From be112dc31d548db050aae1f6d0ebde1fd564e8e1 Mon Sep 17 00:00:00 2001
From: Yuanjia Zhang <zhangyuanjia@pingcap.com>
Date: Thu, 5 Jan 2023 11:20:20 +0800
Subject: [PATCH] planner: skip plan-cache for prepared queries with `INT in
 (Decimals...)` (#40312)

close pingcap/tidb#40224
---
 planner/core/expression_rewriter.go | 12 +++--------
 planner/core/plan_cache_test.go     | 32 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/planner/core/expression_rewriter.go b/planner/core/expression_rewriter.go
index 5a8f8a2df9f35..a2d1f242a0ff6 100644
--- a/planner/core/expression_rewriter.go
+++ b/planner/core/expression_rewriter.go
@@ -1559,16 +1559,10 @@ 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}) {
-					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.
-						er.sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: '%v' may be converted to INT", c.String()))
-						expression.RemoveMutableConst(er.sctx, []expression.Expression{c})
-					} else {
-						continue
+					if c.GetType().EvalType() == types.ETInt {
+						continue // no need to refine it
 					}
-				} else if !er.sctx.GetSessionVars().StmtCtx.UseCache {
-					// We should remove the mutable constant for correctness, because its value may be changed.
+					er.sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: '%v' may be converted to INT", c.String()))
 					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
index 0aa5c4e02d7cb..d7d47e55bc62e 100644
--- a/planner/core/plan_cache_test.go
+++ b/planner/core/plan_cache_test.go
@@ -385,6 +385,38 @@ func TestPlanCacheDiagInfo(t *testing.T) {
 	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)