Go-MySQL-Driver

A MySQL-Driver for Go's database/sql package

• Features
• Requirements
• Installation
• Usage
  • DSN (Data Source Name)
    • Password
    • Protocol
    • Address
    • Parameters
    • Examples
  • Connection pool and timeouts
  • context.Context Support
  • ColumnType Support
  • LOAD DATA LOCAL INFILE support
  • time.Time support
  • Unicode support
• Testing / Development
• License

Features

• Lightweight and fast
• Native Go implementation. No C-bindings, just pure Go
• Connections over TCP/IPv4, TCP/IPv6, Unix domain sockets or custom protocols
• Automatic handling of broken connections
• Automatic Connection Pooling (by database/sql package)
• Supports queries larger than 16MB
• Full sql.RawBytes support.
• Intelligent LONG DATA handling in prepared statements
• Secure LOAD DATA LOCAL INFILE support with file allowlisting and io.Reader support
• Optional time.Time parsing
• Optional placeholder interpolation

Requirements

• Go 1.20 or higher. We aim to support the 3 latest versions of Go.
• MySQL (5.7+) and MariaDB (10.5+) are supported.
• TiDB is supported by PingCAP.
  • Do not ask questions about TiDB in our issue tracker or forum.
  • Document
  • Forum
• go-mysql would work with Percona Server, Google CloudSQL or Sphinx (2.2.3+).
  • Maintainers won't support them. Do not expect issues are investigated and resolved by maintainers.
  • Investigate issues yourself and please send a pull request to fix it.

Installation

Simple install the package to your $GOPATH with the go tool from shell:

go get -u github.com/go-sql-driver/mysql

Make sure Git is installed on your machine and in your system's PATH.

Usage

Go MySQL Driver is an implementation of Go's database/sql/driver interface. You only need to import the driver and can use the full database/sql API then.

Use mysql as driverName and a valid DSN as dataSourceName:

import (
	"database/sql"
	"time"

	_ "github.com/go-sql-driver/mysql"
)

// ...

db, err := sql.Open("mysql", "user:password@/dbname")
if err != nil {
	panic(err)
}
// See "Important settings" section.
db.SetConnMaxLifetime(time.Minute * 3)
db.SetMaxOpenConns(10)
db.SetMaxIdleConns(10)

Examples are available in our Wiki.

Important settings

db.SetConnMaxLifetime() is required to ensure connections are closed by the driver safely before connection is closed by MySQL server, OS, or other middlewares. Since some middlewares close idle connections by 5 minutes, we recommend timeout shorter than 5 minutes. This setting helps load balancing and changing system variables too.

db.SetMaxOpenConns() is highly recommended to limit the number of connection used by the application. There is no recommended limit number because it depends on application and MySQL server.

db.SetMaxIdleConns() is recommended to be set same to db.SetMaxOpenConns(). When it is smaller than SetMaxOpenConns(), connections can be opened and closed much more frequently than you expect. Idle connections can be closed by the db.SetConnMaxLifetime(). If you want to close idle connections more rapidly, you can use db.SetConnMaxIdleTime() since Go 1.15.

DSN (Data Source Name)

The Data Source Name has a common format, like e.g. PEAR DB uses it, but without type-prefix (optional parts marked by squared brackets):

[username[:password]@][protocol[(address)]]/dbname[?param1=value1&...&paramN=valueN]

A DSN in its fullest form:

username:password@protocol(address)/dbname?param=value

Except for the databasename, all values are optional. So the minimal DSN is:

/dbname

If you do not want to preselect a database, leave dbname empty:

/

This has the same effect as an empty DSN string:

dbname is escaped by PathEscape() since v1.8.0. If your database name is dbname/withslash, it becomes:

/dbname%2Fwithslash

Alternatively, Config.FormatDSN can be used to create a DSN string by filling a struct.

Password

Passwords can consist of any character. Escaping is not necessary.

Protocol

See net.Dial for more information which networks are available. In general you should use a Unix domain socket if available and TCP otherwise for best performance.

Address

For TCP and UDP networks, addresses have the form host[:port]. If port is omitted, the default port will be used. If host is a literal IPv6 address, it must be enclosed in square brackets. The functions net.JoinHostPort and net.SplitHostPort manipulate addresses in this form.

For Unix domain sockets the address is the absolute path to the MySQL-Server-socket, e.g. /var/run/mysqld/mysqld.sock or /tmp/mysql.sock.

Parameters

Parameters are case-sensitive!

Notice that any of true, TRUE, True or 1 is accepted to stand for a true boolean value. Not surprisingly, false can be specified as any of: false, FALSE, False or 0.

allowAllFiles

Type:           bool
Valid Values:   true, false
Default:        false

allowAllFiles=true disables the file allowlist for LOAD DATA LOCAL INFILE and allows all files. Might be insecure!

allowCleartextPasswords

Type:           bool
Valid Values:   true, false
Default:        false

allowCleartextPasswords=true allows using the cleartext client side plugin if required by an account, such as one defined with the PAM authentication plugin. Sending passwords in clear text may be a security problem in some configurations. To avoid problems if there is any possibility that the password would be intercepted, clients should connect to MySQL Server using a method that protects the password. Possibilities include TLS / SSL, IPsec, or a private network.

allowFallbackToPlaintext

Type:           bool
Valid Values:   true, false
Default:        false

allowFallbackToPlaintext=true acts like a --ssl-mode=PREFERRED MySQL client as described in Command Options for Connecting to the Server

allowNativePasswords

Type:           bool
Valid Values:   true, false
Default:        true

allowNativePasswords=false disallows the usage of MySQL native password method.

allowOldPasswords

Type:           bool
Valid Values:   true, false
Default:        false

allowOldPasswords=true allows the usage of the insecure old password method. This should be avoided, but is necessary in some cases. See also the old_passwords wiki page.

charset

Type:           string
Valid Values:   <name>
Default:        none

Sets the charset used for client-server interaction ("SET NAMES <value>"). If multiple charsets are set (separated by a comma), the following charset is used if setting the charset fails. This enables for example support for utf8mb4 (introduced in MySQL 5.5.3) with fallback to utf8 for older servers (charset=utf8mb4,utf8).

See also Unicode Support.

checkConnLiveness

Type:           bool
Valid Values:   true, false
Default:        true

On supported platforms connections retrieved from the connection pool are checked for liveness before using them. If the check fails, the respective connection is marked as bad and the query retried with another connection. checkConnLiveness=false disables this liveness check of connections.

collation

Type:           string
Valid Values:   <name>
Default:        utf8mb4_general_ci

Sets the collation used for client-server interaction on connection. In contrast to charset, collation does not issue additional queries. If the specified collation is unavailable on the target server, the connection will fail.

A list of valid charsets for a server is retrievable with SHOW COLLATION.

The default collation (utf8mb4_general_ci) is supported from MySQL 5.5. You should use an older collation (e.g. utf8_general_ci) for older MySQL.

Collations for charset "ucs2", "utf16", "utf16le", and "utf32" can not be used (ref).

See also Unicode Support.

clientFoundRows

Type:           bool
Valid Values:   true, false
Default:        false

clientFoundRows=true causes an UPDATE to return the number of matching rows instead of the number of rows changed.

columnsWithAlias

Type:           bool
Valid Values:   true, false
Default:        false

When columnsWithAlias is true, calls to sql.Rows.Columns() will return the table alias and the column name separated by a dot. For example:

SELECT u.id FROM users as u

will return u.id instead of just id if columnsWithAlias=true.

interpolateParams

Type:           bool
Valid Values:   true, false
Default:        false

If interpolateParams is true, placeholders (?) in calls to db.Query() and db.Exec() are interpolated into a single query string with given parameters. This reduces the number of roundtrips, since the driver has to prepare a statement, execute it with given parameters and close the statement again with interpolateParams=false.

This can not be used together with the multibyte encodings BIG5, CP932, GB2312, GBK or SJIS. These are rejected as they may introduce a SQL injection vulnerability!

loc

Type:           string
Valid Values:   <escaped name>
Default:        UTC

Sets the location for time.Time values (when using parseTime=true). "Local" sets the system's location. See time.LoadLocation for details.

Note that this sets the location for time.Time values but does not change MySQL's time_zone setting. For that see the time_zone system variable, which can also be set as a DSN parameter.

Please keep in mind, that param values must be url.QueryEscape'ed. Alternatively you can manually replace the / with %2F. For example US/Pacific would be loc=US%2FPacific.

timeTruncate

Type:           duration
Default:        0

Truncate time values to the specified duration. The value must be a decimal number with a unit suffix ("ms", "s", "m", "h"), such as "30s", "0.5m" or "1m30s".

maxAllowedPacket

Type:          decimal number
Default:       64*1024*1024

Max packet size allowed in bytes. The default value is 64 MiB and should be adjusted to match the server settings. maxAllowedPacket=0 can be used to automatically fetch the max_allowed_packet variable from server on every connection.

multiStatements

Type:           bool
Valid Values:   true, false
Default:        false

Allow multiple statements in one query. This can be used to bach multiple queries. Use Rows.NextResultSet() to get result of the second and subsequent queries.

When multiStatements is used, ? parameters must only be used in the first statement. interpolateParams can be used to avoid this limitation unless prepared statement is used explicitly.

It's possible to access the last inserted ID and number of affected rows for multiple statements by using sql.Conn.Raw() and the mysql.Result. For example:

conn, _ := db.Conn(ctx)
conn.Raw(func(conn any) error {
  ex := conn.(driver.Execer)
  res, err := ex.Exec(`
  UPDATE point SET x = 1 WHERE y = 2;
  UPDATE point SET x = 2 WHERE y = 3;
  `, nil)
  // Both slices have 2 elements.
  log.Print(res.(mysql.Result).AllRowsAffected())
  log.Print(res.(mysql.Result).AllLastInsertIds())
})

parseTime

Type:           bool
Valid Values:   true, false
Default:        false

parseTime=true changes the output type of DATE and DATETIME values to time.Time instead of []byte / string The date or datetime like 0000-00-00 00:00:00 is converted into zero value of time.Time.

readTimeout

Type:           duration
Default:        0

I/O read timeout. The value must be a decimal number with a unit suffix ("ms", "s", "m", "h"), such as "30s", "0.5m" or "1m30s".

rejectReadOnly

Type:           bool
Valid Values:   true, false
Default:        false

rejectReadOnly=true causes the driver to reject read-only connections. This is for a possible race condition during an automatic failover, where the mysql client gets connected to a read-only replica after the failover.

Note that this should be a fairly rare case, as an automatic failover normally happens when the primary is down, and the race condition shouldn't happen unless it comes back up online as soon as the failover is kicked off. On the other hand, when this happens, a MySQL application can get stuck on a read-only connection until restarted. It is however fairly easy to reproduce, for example, using a manual failover on AWS Aurora's MySQL-compatible cluster.

If you are not relying on read-only transactions to reject writes that aren't supposed to happen, setting this on some MySQL providers (such as AWS Aurora) is safer for failovers.

Note that ERROR 1290 can be returned for a read-only server and this option will cause a retry for that error. However the same error number is used for some other cases. You should ensure your application will never cause an ERROR 1290 except for read-only mode when enabling this option.

serverPubKey

Type:           string
Valid Values:   <name>
Default:        none

Server public keys can be registered with mysql.RegisterServerPubKey, which can then be used by the assigned name in the DSN. Public keys are used to transmit encrypted data, e.g. for authentication. If the server's public key is known, it should be set manually to avoid expensive and potentially insecure transmissions of the public key from the server to the client each time it is required.

timeout

Type:           duration
Default:        OS default

Timeout for establishing connections, aka dial timeout. The value must be a decimal number with a unit suffix ("ms", "s", "m", "h"), such as "30s", "0.5m" or "1m30s".

tls

Type:           bool / string
Valid Values:   true, false, skip-verify, preferred, <name>
Default:        false

tls=true enables TLS / SSL encrypted connection to the server. Use skip-verify if you want to use a self-signed or invalid certificate (server side) or use preferred to use TLS only when advertised by the server. This is similar to skip-verify, but additionally allows a fallback to a connection which is not encrypted. Neither skip-verify nor preferred add any reliable security. You can use a custom TLS config after registering it with mysql.RegisterTLSConfig.

writeTimeout

Type:           duration
Default:        0

I/O write timeout. The value must be a decimal number with a unit suffix ("ms", "s", "m", "h"), such as "30s", "0.5m" or "1m30s".

connectionAttributes

Type:           comma-delimited string of user-defined "key:value" pairs
Valid Values:   (<name1>:<value1>,<name2>:<value2>,...)
Default:        none

Connection attributes are key-value pairs that application programs can pass to the server at connect time.

System Variables

Any other parameters are interpreted as system variables:

• <boolean_var>=<value>: SET <boolean_var>=<value>
• <enum_var>=<value>: SET <enum_var>=<value>
• <string_var>=%27<value>%27: SET <string_var>='<value>'

Rules:

• The values for string variables must be quoted with '.
• The values must also be url.QueryEscape'ed! (which implies values of string variables must be wrapped with %27).

Examples:

• autocommit=1: SET autocommit=1
• time_zone=%27Europe%2FParis%27: SET time_zone='Europe/Paris'
• transaction_isolation=%27REPEATABLE-READ%27: SET transaction_isolation='REPEATABLE-READ'

Examples

user@unix(/path/to/socket)/dbname

root:pw@unix(/tmp/mysql.sock)/myDatabase?loc=Local

user:password@tcp(localhost:5555)/dbname?tls=skip-verify&autocommit=true

Treat warnings as errors by setting the system variable sql_mode:

user:password@/dbname?sql_mode=TRADITIONAL

TCP via IPv6:

user:password@tcp([de:ad:be:ef::ca:fe]:80)/dbname?timeout=90s&collation=utf8mb4_unicode_ci

TCP on a remote host, e.g. Amazon RDS:

id:password@tcp(your-amazonaws-uri.com:3306)/dbname

Google Cloud SQL on App Engine:

user:password@unix(/cloudsql/project-id:region-name:instance-name)/dbname

TCP using default port (3306) on localhost:

user:password@tcp/dbname?charset=utf8mb4,utf8&sys_var=esc%40ped

Use the default protocol (tcp) and host (localhost:3306):

user:password@/dbname

No Database preselected:

user:password@/

Connection pool and timeouts

The connection pool is managed by Go's database/sql package. For details on how to configure the size of the pool and how long connections stay in the pool see *DB.SetMaxOpenConns, *DB.SetMaxIdleConns, and *DB.SetConnMaxLifetime in the database/sql documentation. The read, write, and dial timeouts for each individual connection are configured with the DSN parameters readTimeout, writeTimeout, and timeout, respectively.

ColumnType Support

This driver supports the ColumnType interface introduced in Go 1.8, with the exception of ColumnType.Length(), which is currently not supported. All Unsigned database type names will be returned UNSIGNED with INT, TINYINT, SMALLINT, MEDIUMINT, BIGINT.

context.Context Support

Go 1.8 added database/sql support for context.Context. This driver supports query timeouts and cancellation via contexts. See context support in the database/sql package for more details.

[!IMPORTANT] The QueryContext, ExecContext, etc. variants provided by database/sql will cause the connection to be closed if the provided context is cancelled or timed out before the result is received by the driver.

LOAD DATA LOCAL INFILE support

For this feature you need direct access to the package. Therefore you must change the import path (no _):

import "github.com/go-sql-driver/mysql"

Files must be explicitly allowed by registering them with mysql.RegisterLocalFile(filepath) (recommended) or the allowlist check must be deactivated by using the DSN parameter allowAllFiles=true (Might be insecure!).

To use a io.Reader a handler function must be registered with mysql.RegisterReaderHandler(name, handler) which returns a io.Reader or io.ReadCloser. The Reader is available with the filepath Reader::<name> then. Choose different names for different handlers and DeregisterReaderHandler when you don't need it anymore.

See the godoc of Go-MySQL-Driver for details.

time.Time support

The default internal output type of MySQL DATE and DATETIME values is []byte which allows you to scan the value into a []byte, string or sql.RawBytes variable in your program.

However, many want to scan MySQL DATE and DATETIME values into time.Time variables, which is the logical equivalent in Go to DATE and DATETIME in MySQL. You can do that by changing the internal output type from []byte to time.Time with the DSN parameter parseTime=true. You can set the default time.Time location with the loc DSN parameter.

Caution: As of Go 1.1, this makes time.Time the only variable type you can scan DATE and DATETIME values into. This breaks for example sql.RawBytes support.

Unicode support

Since version 1.5 Go-MySQL-Driver automatically uses the collation utf8mb4_general_ci by default.

Other charsets / collations can be set using the charset or collation DSN parameter.

• When only the charset is specified, the SET NAMES <charset> query is sent and the server's default collation is used.
• When both the charset and collation are specified, the SET NAMES <charset> COLLATE <collation> query is sent.
• When only the collation is specified, the collation is specified in the protocol handshake and the SET NAMES query is not sent. This can save one roundtrip, but note that the server may ignore the specified collation silently and use the server's default charset/collation instead.

See http://dev.mysql.com/doc/refman/8.0/en/charset-unicode.html for more details on MySQL's Unicode support.

Testing / Development

To run the driver tests you may need to adjust the configuration. See the Testing Wiki-Page for details.

Go-MySQL-Driver is not feature-complete yet. Your help is very appreciated. If you want to contribute, you can work on an open issue or review a pull request.

See the Contribution Guidelines for details.

License

Go-MySQL-Driver is licensed under the Mozilla Public License Version 2.0

Mozilla summarizes the license scope as follows:

MPL: The copyleft applies to any files containing MPLed code.

That means:

• You can use the unchanged source code both in private and commercially.
• When distributing, you must publish the source code of any changed files licensed under the MPL 2.0 under a) the MPL 2.0 itself or b) a compatible license (e.g. GPL 3.0 or Apache License 2.0).
• You needn't publish the source code of your library as long as the files licensed under the MPL 2.0 are unchanged.

Please read the MPL 2.0 FAQ if you have further questions regarding the license.

You can read the full terms here: LICENSE.