planner: update the plan cache strategy when expressions with paramet…

…ers affect null-check (#40218) (#42637)

close #38205

executor/explainfor_test.go

@@ -623,9 +623,9 @@ func (s *testPrepareSerialSuite) TestIssue28259(c *C) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Se.SetSessionManager(&mockSessionManager1{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	c.Assert(len(res.Rows()), Equals, 4)
-	c.Assert(res.Rows()[0][0], Matches, ".*Selection.*")
-	c.Assert(res.Rows()[3][0], Matches, ".*IndexFullScan.*")
+	c.Assert(len(res.Rows()), Equals, 3)
+	c.Assert(res.Rows()[1][0], Matches, ".*Selection.*")
+	c.Assert(res.Rows()[2][0], Matches, ".*IndexFullScan.*")
 
 	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;")
@@ -661,11 +661,9 @@ func (s *testPrepareSerialSuite) TestIssue28259(c *C) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Se.SetSessionManager(&mockSessionManager1{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	c.Assert(len(res.Rows()), Equals, 5)
-	c.Assert(res.Rows()[1][0], Matches, ".*Selection.*")
-	c.Assert(res.Rows()[1][4], Equals, "lt(test.t.b, 1), or(and(ge(test.t.a, 2), le(test.t.a, 1)), lt(test.t.a, 1))")
-	c.Assert(res.Rows()[2][0], Matches, ".*IndexReader.*")
-	c.Assert(res.Rows()[4][0], Matches, ".*IndexRangeScan.*")
+	c.Assert(len(res.Rows()), Equals, 4)
+	c.Assert(res.Rows()[2][0], Matches, ".*Selection.*")
+	c.Assert(res.Rows()[3][0], Matches, ".*IndexRangeScan.*")
 
 	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;")
@@ -708,12 +706,11 @@ func (s *testPrepareSerialSuite) TestIssue28259(c *C) {
 	ps = []*util.ProcessInfo{tkProcess}
 	tk.Se.SetSessionManager(&mockSessionManager1{PS: ps})
 	res = tk.MustQuery("explain for connection " + strconv.FormatUint(tkProcess.ID, 10))
-	c.Assert(len(res.Rows()), Equals, 6)
-	c.Assert(res.Rows()[1][0], Matches, ".*Selection.*")
-	c.Assert(res.Rows()[2][0], Matches, ".*IndexLookUp.*")
-	c.Assert(res.Rows()[3][0], Matches, ".*IndexRangeScan.*")
-	c.Assert(res.Rows()[4][0], Matches, ".*Selection.*")
-	c.Assert(res.Rows()[5][0], Matches, ".*TableRowIDScan.*")
+	c.Assert(len(res.Rows()), Equals, 5)
+	c.Assert(res.Rows()[1][0], Matches, ".*IndexLookUp.*")
+	c.Assert(res.Rows()[2][0], Matches, ".*IndexRangeScan.*")
+	c.Assert(res.Rows()[3][0], Matches, ".*Selection.*")
+	c.Assert(res.Rows()[4][0], Matches, ".*TableRowIDScan.*")
 
 	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;")
@@ -952,7 +949,7 @@ func (s *testPrepareSerialSuite) TestIndexMerge4PlanCache(c *C) {
 	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;")
@@ -974,7 +971,7 @@ func (s *testPrepareSerialSuite) TestIndexMerge4PlanCache(c *C) {
 	tk.MustExec("set @a=9, @b=10, @c=11;")
 	tk.MustQuery("execute stmt using @c, @a;").Check(testkit.Rows("10 10 10"))
 	tk.MustQuery("execute stmt using @a, @c;").Check(testkit.Rows("10 10 10", "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.MustQuery("execute stmt using @a, @a;").Check(testkit.Rows("10 10 10"))
 	tk.MustQuery("select @@last_plan_from_cache;").Check(testkit.Rows("1"))
 

expression/expression.go

@@ -794,7 +794,7 @@ 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.SkipPlanCache = true
 	}
 	return evaluateExprWithNull(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 TestConstant(t *testing.T) {

planner/core/prepare_test.go

@@ -2058,7 +2058,7 @@ func (s *testPlanSerialSuite) TestPlanCachePointGetAndTableDual(c *C) {
 	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)")
@@ -2096,7 +2096,7 @@ func (s *testPlanSerialSuite) TestPlanCachePointGetAndTableDual(c *C) {
 	tk.MustQuery("execute s3 using @b3,@a3").Check(testkit.Rows())
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 	tk.MustQuery("execute s3 using @a3,@b3").Check(testkit.Rows("2 1 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 t4(c1 int primary key, c2 int, c3 int, key(c2))")
 	tk.MustExec("insert into t4 values(2,1,1)")
@@ -2112,7 +2112,7 @@ func (s *testPlanSerialSuite) TestPlanCachePointGetAndTableDual(c *C) {
 	tk.MustQuery("execute s4 using @b4,@a4").Check(testkit.Rows())
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 	tk.MustQuery("execute s4 using @a4,@b4").Check(testkit.Rows("2 1 1"))
-	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
 }
 
 func (s *testPrepareSuite) TestIssue26873(c *C) {

util/ranger/detacher.go

@@ -537,9 +537,8 @@ 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.SkipPlanCache = true
 			}
 			return nil, nil, nil, nil, true
 		}
@@ -562,9 +561,8 @@ 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.SkipPlanCache = true
 			}
 			return nil, nil, nil, nil, true
 		} else {