add String() for FieldValue (go-mysql-org#825)

* add String() for FieldValue Signed-off-by: lance6716 <lance6716@gmail.com> * fix lint Signed-off-by: lance6716 <lance6716@gmail.com> * escape Signed-off-by: lance6716 <lance6716@gmail.com> --------- Signed-off-by: lance6716 <lance6716@gmail.com>

Author: lance6716

client/client_test.go

@@ -423,3 +423,71 @@ func (s *clientTestSuite) TestStmt_Trans() {
 str, _ = r.GetString(0, 0)
 require.Equal(s.T(), `abc`, str)
 }
+
+func (s *clientTestSuite) TestFieldValueString() {
+_, err := s.c.Execute(
+`
+CREATE TABLE field_value_test (
+ c_int int,
+ c_bit bit(8),
+ c_tinyint_u tinyint unsigned,
+ c_decimal decimal(10, 5),
+ c_float float(10),
+ c_date date,
+ c_datetime datetime(3),
+ c_timestamp timestamp(4),
+ c_time time(5),
+ c_year year,
+ c_char char(10),
+ c_varchar varchar(10),
+ c_binary binary(10),
+ c_varbinary varbinary(10),
+ c_blob blob,
+ c_enum enum('a', 'b', 'c'),
+ c_set set('a', 'b', 'c'),
+ c_json json,
+ c_null int
+)`)
+require.NoError(s.T(), err)
+s.T().Cleanup(func() {
+_, _ = s.c.Execute(
+`DROP TABLE field_value_test`)
+})
+
+_, err = s.c.Execute(`
+INSERT INTO field_value_test VALUES (
+ 1, 2, 3, 4.5, 6.7, 
+ '2019-01-01', '2019-01-01 01:01:01.123', '2019-01-01 01:01:01.1234', '01:01:01.12345', 2019,
+ 'cha\'r', 'varchar', 'binary', 'varbinary', 'blob', 'a', 'a,b', '{"a": 1}',
+ NULL
+)`)
+require.NoError(s.T(), err)
+
+result, err := s.c.Execute(`SELECT * FROM field_value_test`)
+require.NoError(s.T(), err)
+require.Len(s.T(), result.Values, 1)
+expected := []string{
+`1`, "'\x02'", `3`, `'4.50000'`, `6.7`,
+`'2019-01-01'`, `'2019-01-01 01:01:01.123'`, `'2019-01-01 01:01:01.1234'`, `'01:01:01.12345'`, `2019`,
+`'cha\'r'`, `'varchar'`, "'binary\x00\x00\x00\x00'", `'varbinary'`, `'blob'`, `'a'`, `'a,b'`, `'{"a": 1}'`,
+`NULL`,
+}
+for i, v := range result.Values[0] {
+require.Equal(s.T(), expected[i], v.String())
+}
+
+// test can directly use to build a SQL, though it's not safe in most cases
+sql := fmt.Sprintf("INSERT INTO field_value_test VALUES (%s)", strings.Join(expected, ","))
+_, err = s.c.Execute(sql)
+require.NoError(s.T(), err)
+result, err = s.c.Execute(`SELECT * FROM field_value_test`)
+require.NoError(s.T(), err)
+// check again, everything is same
+require.Len(s.T(), result.Values, 2)
+for i, v := range result.Values[0] {
+require.Equal(s.T(), expected[i], v.String())
+}
+for i, v := range result.Values[1] {
+require.Equal(s.T(), expected[i], v.String())
+}
+}

mysql/field.go

@@ -2,6 +2,9 @@ package mysql
 
 import (
 "encoding/binary"
+"fmt"
+"strconv"
+"strings"
 
 "github.com/go-mysql-org/go-mysql/utils"
 )
@@ -210,3 +213,31 @@ func (fv *FieldValue) Value() interface{} {
 return nil
 }
 }
+
+// String returns a MySQL literal string that equals the value.
+func (fv *FieldValue) String() string {
+switch fv.Type {
+case FieldValueTypeNull:
+return "NULL"
+case FieldValueTypeUnsigned:
+return strconv.FormatUint(fv.AsUint64(), 10)
+case FieldValueTypeSigned:
+return strconv.FormatInt(fv.AsInt64(), 10)
+case FieldValueTypeFloat:
+return strconv.FormatFloat(fv.AsFloat64(), 'f', -1, 64)
+case FieldValueTypeString:
+b := strings.Builder{}
+b.Grow(len(fv.str) + 2)
+b.WriteByte('\'')
+for i := range fv.str {
+if fv.str[i] == '\'' {
+b.WriteByte('\\')
+}
+b.WriteByte(fv.str[i])
+}
+b.WriteByte('\'')
+return b.String()
+default:
+return fmt.Sprintf("unknown type %d of FieldValue", fv.Type)
+}
+}