Append only time

connection.go

@@ -242,16 +242,12 @@ func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (strin
 				buf = append(buf, '0')
 			}
 		case time.Time:
-			if v.IsZero() {
-				buf = append(buf, "'0000-00-00'"...)
-			} else {
-				buf = append(buf, '\'')
-				buf, err = appendDateTime(buf, v.In(mc.cfg.Loc))
-				if err != nil {
-					return "", err
-				}
-				buf = append(buf, '\'')
+			buf = append(buf, '\'')
+			buf, err = appendTime(buf, v.In(mc.cfg.Loc))
+			if err != nil {
+				return "", err
 			}
+			buf = append(buf, '\'')
 		case json.RawMessage:
 			buf = append(buf, '\'')
 			if mc.status&statusNoBackslashEscapes == 0 {

packets.go

@@ -1113,13 +1113,9 @@ func (stmt *mysqlStmt) writeExecutePacket(args []driver.Value) error {
 				var a [64]byte
 				var b = a[:0]
 
-				if v.IsZero() {
-					b = append(b, "0000-00-00"...)
-				} else {
-					b, err = appendDateTime(b, v.In(mc.cfg.Loc))
-					if err != nil {
-						return err
-					}
+				b, err = appendTime(b, v.In(mc.cfg.Loc))
+				if err != nil {
+					return err
 				}
 
 				paramValues = appendLengthEncodedInteger(paramValues,

utils.go

@@ -276,12 +276,29 @@ func parseBinaryDateTime(num uint64, data []byte, loc *time.Location) (driver.Va
 	return nil, fmt.Errorf("invalid DATETIME packet length %d", num)
 }
 
+// appendTime serializes a time.Time t and appends it to buf.
+func appendTime(buf []byte, t time.Time) ([]byte, error) {
+	// this is the layout string for the "time of day" format of the MySQL TIME type
+	// see https://dev.mysql.com/doc/refman/8.0/en/time.html
+	const mysqlTimeLayout = "15:04:05"
+
+	switch {
+	case t.IsZero():
+		return append(buf, "0000-00-00"...), nil
+	case t.Year() == 0 && t.Month() == 1 && t.Day() == 1:
+		return t.AppendFormat(buf, mysqlTimeLayout), nil
+	default:
+		return appendDateTime(buf, t)
+	}
+}
+
+// appendDateTime is a special case of appendTime.
 func appendDateTime(buf []byte, t time.Time) ([]byte, error) {
 	year, month, day := t.Date()
 	hour, min, sec := t.Clock()
 	nsec := t.Nanosecond()
 
-	if year < 1 || year > 9999 {
+	if year < 0 || year > 9999 {
 		return buf, errors.New("year is not in the range [1, 9999]: " + strconv.Itoa(year)) // use errors.New instead of fmt.Errorf to avoid year escape to heap
 	}
 	year100 := year / 100

utils_test.go

@@ -295,7 +295,7 @@ func TestIsolationLevelMapping(t *testing.T) {
 	}
 }
 
-func TestAppendDateTime(t *testing.T) {
+func TestAppendTime(t *testing.T) {
 	tests := []struct {
 		t   time.Time
 		str string
@@ -333,23 +333,34 @@ func TestAppendDateTime(t *testing.T) {
 			str: "9999-12-31 23:59:59.999999999",
 		},
 		{
+			// zero date
 			t:   time.Date(1, 1, 1, 0, 0, 0, 0, time.UTC),
-			str: "0001-01-01",
+			str: "0000-00-00",
+		},
+		{
+			// valid date with year 0
+			t:   time.Date(0, 2, 2, 12, 34, 56, 0, time.UTC),
+			str: "0000-02-02 12:34:56",
+		},
+		{
+			// only time
+			t:   time.Date(0, 1, 1, 8, 30, 0, 0, time.UTC),
+			str: "08:30:00",
 		},
 	}
 	for _, v := range tests {
 		buf := make([]byte, 0, 32)
-		buf, _ = appendDateTime(buf, v.t)
+		buf, _ = appendTime(buf, v.t)
 		if str := string(buf); str != v.str {
 			t.Errorf("appendDateTime(%v), have: %s, want: %s", v.t, str, v.str)
 		}
 	}
 
 	// year out of range
 	{
-		v := time.Date(0, 1, 1, 0, 0, 0, 0, time.UTC)
+		v := time.Date(-1, 1, 1, 0, 0, 0, 0, time.UTC)
 		buf := make([]byte, 0, 32)
-		_, err := appendDateTime(buf, v)
+		_, err := appendTime(buf, v)
 		if err == nil {
 			t.Error("want an error")
 			return
@@ -358,7 +369,7 @@ func TestAppendDateTime(t *testing.T) {
 	{
 		v := time.Date(10000, 1, 1, 0, 0, 0, 0, time.UTC)
 		buf := make([]byte, 0, 32)
-		_, err := appendDateTime(buf, v)
+		_, err := appendTime(buf, v)
 		if err == nil {
 			t.Error("want an error")
 			return