From efa487eddc1fd3dafca86a310200fe5d317332c0 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Thu, 14 Jan 2021 15:50:35 +0800
Subject: [PATCH] expression: fix unexpected panic when doing isNullRejected
 check (#22173) (#22327)

---
 expression/constant_fold.go    | 14 ++++++++------
 expression/constant_test.go    | 27 ---------------------------
 expression/integration_test.go | 25 +++++++++++++++++++++++++
 3 files changed, 33 insertions(+), 33 deletions(-)

diff --git a/expression/constant_fold.go b/expression/constant_fold.go
index c5810c8570387..6f84eefeaefb9 100644
--- a/expression/constant_fold.go
+++ b/expression/constant_fold.go
@@ -191,15 +191,17 @@ func foldConstant(expr Expression) (Expression, bool) {
 				return expr, isDeferredConst
 			}
 			if value.IsNull() {
-				if isDeferredConst {
-					return &Constant{Value: value, RetType: x.RetType, DeferredExpr: x}, true
-				}
+				// This Constant is created to compose the result expression of EvaluateExprWithNull when InNullRejectCheck
+				// is true. We just check whether the result expression is null or false and then let it die. Basically,
+				// the constant is used once briefly and will not be retained for a long time. Hence setting DeferredExpr
+				// of Constant to nil is ok.
 				return &Constant{Value: value, RetType: x.RetType}, false
 			}
 			if isTrue, err := value.ToBool(sc); err == nil && isTrue == 0 {
-				if isDeferredConst {
-					return &Constant{Value: value, RetType: x.RetType, DeferredExpr: x}, true
-				}
+				// This Constant is created to compose the result expression of EvaluateExprWithNull when InNullRejectCheck
+				// is true. We just check whether the result expression is null or false and then let it die. Basically,
+				// the constant is used once briefly and will not be retained for a long time. Hence setting DeferredExpr
+				// of Constant to nil is ok.
 				return &Constant{Value: value, RetType: x.RetType}, false
 			}
 			return expr, isDeferredConst
diff --git a/expression/constant_test.go b/expression/constant_test.go
index 64ae35e70c308..50ea87d010f7b 100644
--- a/expression/constant_test.go
+++ b/expression/constant_test.go
@@ -234,33 +234,6 @@ func (*testExpressionSuite) TestConstantFolding(c *C) {
 	}
 }
 
-func (*testExpressionSuite) TestDeferredExprNullConstantFold(c *C) {
-	nullConst := &Constant{
-		Value:        types.NewDatum(nil),
-		RetType:      types.NewFieldType(mysql.TypeTiny),
-		DeferredExpr: NewNull(),
-	}
-	tests := []struct {
-		condition Expression
-		deferred  string
-	}{
-		{
-			condition: newFunction(ast.LT, newColumn(0), nullConst),
-			deferred:  "lt(Column#0, <nil>)",
-		},
-	}
-	for _, tt := range tests {
-		comment := Commentf("different for expr %s", tt.condition)
-		sf, ok := tt.condition.(*ScalarFunction)
-		c.Assert(ok, IsTrue, comment)
-		sf.GetCtx().GetSessionVars().StmtCtx.InNullRejectCheck = true
-		newConds := FoldConstant(tt.condition)
-		newConst, ok := newConds.(*Constant)
-		c.Assert(ok, IsTrue, comment)
-		c.Assert(newConst.DeferredExpr.String(), Equals, tt.deferred, comment)
-	}
-}
-
 func (*testExpressionSuite) TestDeferredParamNotNull(c *C) {
 	ctx := mock.NewContext()
 	testTime := time.Now()
diff --git a/expression/integration_test.go b/expression/integration_test.go
index de33b1c0d9593..fac2606eb690e 100755
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -7336,3 +7336,28 @@ func (s *testIntegrationSuite) TestDatetimeUserVariable(c *C) {
 	tk.MustExec("set @@tidb_enable_vectorized_expression = true")
 	c.Check(tk.MustQuery("select @p").Rows()[0][0] != "", IsTrue)
 }
+
+func (s *testIntegrationSuite) TestIssue22098(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE `ta` (" +
+		"  `k` varchar(32) NOT NULL DEFAULT ' '," +
+		"  `c0` varchar(32) NOT NULL DEFAULT ' '," +
+		"  `c` varchar(18) NOT NULL DEFAULT ' '," +
+		"  `e0` varchar(1) NOT NULL DEFAULT ' '," +
+		"  PRIMARY KEY (`k`,`c0`,`c`)," +
+		"  KEY `idx` (`c`,`e0`)" +
+		") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin")
+	tk.MustExec("CREATE TABLE `tb` (" +
+		"  `k` varchar(32) NOT NULL DEFAULT ' '," +
+		"  `e` int(11) NOT NULL DEFAULT '0'," +
+		"  `i` int(11) NOT NULL DEFAULT '0'," +
+		"  `s` varchar(1) NOT NULL DEFAULT ' '," +
+		"  `c` varchar(50) NOT NULL DEFAULT ' '," +
+		"  PRIMARY KEY (`k`)" +
+		") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin")
+	tk.MustExec("prepare stmt from \"select a.* from ta a left join tb b on a.k = b.k where (a.k <> '000000' and ((b.s = ? and i = ? ) or (b.s = ? and e = ?) or (b.s not in(?, ?))) and b.c like '%1%') or (a.c <> '000000' and a.k = '000000')\"")
+	tk.MustExec("set @a=3;set @b=20200414;set @c='a';set @d=20200414;set @e=3;set @f='a';")
+	tk.MustQuery("execute stmt using @a,@b,@c,@d,@e,@f").Check(testkit.Rows())
+}