expression: rewrite builtin function: TO_DAYS (pingcap#4161)

expression/builtin_time.go

@@ -2803,35 +2803,34 @@ func (c *toDaysFunctionClass) getFunction(args []Expression, ctx context.Context
 	if err := c.verifyArgs(args); err != nil {
 		return nil, errors.Trace(err)
 	}
-	sig := &builtinToDaysSig{newBaseBuiltinFunc(args, ctx)}
+	bf, err := newBaseBuiltinFuncWithTp(args, ctx, tpInt, tpTime)
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
+	sig := &builtinToDaysSig{baseIntBuiltinFunc{bf}}
 	return sig.setSelf(sig), nil
 }
 
 type builtinToDaysSig struct {
-	baseBuiltinFunc
+	baseIntBuiltinFunc
 }
 
-// eval evals a builtinToDaysSig.
+// evalInt evals a builtinToDaysSig.
 // See https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_to-days
-func (b *builtinToDaysSig) eval(row []types.Datum) (d types.Datum, err error) {
-	args, err := b.evalArgs(row)
-	if err != nil {
-		return d, errors.Trace(err)
-	}
-	if args[0].IsNull() {
-		return
-	}
+func (b *builtinToDaysSig) evalInt(row []types.Datum) (int64, bool, error) {
 	sc := b.ctx.GetSessionVars().StmtCtx
-	date, err := convertDatumToTime(sc, args[0])
+	arg, isNull, err := b.args[0].EvalTime(row, sc)
+	if isNull || err != nil {
+		return 0, true, errorOrWarning(err, b.ctx)
+	}
 	if err != nil {
-		return d, errorOrWarning(err, b.ctx)
+		return 0, true, errorOrWarning(err, b.ctx)
 	}
-	ret := types.TimestampDiff("DAY", types.ZeroDate, date)
+	ret := types.TimestampDiff("DAY", types.ZeroDate, arg)
 	if ret == 0 {
-		return d, errorOrWarning(types.ErrInvalidTimeFormat, b.ctx)
+		return 0, true, errorOrWarning(types.ErrInvalidTimeFormat, b.ctx)
 	}
-	d.SetInt64(ret)
-	return
+	return ret, false, nil
 }
 
 type toSecondsFunctionClass struct {

expression/builtin_time_test.go

@@ -1483,6 +1483,7 @@ func (s *testEvaluatorSuite) TestToDays(c *C) {
 	for _, test := range tests {
 		t := []types.Datum{types.NewDatum(test.param)}
 		f, err := fc.getFunction(datumsToConstants(t), s.ctx)
+		c.Assert(f.isDeterministic(), IsTrue)
 		c.Assert(err, IsNil)
 		d, err := f.eval(nil)
 		c.Assert(err, IsNil)
@@ -1498,6 +1499,7 @@ func (s *testEvaluatorSuite) TestToDays(c *C) {
 	for _, i := range testsNull {
 		t := []types.Datum{types.NewDatum(i)}
 		f, err := fc.getFunction(datumsToConstants(t), s.ctx)
+		c.Assert(f.isDeterministic(), IsTrue)
 		c.Assert(err, IsNil)
 		d, err := f.eval(nil)
 		c.Assert(err, IsNil)

expression/integration_test.go

@@ -838,6 +838,8 @@ func (s *testIntegrationSuite) TestTimeBuiltin(c *C) {
 	result.Check(testkit.Rows("<nil>"))
 	result = tk.MustQuery("select timediff('2014-1-2 12:00:00', '2014-1-1 12:00:00');")
 	result.Check(testkit.Rows("24:00:00"))
+	result = tk.MustQuery("select to_days(950501), to_days('2007-10-07'), to_days('2007-10-07 00:00:59'), to_days('0000-01-01')")
+	result.Check(testkit.Rows("728779 733321 733321 1"))
 
 	// fixed issue #3986
 	tk.MustExec("SET SQL_MODE='NO_ENGINE_SUBSTITUTION';")

plan/typeinfer_test.go

@@ -82,6 +82,7 @@ func (s *testPlanSuite) TestInferType(c *C) {
 	tests = append(tests, s.createTestCase4CompareFuncs()...)
 	tests = append(tests, s.createTestCase4Miscellaneous()...)
 	tests = append(tests, s.createTestCase4OpFuncs()...)
+	tests = append(tests, s.createTestCase4TimeFuncs()...)
 
 	for _, tt := range tests {
 		ctx := testKit.Se.(context.Context)
@@ -689,3 +690,9 @@ func (s *testPlanSuite) createTestCase4OpFuncs() []typeInferTestCase {
 		{"1844674.1  is false", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, 1, 0},
 	}
 }
+
+func (s *testPlanSuite) createTestCase4TimeFuncs() []typeInferTestCase {
+	return []typeInferTestCase{
+		{"to_days(c_char)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, 20, 0},
+	}
+}