6 +1496,12 @@ func (er *expressionRewriter) inToExpression(lLen int, not bool, tp *types.Field
 					}
 				} else if er.sctx.GetSessionVars().StmtCtx.SkipPlanCache {
 					// We should remove the mutable constant for correctness, because its value may be changed.
+=======
+					if c.GetType().EvalType() == types.ETInt {
+						continue // no need to refine it
+					}
+					er.sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: '%v' may be converted to INT", c.String()))
+>>>>>>> be112dc31d (planner: skip plan-cache for prepared queries with `INT in (Decimals...)` (#40312))
 					expression.RemoveMutableConst(er.sctx, []expression.Expression{c})
 				}
 				args[i], isExceptional = expression.RefineComparedConstant(er.sctx, *leftFt, c, opcode.EQ)
diff --git a/planner/core/plan_cache_test.go b/planner/core/plan_cache_test.go
new file mode 100644
index 0000000000000..d7d47e55bc62e
--- /dev/null
+++ b/planner/core/plan_cache_test.go
@@ -0,0 +1,460 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package core_test
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math/rand"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/pingcap/tidb/expression"
+	"github.com/pingcap/tidb/parser/mysql"
+	plannercore "github.com/pingcap/tidb/planner/core"
+	"github.com/pingcap/tidb/testkit"
+	"github.com/pingcap/tidb/types"
+	"github.com/pingcap/tidb/util"
+	"github.com/stretchr/testify/require"
+)
+
+type mockParameterizer struct {
+	action string
+}
+
+func (mp *mockParameterizer) Parameterize(originSQL string) (paramSQL string, params []expression.Expression, ok bool, err error) {
+	switch mp.action {
+	case "error":
+		return "", nil, false, errors.New("error")
+	case "not_support":
+		return "", nil, false, nil
+	}
+	// only support SQL like 'select * from t where col {op} {int} and ...'
+	prefix := "select * from t where "
+	if !strings.HasPrefix(originSQL, prefix) {
+		return "", nil, false, nil
+	}
+	buf := make([]byte, 0, 32)
+	buf = append(buf, prefix...)
+	for i, condStr := range strings.Split(originSQL[len(prefix):], "and") {
+		if i > 0 {
+			buf = append(buf, " and "...)
+		}
+		tmp := strings.Split(strings.TrimSpace(condStr), " ")
+		if len(tmp) != 3 { // col {op} {val}
+			return "", nil, false, nil
+		}
+		buf = append(buf, tmp[0]...)
+		buf = append(buf, tmp[1]...)
+		buf = append(buf, '?')
+
+		intParam, err := strconv.Atoi(tmp[2])
+		if err != nil {
+			return "", nil, false, nil
+		}
+		params = append(params, &expression.Constant{Value: types.NewDatum(intParam), RetType: types.NewFieldType(mysql.TypeLong)})
+	}
+	return string(buf), params, true, nil
+}
+
+func TestInitLRUWithSystemVar(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("set @@session.tidb_prepared_plan_cache_size = 0") // MinValue: 1
+	tk.MustQuery("select @@session.tidb_prepared_plan_cache_size").Check(testkit.Rows("1"))
+	sessionVar := tk.Session().GetSessionVars()
+
+	lru := plannercore.NewLRUPlanCache(uint(sessionVar.PreparedPlanCacheSize), 0, 0, plannercore.PickPlanFromBucket, tk.Session())
+	require.NotNil(t, lru)
+}
+
+func TestNonPreparedPlanCacheWithExplain(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec("create table t(a int)")
+	tk.MustExec("set tidb_enable_non_prepared_plan_cache=1")
+	tk.MustExec("select * from t where a=1") // cache this plan
+
+	tk.MustQuery("explain select * from t where a=2").Check(testkit.Rows(
+		`Selection_8 10.00 root  eq(test.t.a, 2)`,
+		`└─TableReader_7 10.00 root  data:Selection_6`,
+		`  └─Selection_6 10.00 cop[tikv]  eq(test.t.a, 2)`,
+		`    └─TableFullScan_5 10000.00 cop[tikv] table:t keep order:false, stats:pseudo`))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+
+	tk.MustQuery("explain format=verbose select * from t where a=2").Check(testkit.Rows(
+		`Selection_8 10.00 169474.57 root  eq(test.t.a, 2)`,
+		`└─TableReader_7 10.00 168975.57 root  data:Selection_6`,
+		`  └─Selection_6 10.00 2534000.00 cop[tikv]  eq(test.t.a, 2)`,
+		`    └─TableFullScan_5 10000.00 2035000.00 cop[tikv] table:t keep order:false, stats:pseudo`))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+
+	tk.MustQuery("explain analyze select * from t where a=2").CheckAt([]int{0, 1, 2, 3}, [][]interface{}{
+		{"Selection_8", "10.00", "0", "root"},
+		{"└─TableReader_7", "10.00", "0", "root"},
+		{"  └─Selection_6", "10.00", "0", "cop[tikv]"},
+		{"    └─TableFullScan_5", "10000.00", "0", "cop[tikv]"},
+	})
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+}
+
+func TestNonPreparedPlanCacheFallback(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`create table t (a int)`)
+	for i := 0; i < 5; i++ {
+		tk.MustExec(fmt.Sprintf("insert into t values (%v)", i))
+	}
+	tk.MustExec("set tidb_enable_non_prepared_plan_cache=1")
+
+	// inject a fault to GeneratePlanCacheStmtWithAST
+	ctx := context.WithValue(context.Background(), "____GeneratePlanCacheStmtWithASTErr", struct{}{})
+	tk.MustQueryWithContext(ctx, "select * from t where a in (1, 2)").Sort().Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // cannot generate PlanCacheStmt
+	tk.MustQueryWithContext(ctx, "select * from t where a in (1, 3)").Sort().Check(testkit.Rows("1", "3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // cannot generate PlanCacheStmt
+	tk.MustQuery("select * from t where a in (1, 2)").Sort().Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select * from t where a in (1, 3)").Sort().Check(testkit.Rows("1", "3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // no error
+
+	// inject a fault to GetPlanFromSessionPlanCache
+	tk.MustQuery("select * from t where a=1").Check(testkit.Rows("1")) // cache this plan
+	tk.MustQuery("select * from t where a=2").Check(testkit.Rows("2")) // plan from cache
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	ctx = context.WithValue(context.Background(), "____GetPlanFromSessionPlanCacheErr", struct{}{})
+	tk.MustQueryWithContext(ctx, "select * from t where a=3").Check(testkit.Rows("3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // fallback to the normal opt-path
+	tk.MustQueryWithContext(ctx, "select * from t where a=4").Check(testkit.Rows("4"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // fallback to the normal opt-path
+	tk.MustQueryWithContext(context.Background(), "select * from t where a=0").Check(testkit.Rows("0"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // use the cached plan if no error
+
+	// inject a fault to RestoreASTWithParams
+	ctx = context.WithValue(context.Background(), "____GetPlanFromSessionPlanCacheErr", struct{}{})
+	ctx = context.WithValue(ctx, "____RestoreASTWithParamsErr", struct{}{})
+	_, err := tk.ExecWithContext(ctx, "select * from t where a=1")
+	require.NotNil(t, err)
+}
+
+func TestNonPreparedPlanCacheBasically(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`create table t (a int, b int, c int, d int, primary key(a), key(b), key(c, d))`)
+	for i := 0; i < 20; i++ {
+		tk.MustExec(fmt.Sprintf("insert into t values (%v, %v, %v, %v)", i, rand.Intn(20), rand.Intn(20), rand.Intn(20)))
+	}
+
+	queries := []string{
+		"select * from t where a<10",
+		"select * from t where a<13 and b<15",
+		"select * from t where b=13",
+		"select * from t where c<8",
+		"select * from t where d>8",
+		"select * from t where c=8 and d>10",
+		"select * from t where a<12 and b<13 and c<12 and d>2",
+	}
+
+	for _, query := range queries {
+		tk.MustExec(`set tidb_enable_non_prepared_plan_cache=0`)
+		resultNormal := tk.MustQuery(query).Sort()
+		tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("0"))
+
+		tk.MustExec(`set tidb_enable_non_prepared_plan_cache=1`)
+		tk.MustQuery(query)                                                    // first process
+		tk.MustQuery(query).Sort().Check(resultNormal.Rows())                  // equal to the result without plan-cache
+		tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("1")) // this plan is from plan-cache
+	}
+}
+
+func TestIssue38269(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`set @@tidb_enable_prepared_plan_cache=1`)
+	tk.MustExec("set @@tidb_enable_collect_execution_info=0")
+	tk.MustExec("use test")
+	tk.MustExec("create table t1(a int)")
+	tk.MustExec("create table t2(a int, b int, c int, index idx(a, b))")
+	tk.MustExec("prepare stmt1 from 'select /*+ inl_join(t2) */ * from t1 join t2 on t1.a = t2.a where t2.b in (?, ?, ?)'")
+	tk.MustExec("set @a = 10, @b = 20, @c = 30, @d = 40, @e = 50, @f = 60")
+	tk.MustExec("execute stmt1 using @a, @b, @c")
+	tk.MustExec("execute stmt1 using @d, @e, @f")
+	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.Contains(t, rows[6][4], "range: decided by [eq(test.t2.a, test.t1.a) in(test.t2.b, 40, 50, 60)]")
+}
+
+func TestIssue38533(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 /*+ use_index(t, a) */ a from t where a=? and a=?"`)
+	tk.MustExec(`set @a=1`)
+	tk.MustExec(`execute st using @a, @a`)
+	tkProcess := tk.Session().ShowProcess()
+	ps := []*util.ProcessInfo{tkProcess}
+	tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
+	plan := tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Rows()
+	require.True(t, strings.Contains(plan[1][0].(string), "RangeScan")) // range-scan instead of full-scan
+
+	tk.MustExec(`execute st using @a, @a`)
+	tk.MustExec(`execute st using @a, @a`)
+	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)
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a int)")
+
+	// do not cache native insert-stmt
+	tk.MustExec("prepare st from 'insert into t values (1)'")
+	tk.MustExec("execute st")
+	tk.MustExec("execute st")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	// ignore-hint in insert-stmt can work
+	tk.MustExec("prepare st from 'insert into t select * from t'")
+	tk.MustExec("execute st")
+	tk.MustExec("execute st")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	tk.MustExec("prepare st from 'insert /*+ ignore_plan_cache() */ into t select * from t'")
+	tk.MustExec("execute st")
+	tk.MustExec("execute st")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+}
+
+func TestIssue38710(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists UK_NO_PRECISION_19392;")
+	tk.MustExec("CREATE TABLE `UK_NO_PRECISION_19392` (\n  `COL1` bit(1) DEFAULT NULL,\n  `COL2` varchar(20) COLLATE utf8mb4_bin DEFAULT NULL,\n  `COL4` datetime DEFAULT NULL,\n  `COL3` bigint DEFAULT NULL,\n  `COL5` float DEFAULT NULL,\n  UNIQUE KEY `UK_COL1` (`COL1`)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;")
+	tk.MustExec("INSERT INTO `UK_NO_PRECISION_19392` VALUES (0x00,'缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈','9294-12-26 06:50:40',-3088380202191555887,-3.33294e38),(NULL,'仲膩蕦圓猴洠飌镂喵疎偌嫺荂踖Ƕ藨蜿諪軁笞','1746-08-30 18:04:04',-4016793239832666288,-2.52633e38),(0x01,'冑溜畁脊乤纊繳蟥哅稐奺躁悼貘飗昹槐速玃沮','1272-01-19 23:03:27',-8014797887128775012,1.48868e38);\n")
+	tk.MustExec(`prepare stmt from 'select * from UK_NO_PRECISION_19392 where col1 between ? and ? or col3 = ? or col2 in (?, ?, ?);';`)
+	tk.MustExec("set @a=0x01, @b=0x01, @c=-3088380202191555887, @d=\"缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈\", @e=\"缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈\", @f=\"缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈\";")
+	rows := tk.MustQuery(`execute stmt using @a,@b,@c,@d,@e,@f;`) // can not be cached because @a = @b
+	require.Equal(t, 2, len(rows.Rows()))
+
+	tk.MustExec(`set @a=NULL, @b=NULL, @c=-4016793239832666288, @d="缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈", @e="仲膩蕦圓猴洠飌镂喵疎偌嫺荂踖Ƕ藨蜿諪軁笞", @f="缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈";`)
+	rows = tk.MustQuery(`execute stmt using @a,@b,@c,@d,@e,@f;`)
+	require.Equal(t, 2, len(rows.Rows()))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	rows = tk.MustQuery(`execute stmt using @a,@b,@c,@d,@e,@f;`)
+	require.Equal(t, 2, len(rows.Rows()))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+
+	tk.MustExec(`set @a=0x01, @b=0x01, @c=-3088380202191555887, @d="缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈", @e="缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈", @f="缎馗惫砲兣肬憵急鳸嫅稩邏蠧鄂艘腯灩專妴粈";`)
+	rows = tk.MustQuery(`execute stmt using @a,@b,@c,@d,@e,@f;`)
+	require.Equal(t, 2, len(rows.Rows()))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // can not use the cache because the types for @a and @b are not equal to the cached plan
+}
+
+func TestPlanCacheDiagInfo(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a int, b int, key(a), key(b))")
+
+	tk.MustExec("prepare stmt from 'select * from t where a in (select a from t)'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has sub-queries is un-cacheable"))
+
+	tk.MustExec("prepare stmt from 'select /*+ ignore_plan_cache() */ * from t'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: ignore plan cache by hint"))
+
+	tk.MustExec("prepare stmt from 'select * from t limit ?'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has 'limit ?' is un-cacheable"))
+
+	tk.MustExec("prepare stmt from 'select * from t limit ?, 1'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has 'limit ?, 10' is un-cacheable"))
+
+	tk.MustExec("prepare stmt from 'select * from t order by ?'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has 'order by ?' is un-cacheable"))
+
+	tk.MustExec("prepare stmt from 'select * from t where a=?'")
+	tk.MustExec("set @a='123'")
+	tk.MustExec("execute stmt using @a") // '123' -> 123
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: '123' may be converted to INT"))
+
+	tk.MustExec("prepare stmt from 'select * from t where a=? and a=?'")
+	tk.MustExec("set @a=1, @b=1")
+	tk.MustExec("execute stmt using @a, @b") // a=1 and a=1 -> a=1
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: some parameters may be overwritten"))
+}
+
+func TestIssue40224(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 a from t where a in (?, ?)'")
+	tk.MustExec("set @a=1.0, @b=2.0")
+	tk.MustExec("execute st using @a, @b")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: '1.0' may be converted to INT"))
+	tk.MustExec("execute st using @a, @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{}{
+			{"IndexReader_6"},
+			{"└─IndexRangeScan_5"}, // range scan not full scan
+		})
+
+	tk.MustExec("set @a=1, @b=2")
+	tk.MustExec("execute st using @a, @b")
+	tk.MustQuery("show warnings").Check(testkit.Rows()) // no warning for INT values
+	tk.MustExec("execute st using @a, @b")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // cacheable for INT
+	tk.MustExec("execute st using @a, @b")
+	tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).CheckAt([]int{0},
+		[][]interface{}{
+			{"IndexReader_6"},
+			{"└─IndexRangeScan_5"}, // range scan not full scan
+		})
+}
+
+func TestIssue40225(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<?'")
+	tk.MustExec("set @a='1'")
+	tk.MustExec("execute st using @a")
+	tk.MustQuery("show warnings").Sort().Check(testkit.Rows("Warning 1105 skip plan-cache: '1' may be converted to INT")) // plan-cache limitation
+	tk.MustExec("create binding for select * from t where a<1 using select /*+ ignore_plan_cache() */ * from t where a<1")
+	tk.MustExec("execute st using @a")
+	tk.MustQuery("show warnings").Sort().Check(testkit.Rows("Warning 1105 skip plan-cache: ignore plan cache by binding"))
+	// no warning about plan-cache limitations('1' -> INT) since plan-cache is totally disabled.
+
+	tk.MustExec("prepare st from 'select * from t where a>?'")
+	tk.MustExec("set @a=1")
+	tk.MustExec("execute st using @a")
+	tk.MustExec("execute st using @a")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	tk.MustExec("create binding for select * from t where a>1 using select /*+ ignore_plan_cache() */ * from t where a>1")
+	tk.MustExec("execute st using @a")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	tk.MustExec("execute st using @a")
+	tk.MustQuery("select @@last_plan_from_binding").Check(testkit.Rows("1"))
+}
+
+func TestUncacheableReason(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a int)")
+
+	tk.MustExec("prepare st from 'select * from t limit ?'")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has 'limit ?' is un-cacheable"))
+
+	tk.MustExec("set @a=1")
+	tk.MustQuery("execute st using @a").Check(testkit.Rows())
+	tk.MustExec("prepare st from 'select * from t limit ?'")
+	// show the corresponding un-cacheable reason at execute-stage as well
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip plan-cache: query has 'limit ?' is un-cacheable"))
+}