forgejo/vendor/github.com/go-sql-driver/mysql/utils.go

869 lines
21 KiB
Go
Raw Normal View History

2016-11-03 23:16:01 +01:00
// Go MySQL Driver - A MySQL-Driver for Go's database/sql package
//
// Copyright 2012 The Go-MySQL-Driver Authors. All rights reserved.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at http://mozilla.org/MPL/2.0/.
package mysql
import (
"crypto/tls"
"database/sql"
2016-11-03 23:16:01 +01:00
"database/sql/driver"
"encoding/binary"
"errors"
2016-11-03 23:16:01 +01:00
"fmt"
"io"
"strconv"
2016-11-03 23:16:01 +01:00
"strings"
"sync"
"sync/atomic"
2016-11-03 23:16:01 +01:00
"time"
)
// Registry for custom tls.Configs
2016-11-03 23:16:01 +01:00
var (
tlsConfigLock sync.RWMutex
tlsConfigRegistry map[string]*tls.Config
2016-11-03 23:16:01 +01:00
)
// RegisterTLSConfig registers a custom tls.Config to be used with sql.Open.
// Use the key as a value in the DSN where tls=value.
//
// Note: The provided tls.Config is exclusively owned by the driver after
// registering it.
//
2016-11-03 23:16:01 +01:00
// rootCertPool := x509.NewCertPool()
// pem, err := ioutil.ReadFile("/path/ca-cert.pem")
// if err != nil {
// log.Fatal(err)
// }
// if ok := rootCertPool.AppendCertsFromPEM(pem); !ok {
// log.Fatal("Failed to append PEM.")
// }
// clientCert := make([]tls.Certificate, 0, 1)
// certs, err := tls.LoadX509KeyPair("/path/client-cert.pem", "/path/client-key.pem")
// if err != nil {
// log.Fatal(err)
// }
// clientCert = append(clientCert, certs)
// mysql.RegisterTLSConfig("custom", &tls.Config{
// RootCAs: rootCertPool,
// Certificates: clientCert,
// })
// db, err := sql.Open("mysql", "user@tcp(localhost:3306)/test?tls=custom")
//
func RegisterTLSConfig(key string, config *tls.Config) error {
if _, isBool := readBool(key); isBool || strings.ToLower(key) == "skip-verify" || strings.ToLower(key) == "preferred" {
2016-11-03 23:16:01 +01:00
return fmt.Errorf("key '%s' is reserved", key)
}
tlsConfigLock.Lock()
if tlsConfigRegistry == nil {
tlsConfigRegistry = make(map[string]*tls.Config)
2016-11-03 23:16:01 +01:00
}
tlsConfigRegistry[key] = config
tlsConfigLock.Unlock()
2016-11-03 23:16:01 +01:00
return nil
}
// DeregisterTLSConfig removes the tls.Config associated with key.
func DeregisterTLSConfig(key string) {
tlsConfigLock.Lock()
if tlsConfigRegistry != nil {
delete(tlsConfigRegistry, key)
2016-11-03 23:16:01 +01:00
}
tlsConfigLock.Unlock()
}
func getTLSConfigClone(key string) (config *tls.Config) {
tlsConfigLock.RLock()
if v, ok := tlsConfigRegistry[key]; ok {
config = v.Clone()
}
tlsConfigLock.RUnlock()
return
2016-11-03 23:16:01 +01:00
}
// Returns the bool value of the input.
// The 2nd return value indicates if the input was a valid bool value
func readBool(input string) (value bool, valid bool) {
switch input {
case "1", "true", "TRUE", "True":
return true, true
case "0", "false", "FALSE", "False":
return false, true
}
// Not a valid bool value
return
}
/******************************************************************************
* Time related utils *
******************************************************************************/
func parseDateTime(b []byte, loc *time.Location) (time.Time, error) {
const base = "0000-00-00 00:00:00.000000"
switch len(b) {
2016-11-03 23:16:01 +01:00
case 10, 19, 21, 22, 23, 24, 25, 26: // up to "YYYY-MM-DD HH:MM:SS.MMMMMM"
if string(b) == base[:len(b)] {
return time.Time{}, nil
2016-11-03 23:16:01 +01:00
}
year, err := parseByteYear(b)
if err != nil {
return time.Time{}, err
}
if year <= 0 {
year = 1
}
if b[4] != '-' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[4])
}
m, err := parseByte2Digits(b[5], b[6])
if err != nil {
return time.Time{}, err
}
if m <= 0 {
m = 1
}
month := time.Month(m)
if b[7] != '-' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[7])
}
day, err := parseByte2Digits(b[8], b[9])
if err != nil {
return time.Time{}, err
}
if day <= 0 {
day = 1
}
if len(b) == 10 {
return time.Date(year, month, day, 0, 0, 0, 0, loc), nil
}
if b[10] != ' ' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[10])
}
hour, err := parseByte2Digits(b[11], b[12])
if err != nil {
return time.Time{}, err
}
if b[13] != ':' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[13])
}
min, err := parseByte2Digits(b[14], b[15])
if err != nil {
return time.Time{}, err
}
if b[16] != ':' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[16])
}
sec, err := parseByte2Digits(b[17], b[18])
if err != nil {
return time.Time{}, err
}
if len(b) == 19 {
return time.Date(year, month, day, hour, min, sec, 0, loc), nil
}
if b[19] != '.' {
return time.Time{}, fmt.Errorf("bad value for field: `%c`", b[19])
}
nsec, err := parseByteNanoSec(b[20:])
if err != nil {
return time.Time{}, err
}
return time.Date(year, month, day, hour, min, sec, nsec, loc), nil
2016-11-03 23:16:01 +01:00
default:
return time.Time{}, fmt.Errorf("invalid time bytes: %s", b)
2016-11-03 23:16:01 +01:00
}
}
2016-11-03 23:16:01 +01:00
func parseByteYear(b []byte) (int, error) {
year, n := 0, 1000
for i := 0; i < 4; i++ {
v, err := bToi(b[i])
if err != nil {
return 0, err
}
year += v * n
n = n / 10
2016-11-03 23:16:01 +01:00
}
return year, nil
}
2016-11-03 23:16:01 +01:00
func parseByte2Digits(b1, b2 byte) (int, error) {
d1, err := bToi(b1)
if err != nil {
return 0, err
}
d2, err := bToi(b2)
if err != nil {
return 0, err
}
return d1*10 + d2, nil
}
func parseByteNanoSec(b []byte) (int, error) {
ns, digit := 0, 100000 // max is 6-digits
for i := 0; i < len(b); i++ {
v, err := bToi(b[i])
if err != nil {
return 0, err
}
ns += v * digit
digit /= 10
}
// nanoseconds has 10-digits. (needs to scale digits)
// 10 - 6 = 4, so we have to multiple 1000.
return ns * 1000, nil
}
func bToi(b byte) (int, error) {
if b < '0' || b > '9' {
return 0, errors.New("not [0-9]")
}
return int(b - '0'), nil
2016-11-03 23:16:01 +01:00
}
func parseBinaryDateTime(num uint64, data []byte, loc *time.Location) (driver.Value, error) {
switch num {
case 0:
return time.Time{}, nil
case 4:
return time.Date(
int(binary.LittleEndian.Uint16(data[:2])), // year
time.Month(data[2]), // month
int(data[3]), // day
0, 0, 0, 0,
loc,
), nil
case 7:
return time.Date(
int(binary.LittleEndian.Uint16(data[:2])), // year
time.Month(data[2]), // month
int(data[3]), // day
int(data[4]), // hour
int(data[5]), // minutes
int(data[6]), // seconds
0,
loc,
), nil
case 11:
return time.Date(
int(binary.LittleEndian.Uint16(data[:2])), // year
time.Month(data[2]), // month
int(data[3]), // day
int(data[4]), // hour
int(data[5]), // minutes
int(data[6]), // seconds
int(binary.LittleEndian.Uint32(data[7:11]))*1000, // nanoseconds
loc,
), nil
}
return nil, fmt.Errorf("invalid DATETIME packet length %d", num)
}
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 {
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
year1 := year % 100
var localBuf [len("2006-01-02T15:04:05.999999999")]byte // does not escape
localBuf[0], localBuf[1], localBuf[2], localBuf[3] = digits10[year100], digits01[year100], digits10[year1], digits01[year1]
localBuf[4] = '-'
localBuf[5], localBuf[6] = digits10[month], digits01[month]
localBuf[7] = '-'
localBuf[8], localBuf[9] = digits10[day], digits01[day]
if hour == 0 && min == 0 && sec == 0 && nsec == 0 {
return append(buf, localBuf[:10]...), nil
}
localBuf[10] = ' '
localBuf[11], localBuf[12] = digits10[hour], digits01[hour]
localBuf[13] = ':'
localBuf[14], localBuf[15] = digits10[min], digits01[min]
localBuf[16] = ':'
localBuf[17], localBuf[18] = digits10[sec], digits01[sec]
if nsec == 0 {
return append(buf, localBuf[:19]...), nil
}
nsec100000000 := nsec / 100000000
nsec1000000 := (nsec / 1000000) % 100
nsec10000 := (nsec / 10000) % 100
nsec100 := (nsec / 100) % 100
nsec1 := nsec % 100
localBuf[19] = '.'
// milli second
localBuf[20], localBuf[21], localBuf[22] =
digits01[nsec100000000], digits10[nsec1000000], digits01[nsec1000000]
// micro second
localBuf[23], localBuf[24], localBuf[25] =
digits10[nsec10000], digits01[nsec10000], digits10[nsec100]
// nano second
localBuf[26], localBuf[27], localBuf[28] =
digits01[nsec100], digits10[nsec1], digits01[nsec1]
// trim trailing zeros
n := len(localBuf)
for n > 0 && localBuf[n-1] == '0' {
n--
}
return append(buf, localBuf[:n]...), nil
}
2016-11-03 23:16:01 +01:00
// zeroDateTime is used in formatBinaryDateTime to avoid an allocation
// if the DATE or DATETIME has the zero value.
// It must never be changed.
// The current behavior depends on database/sql copying the result.
var zeroDateTime = []byte("0000-00-00 00:00:00.000000")
const digits01 = "0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789"
const digits10 = "0000000000111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999"
func appendMicrosecs(dst, src []byte, decimals int) []byte {
if decimals <= 0 {
return dst
2016-11-03 23:16:01 +01:00
}
if len(src) == 0 {
return append(dst, ".000000"[:decimals+1]...)
2016-11-03 23:16:01 +01:00
}
2016-11-03 23:16:01 +01:00
microsecs := binary.LittleEndian.Uint32(src[:4])
p1 := byte(microsecs / 10000)
2016-11-03 23:16:01 +01:00
microsecs -= 10000 * uint32(p1)
p2 := byte(microsecs / 100)
2016-11-03 23:16:01 +01:00
microsecs -= 100 * uint32(p2)
p3 := byte(microsecs)
switch decimals {
2016-11-03 23:16:01 +01:00
default:
return append(dst, '.',
digits10[p1], digits01[p1],
digits10[p2], digits01[p2],
digits10[p3], digits01[p3],
)
2016-11-03 23:16:01 +01:00
case 1:
return append(dst, '.',
digits10[p1],
)
2016-11-03 23:16:01 +01:00
case 2:
return append(dst, '.',
digits10[p1], digits01[p1],
)
2016-11-03 23:16:01 +01:00
case 3:
return append(dst, '.',
digits10[p1], digits01[p1],
digits10[p2],
)
2016-11-03 23:16:01 +01:00
case 4:
return append(dst, '.',
digits10[p1], digits01[p1],
digits10[p2], digits01[p2],
)
2016-11-03 23:16:01 +01:00
case 5:
return append(dst, '.',
digits10[p1], digits01[p1],
digits10[p2], digits01[p2],
digits10[p3],
)
2016-11-03 23:16:01 +01:00
}
}
func formatBinaryDateTime(src []byte, length uint8) (driver.Value, error) {
// length expects the deterministic length of the zero value,
// negative time and 100+ hours are automatically added if needed
if len(src) == 0 {
return zeroDateTime[:length], nil
}
var dst []byte // return value
var p1, p2, p3 byte // current digit pair
switch length {
case 10, 19, 21, 22, 23, 24, 25, 26:
default:
t := "DATE"
if length > 10 {
t += "TIME"
}
return nil, fmt.Errorf("illegal %s length %d", t, length)
}
switch len(src) {
case 4, 7, 11:
default:
t := "DATE"
if length > 10 {
t += "TIME"
}
return nil, fmt.Errorf("illegal %s packet length %d", t, len(src))
}
dst = make([]byte, 0, length)
// start with the date
year := binary.LittleEndian.Uint16(src[:2])
pt := year / 100
p1 = byte(year - 100*uint16(pt))
p2, p3 = src[2], src[3]
dst = append(dst,
digits10[pt], digits01[pt],
digits10[p1], digits01[p1], '-',
digits10[p2], digits01[p2], '-',
digits10[p3], digits01[p3],
)
if length == 10 {
return dst, nil
}
if len(src) == 4 {
return append(dst, zeroDateTime[10:length]...), nil
}
dst = append(dst, ' ')
p1 = src[4] // hour
src = src[5:]
// p1 is 2-digit hour, src is after hour
p2, p3 = src[0], src[1]
dst = append(dst,
digits10[p1], digits01[p1], ':',
digits10[p2], digits01[p2], ':',
digits10[p3], digits01[p3],
)
return appendMicrosecs(dst, src[2:], int(length)-20), nil
}
func formatBinaryTime(src []byte, length uint8) (driver.Value, error) {
// length expects the deterministic length of the zero value,
// negative time and 100+ hours are automatically added if needed
if len(src) == 0 {
return zeroDateTime[11 : 11+length], nil
}
var dst []byte // return value
switch length {
case
8, // time (can be up to 10 when negative and 100+ hours)
10, 11, 12, 13, 14, 15: // time with fractional seconds
default:
return nil, fmt.Errorf("illegal TIME length %d", length)
}
switch len(src) {
case 8, 12:
default:
return nil, fmt.Errorf("invalid TIME packet length %d", len(src))
}
// +2 to enable negative time and 100+ hours
dst = make([]byte, 0, length+2)
if src[0] == 1 {
dst = append(dst, '-')
}
days := binary.LittleEndian.Uint32(src[1:5])
hours := int64(days)*24 + int64(src[5])
if hours >= 100 {
dst = strconv.AppendInt(dst, hours, 10)
} else {
dst = append(dst, digits10[hours], digits01[hours])
}
min, sec := src[6], src[7]
dst = append(dst, ':',
digits10[min], digits01[min], ':',
digits10[sec], digits01[sec],
)
return appendMicrosecs(dst, src[8:], int(length)-9), nil
}
2016-11-03 23:16:01 +01:00
/******************************************************************************
* Convert from and to bytes *
******************************************************************************/
func uint64ToBytes(n uint64) []byte {
return []byte{
byte(n),
byte(n >> 8),
byte(n >> 16),
byte(n >> 24),
byte(n >> 32),
byte(n >> 40),
byte(n >> 48),
byte(n >> 56),
}
}
func uint64ToString(n uint64) []byte {
var a [20]byte
i := 20
// U+0030 = 0
// ...
// U+0039 = 9
var q uint64
for n >= 10 {
i--
q = n / 10
a[i] = uint8(n-q*10) + 0x30
n = q
}
i--
a[i] = uint8(n) + 0x30
return a[i:]
}
// treats string value as unsigned integer representation
func stringToInt(b []byte) int {
val := 0
for i := range b {
val *= 10
val += int(b[i] - 0x30)
}
return val
}
// returns the string read as a bytes slice, wheter the value is NULL,
// the number of bytes read and an error, in case the string is longer than
// the input slice
func readLengthEncodedString(b []byte) ([]byte, bool, int, error) {
// Get length
num, isNull, n := readLengthEncodedInteger(b)
if num < 1 {
return b[n:n], isNull, n, nil
}
n += int(num)
// Check data length
if len(b) >= n {
return b[n-int(num) : n : n], false, n, nil
2016-11-03 23:16:01 +01:00
}
return nil, false, n, io.EOF
}
// returns the number of bytes skipped and an error, in case the string is
// longer than the input slice
func skipLengthEncodedString(b []byte) (int, error) {
// Get length
num, _, n := readLengthEncodedInteger(b)
if num < 1 {
return n, nil
}
n += int(num)
// Check data length
if len(b) >= n {
return n, nil
}
return n, io.EOF
}
// returns the number read, whether the value is NULL and the number of bytes read
func readLengthEncodedInteger(b []byte) (uint64, bool, int) {
// See issue #349
if len(b) == 0 {
return 0, true, 1
}
switch b[0] {
2016-11-03 23:16:01 +01:00
// 251: NULL
case 0xfb:
return 0, true, 1
// 252: value of following 2
case 0xfc:
return uint64(b[1]) | uint64(b[2])<<8, false, 3
// 253: value of following 3
case 0xfd:
return uint64(b[1]) | uint64(b[2])<<8 | uint64(b[3])<<16, false, 4
// 254: value of following 8
case 0xfe:
return uint64(b[1]) | uint64(b[2])<<8 | uint64(b[3])<<16 |
uint64(b[4])<<24 | uint64(b[5])<<32 | uint64(b[6])<<40 |
uint64(b[7])<<48 | uint64(b[8])<<56,
false, 9
}
// 0-250: value of first byte
return uint64(b[0]), false, 1
}
// encodes a uint64 value and appends it to the given bytes slice
func appendLengthEncodedInteger(b []byte, n uint64) []byte {
switch {
case n <= 250:
return append(b, byte(n))
case n <= 0xffff:
return append(b, 0xfc, byte(n), byte(n>>8))
case n <= 0xffffff:
return append(b, 0xfd, byte(n), byte(n>>8), byte(n>>16))
}
return append(b, 0xfe, byte(n), byte(n>>8), byte(n>>16), byte(n>>24),
byte(n>>32), byte(n>>40), byte(n>>48), byte(n>>56))
}
// reserveBuffer checks cap(buf) and expand buffer to len(buf) + appendSize.
// If cap(buf) is not enough, reallocate new buffer.
func reserveBuffer(buf []byte, appendSize int) []byte {
newSize := len(buf) + appendSize
if cap(buf) < newSize {
// Grow buffer exponentially
newBuf := make([]byte, len(buf)*2+appendSize)
copy(newBuf, buf)
buf = newBuf
}
return buf[:newSize]
}
// escapeBytesBackslash escapes []byte with backslashes (\)
// This escapes the contents of a string (provided as []byte) by adding backslashes before special
// characters, and turning others into specific escape sequences, such as
// turning newlines into \n and null bytes into \0.
// https://github.com/mysql/mysql-server/blob/mysql-5.7.5/mysys/charset.c#L823-L932
func escapeBytesBackslash(buf, v []byte) []byte {
pos := len(buf)
buf = reserveBuffer(buf, len(v)*2)
for _, c := range v {
switch c {
case '\x00':
buf[pos] = '\\'
buf[pos+1] = '0'
pos += 2
case '\n':
buf[pos] = '\\'
buf[pos+1] = 'n'
pos += 2
case '\r':
buf[pos] = '\\'
buf[pos+1] = 'r'
pos += 2
case '\x1a':
buf[pos] = '\\'
buf[pos+1] = 'Z'
pos += 2
case '\'':
buf[pos] = '\\'
buf[pos+1] = '\''
pos += 2
case '"':
buf[pos] = '\\'
buf[pos+1] = '"'
pos += 2
case '\\':
buf[pos] = '\\'
buf[pos+1] = '\\'
pos += 2
default:
buf[pos] = c
pos++
}
}
return buf[:pos]
}
// escapeStringBackslash is similar to escapeBytesBackslash but for string.
func escapeStringBackslash(buf []byte, v string) []byte {
pos := len(buf)
buf = reserveBuffer(buf, len(v)*2)
for i := 0; i < len(v); i++ {
c := v[i]
switch c {
case '\x00':
buf[pos] = '\\'
buf[pos+1] = '0'
pos += 2
case '\n':
buf[pos] = '\\'
buf[pos+1] = 'n'
pos += 2
case '\r':
buf[pos] = '\\'
buf[pos+1] = 'r'
pos += 2
case '\x1a':
buf[pos] = '\\'
buf[pos+1] = 'Z'
pos += 2
case '\'':
buf[pos] = '\\'
buf[pos+1] = '\''
pos += 2
case '"':
buf[pos] = '\\'
buf[pos+1] = '"'
pos += 2
case '\\':
buf[pos] = '\\'
buf[pos+1] = '\\'
pos += 2
default:
buf[pos] = c
pos++
}
}
return buf[:pos]
}
// escapeBytesQuotes escapes apostrophes in []byte by doubling them up.
// This escapes the contents of a string by doubling up any apostrophes that
// it contains. This is used when the NO_BACKSLASH_ESCAPES SQL_MODE is in
// effect on the server.
// https://github.com/mysql/mysql-server/blob/mysql-5.7.5/mysys/charset.c#L963-L1038
func escapeBytesQuotes(buf, v []byte) []byte {
pos := len(buf)
buf = reserveBuffer(buf, len(v)*2)
for _, c := range v {
if c == '\'' {
buf[pos] = '\''
buf[pos+1] = '\''
pos += 2
} else {
buf[pos] = c
pos++
}
}
return buf[:pos]
}
// escapeStringQuotes is similar to escapeBytesQuotes but for string.
func escapeStringQuotes(buf []byte, v string) []byte {
pos := len(buf)
buf = reserveBuffer(buf, len(v)*2)
for i := 0; i < len(v); i++ {
c := v[i]
if c == '\'' {
buf[pos] = '\''
buf[pos+1] = '\''
pos += 2
} else {
buf[pos] = c
pos++
}
}
return buf[:pos]
}
/******************************************************************************
* Sync utils *
******************************************************************************/
// noCopy may be embedded into structs which must not be copied
// after the first use.
//
// See https://github.com/golang/go/issues/8005#issuecomment-190753527
// for details.
type noCopy struct{}
// Lock is a no-op used by -copylocks checker from `go vet`.
func (*noCopy) Lock() {}
// atomicBool is a wrapper around uint32 for usage as a boolean value with
// atomic access.
type atomicBool struct {
_noCopy noCopy
value uint32
}
// IsSet returns whether the current boolean value is true
func (ab *atomicBool) IsSet() bool {
return atomic.LoadUint32(&ab.value) > 0
}
// Set sets the value of the bool regardless of the previous value
func (ab *atomicBool) Set(value bool) {
if value {
atomic.StoreUint32(&ab.value, 1)
} else {
atomic.StoreUint32(&ab.value, 0)
}
}
// TrySet sets the value of the bool and returns whether the value changed
func (ab *atomicBool) TrySet(value bool) bool {
if value {
return atomic.SwapUint32(&ab.value, 1) == 0
}
return atomic.SwapUint32(&ab.value, 0) > 0
}
// atomicError is a wrapper for atomically accessed error values
type atomicError struct {
_noCopy noCopy
value atomic.Value
}
// Set sets the error value regardless of the previous value.
// The value must not be nil
func (ae *atomicError) Set(value error) {
ae.value.Store(value)
}
// Value returns the current error value
func (ae *atomicError) Value() error {
if v := ae.value.Load(); v != nil {
// this will panic if the value doesn't implement the error interface
return v.(error)
}
return nil
}
func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
dargs := make([]driver.Value, len(named))
for n, param := range named {
if len(param.Name) > 0 {
// TODO: support the use of Named Parameters #561
return nil, errors.New("mysql: driver does not support the use of Named Parameters")
}
dargs[n] = param.Value
}
return dargs, nil
}
func mapIsolationLevel(level driver.IsolationLevel) (string, error) {
switch sql.IsolationLevel(level) {
case sql.LevelRepeatableRead:
return "REPEATABLE READ", nil
case sql.LevelReadCommitted:
return "READ COMMITTED", nil
case sql.LevelReadUncommitted:
return "READ UNCOMMITTED", nil
case sql.LevelSerializable:
return "SERIALIZABLE", nil
default:
return "", fmt.Errorf("mysql: unsupported isolation level: %v", level)
}
}