expression: fix issue that TimeIsNull is not compatible with MySQL

expression/builtin_op.go

@@ -799,7 +799,12 @@ func (c *isNullFunctionClass) getFunction(ctx sessionctx.Context, args []Express
 		sig = &builtinRealIsNullSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_RealIsNull)
 	case types.ETDatetime:
-		sig = &builtinTimeIsNullSig{bf}
+		isNotNull := false
+		_, isCol := args[0].(*Column)
+		if isCol && mysql.HasNotNullFlag(args[0].GetType().Flag) {
+			isNotNull = true
+		}
+		sig = &builtinTimeIsNullSig{bf, isNotNull}
 		sig.setPbCode(tipb.ScalarFuncSig_TimeIsNull)
 	case types.ETDuration:
 		sig = &builtinDurationIsNullSig{bf}
@@ -900,15 +905,21 @@ func (b *builtinStringIsNullSig) evalInt(row chunk.Row) (int64, bool, error) {
 
 type builtinTimeIsNullSig struct {
 	baseBuiltinFunc
+	isNotNull bool
 }
 
 func (b *builtinTimeIsNullSig) Clone() builtinFunc {
 	newSig := &builtinTimeIsNullSig{}
 	newSig.cloneFrom(&b.baseBuiltinFunc)
+	newSig.isNotNull = b.isNotNull
 	return newSig
 }
 
 func (b *builtinTimeIsNullSig) evalInt(row chunk.Row) (int64, bool, error) {
-	_, isNull, err := b.args[0].EvalTime(b.ctx, row)
-	return evalIsNull(isNull, err)
+	//	Description below are from MySQL document:
+	//		For DATE and DATETIME columns that are declared as NOT NULL,
+	//		you can find the special date '0000-00-00' by using a statement like this:
+	//		"SELECT * FROM tbl_name WHERE date_column IS NULL"
+	t, isNull, err := b.args[0].EvalTime(b.ctx, row)
+	return evalIsNull(isNull || (b.isNotNull && t.IsZero()), err)
 }

expression/distsql_builtin.go

@@ -39,11 +39,11 @@ func pbTypeToFieldType(tp *tipb.FieldType) *types.FieldType {
 	}
 }
 
-func getSignatureByPB(ctx sessionctx.Context, sigCode tipb.ScalarFuncSig, tp *tipb.FieldType, args []Expression) (f builtinFunc, e error) {
-	fieldTp := pbTypeToFieldType(tp)
+func getSignatureByPB(ctx sessionctx.Context, expr *tipb.Expr, args []Expression) (f builtinFunc, e error) {
+	fieldTp := pbTypeToFieldType(expr.FieldType)
 	base := newBaseBuiltinFunc(ctx, args)
 	base.tp = fieldTp
-	switch sigCode {
+	switch expr.GetSig() {
 	case tipb.ScalarFuncSig_CastIntAsInt:
 		f = &builtinCastIntAsIntSig{newBaseBuiltinCastFunc(base, false)}
 	case tipb.ScalarFuncSig_CastRealAsInt:
@@ -336,7 +336,12 @@ func getSignatureByPB(ctx sessionctx.Context, sigCode tipb.ScalarFuncSig, tp *ti
 	case tipb.ScalarFuncSig_RealIsNull:
 		f = &builtinRealIsNullSig{base}
 	case tipb.ScalarFuncSig_TimeIsNull:
-		f = &builtinTimeIsNullSig{base}
+		isNotNull := false
+		if len(expr.Children) > 0 && expr.Children[0].Tp == tipb.ExprType_ColumnRef && mysql.HasNotNullFlag(uint(expr.Children[0].FieldType.Flag)) {
+			isNotNull = true
+		}
+
+		f = &builtinTimeIsNullSig{base, isNotNull}
 	case tipb.ScalarFuncSig_StringIsNull:
 		f = &builtinStringIsNullSig{base}
 	case tipb.ScalarFuncSig_IntIsNull:
@@ -466,16 +471,16 @@ func getSignatureByPB(ctx sessionctx.Context, sigCode tipb.ScalarFuncSig, tp *ti
 		f = &builtinDateFormatSig{base}
 
 	default:
-		e = errFunctionNotExists.GenWithStackByArgs("FUNCTION", sigCode)
+		e = errFunctionNotExists.GenWithStackByArgs("FUNCTION", expr.GetSig())
 		return nil, e
 	}
 	return f, nil
 }
 
-func newDistSQLFunctionBySig(sc *stmtctx.StatementContext, sigCode tipb.ScalarFuncSig, tp *tipb.FieldType, args []Expression) (Expression, error) {
+func newDistSQLFunctionBySig(sc *stmtctx.StatementContext, expr *tipb.Expr, args []Expression) (Expression, error) {
 	ctx := mock.NewContext()
 	ctx.GetSessionVars().StmtCtx = sc
-	f, err := getSignatureByPB(ctx, sigCode, tp, args)
+	f, err := getSignatureByPB(ctx, expr, args)
 	if err != nil {
 		return nil, err
 	}
@@ -541,7 +546,8 @@ func PBToExpr(expr *tipb.Expr, tps []*types.FieldType, sc *stmtctx.StatementCont
 		}
 		args = append(args, arg)
 	}
-	return newDistSQLFunctionBySig(sc, expr.Sig, expr.FieldType, args)
+
+	return newDistSQLFunctionBySig(sc, expr, args)
 }
 
 func convertTime(data []byte, ftPB *tipb.FieldType, tz *time.Location) (*Constant, error) {

expression/integration_test.go

@@ -4404,6 +4404,31 @@ func (s *testIntegrationSuite) TestExprPushdownBlacklist(c *C) {
 	tk.MustQuery(`select * from mysql.expr_pushdown_blacklist`).Check(testkit.Rows())
 }
 
+func (s *testIntegrationSuite) TestIssue9763(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+
+	tk.MustExec(`drop table if exists t1;`)
+	tk.MustExec(`CREATE TABLE t1 (a datetime not null);`)
+	tk.MustExec(`insert ignore into t1 values (0);`)
+	tk.MustQuery(`select * from t1 where a is null;`).Check(testkit.Rows(`0000-00-00 00:00:00`))
+
+	tk.MustExec(`drop table if exists t2;`)
+	tk.MustExec(`CREATE TABLE t2 (a date not null);`)
+	tk.MustExec(`insert ignore into t2 values (0);`)
+	tk.MustQuery(`select * from t2 where a is null;`).Check(testkit.Rows(`0000-00-00`))
+
+	tk.MustExec(`drop table if exists t3;`)
+	tk.MustExec(`CREATE TABLE t3 (a datetime);`)
+	tk.MustExec(`insert ignore into t3 values (0);`)
+	c.Assert(len(tk.MustQuery(`select * from t3 where a is null;`).Rows()), Equals, 0)
+
+	tk.MustExec(`drop table if exists t4;`)
+	tk.MustExec(`CREATE TABLE t4 (a date);`)
+	tk.MustExec(`insert ignore into t4 values (0);`)
+	c.Assert(len(tk.MustQuery(`select * from t4 where a is null;`).Rows()), Equals, 0)
+}
+
 func (s *testIntegrationSuite) TestIssue10804(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustQuery(`SELECT @@information_schema_stats_expiry`).Check(testkit.Rows(`86400`))