8.12. mysqldump — A Database Backup Program

MySQL 5.0

8.12. mysqldump — A Database Backup Program

The mysqldump client is a backup program originally written by Igor Romanenko. It can be used to dump a database or a collection of databases for backup or for transferring the data to another SQL server (not necessarily a MySQL server). The dump contains SQL statements to create the table or populate it, or both.

If you are doing a backup on the server, and your tables all are tables, consider using the mysqlhotcopy instead because it can accomplish faster backups and faster restores. See Section 8.13, “mysqlhotcopy — A Database Backup Program”.

There are three general ways to invoke mysqldump:

shell> ]  []
shell> ] --databases  [ ...]
shell> ] --all-databases

If you do not name any tables following or if you use the or option, entire databases are dumped.

To get a list of the options your version of mysqldump supports, execute mysqldump --help.

If you run mysqldump without the or option, mysqldump loads the whole result set into memory before dumping the result. This can be a problem if you are dumping a big database. The option is enabled by default, but can be disabled with .

If you are using a recent copy of the mysqldump program to generate a dump to be reloaded into a very old MySQL server, you should not use the or option. Use instead.

mysqldump supports the following options:

  • ,

    Display a help message and exit.

  • Add a statement before each statement.

  • Add a statement before each statement.

  • Surround each table dump with and statements. This results in faster inserts when the dump file is reloaded. See Section 7.2.16, “Speed of Statements”.

  • ,

    Dump all tables in all databases. This is the same as using the option and naming all the databases on the command line.

  • Allow creation of column names that are keywords. This works by prefixing each column name with the table name.

  • The directory where character sets are installed. See Section 5.11.1, “The Character Set Used for Data and Sorting”.

  • ,

    Write additional information in the dump file such as program version, server version, and host. . This option is enabled by default. To suppress additional, use .

  • Produce less verbose output. This option suppresses comments and enables the , , , and options.

  • Produce output that is more compatible with other database systems or with older MySQL servers. The value of can be , , , , , , , , , , or . To use several values, separate them by commas. These values have the same meaning as the corresponding options for setting the server SQL mode. See Section 5.2.5, “The Server SQL Mode”.

    This option does not guarantee compatibility with other servers. It only enables those SQL mode values that are currently available for making dump output more compatible. For example, does not map data types to Oracle types or use Oracle comment syntax.

  • ,

    Use complete statements that include column names.

  • ,

    Compress all information sent between the client and the server if both support compression.

  • Include all MySQL-specific table options in the statements.

  • ,

    Dump several databases. Normally, mysqldump treats the first name argument on the command line as a database name and following names as table names. With this option, it treats all name arguments as database names. and statements are included in the output before each new database.

  • ], ]

    Write a debugging log. The string is often '. The default is .

  • Use as the default character set. See Section 5.11.1, “The Character Set Used for Data and Sorting”. If not specified, mysqldump uses .

  • Write statements rather than statements.

  • On a master replication server, delete the binary logs after performing the dump operation. This option automatically enables .

  • ,

    For each table, surround the statements with DISABLE KEYS */; and ENABLE KEYS */; statements. This makes loading the dump file faster because the indexes are created after all rows are inserted. This option is effective for tables only.

  • ,

    Use multiple-row syntax that include several lists. This results in a smaller dump file and speeds up inserts when the file is reloaded.

  • , , , ,

    These options are used with the option and have the same meaning as the corresponding clauses for . See Section 13.2.5, “ Syntax”.

  • ,

    Deprecated. Now renamed to .

  • ,

    Flush the MySQL server log files before starting the dump. This option requires the privilege. Note that if you use this option in combination with the (or ) option, the logs are flushed for each database dumped. The exception is when using or : In this case, the logs are flushed only once, corresponding to the moment that all tables are locked. If you want your dump and the log flush to happen at exactly the same moment, you should use together with either or .

  • ,

    Continue even if an SQL error occurs during a table dump.

    One use for this option is to cause mysqldump to continue executing even when it encounters a view that has become invalid because the defintion refers to a table that has been dropped. Without , mysqldump exits with an error message. With , mysqldump prints the error message, but it also writes a SQL comment containing the view definition to the dump output and continues executing.

  • ,

    Dump data from the MySQL server on the given host. The default host is .

  • Dump binary columns using hexadecimal notation (for example, becomes ). The affected data types are , , and . As of MySQL 5.0.13, columns are affected as well.

  • Do not dump the given table, which must be specified using both the database and table names. To ignore multiple tables, use this option multiple times.

  • Write statements with the option.

  • ,

    Lock all tables across all databases. This is achieved by acquiring a global read lock for the duration of the whole dump. This option automatically turns off and .

  • ,

    Lock all tables before starting the dump. The tables are locked with to allow concurrent inserts in the case of tables. For transactional tables such as and , is a much better option, because it does not need to lock the tables at all.

    Please note that when dumping multiple databases, locks tables for each database separately. So, this option does not guarantee that the tables in the dump file are logically consistent between databases. Tables in different databases may be dumped in completely different states.

  • ]

    Write the binary log filename and position to the output. This option requires the privilege and the binary log must be enabled. If the option value is equal to 1, the position and filename are written to the dump output in the form of a statement that makes a slave server start from the correct position in the master's binary logs if you use this SQL dump of the master to set up a slave. If the option value is equal to 2, the statement is written as an SQL comment. This is the default action if is omitted.

    The option turns on , unless also is specified (in which case, a global read lock is only acquired a short time at the beginning of the dump. See also the description for . In all cases, any action on logs happens at the exact moment of the dump. This option automatically turns off .

  • Enclose the statements for each dumped table within and statements.

  • ,

    This option suppresses the statements that are otherwise included in the output if the or option is given.

  • ,

    Do not write statements that re-create each dumped table.

  • ,

    Do not write any row information for the table. This is very useful if you want to dump only the statement for the table.

  • This option is shorthand; it is the same as specifying . It should give you a fast dump operation and produce a dump file that can be reloaded into a MySQL server quickly.

    The option is enabled by default. To disable the options that it enables, use . To disable only certain of the options enabled by , use their forms; for example, or . Alternatively, use to disable the options enabled by , followed by options to enable the features that you want. Options are processed in order, so the options to enable features must follow . For example, enables extended inserts, but does not.

  • Sorts each table's rows by its primary key, or its first unique index, if such an index exists. This is useful when dumping a table to be loaded into an table, but will make the dump itself take considerably longer.

  • ], ]

    The password to use when connecting to the server. If you use the short option form (), you cannot have a space between the option and the password. If you omit the value following the or option on the command line, you are prompted for one.

    Specifying a password on the command line should be considered insecure. See Section 5.9.6, “Keeping Your Password Secure”.

  • ,

    The TCP/IP port number to use for the connection.

  • The connection protocol to use.

  • ,

    This option is useful for dumping large tables. It forces mysqldump to retrieve rows for a table from the server a row at a time rather than retrieving the entire row set and buffering it in memory before writing it out.

  • ,

    Quote database, table, and column names within ‘’ characters. If the SQL mode is enabled, names are quoted within ‘’ characters. This option is enabled by default. It can be disabled with , but this option should be given after any option such as that may enable .

  • ,

    Direct output to a given file. This option should be used on Windows to prevent newline ‘’ characters from being converted to ‘’ carriage return/newline sequences. The result file is created and its contents overwritten, even if an error occurs while generating the dump. The previous contents are lost.

  • ,

    Dump stored routines (functions and procedures) from the dumped databases. The output generated by using contains and statements to re-create the routines. However, these statements do not include attributes such as the routine creation and modification timestamps. This means that when the routines are reloaded, they will be created with the timestamps equal to the reload time.

    If you require routines to be re-created with their original timestamp attributes, do not use . Instead, dump and reload the contents of the table directly, using a MySQL account that has appropriate privileges for the database.

    This option was added in MySQL 5.0.13. Before that, stored routines are not dumped. Routine values are not dumped until MySQL 5.0.20. This means that before 5.0.20, when routines are reloaded, they will be created with the definer set to the reloading user. If you require routines to be re-created with their original definer, dump and load the contents of the table directly as described earlier.

  • Add to the output. This option is enabled by default. To suppress the statement, use .

  • This option issues a SQL statement before dumping data from the server. It is useful only with transactional tables such as and , because then it dumps the consistent state of the database at the time when was issued without blocking any applications.

    When using this option, you should keep in mind that only tables are dumped in a consistent state. For example, any or tables dumped while using this option may still change state.

    The option and the option are mutually exclusive, because causes any pending transactions to be committed implicitly.

    This option is not supported for MySQL Cluster tables; the results cannot be guaranteed to be consistent due to the fact that the storage engine supports only the transaction isolation level. You should always use backup and restore instead.

    To dump big tables, you should combine this option with .

  • See the description for the option.

  • ,

    For connections to , the Unix socket file to use, or, on Windows, the name of the named pipe to use.

  • See the description for the option.

  • Options that begin with specify whether to connect to the server via SSL and indicate where to find SSL keys and certificates. See Section 5.9.7.3, “SSL Command Options”.

  • ,

    Produce tab-separated data files. For each dumped table, mysqldump creates a .sql file that contains the statement that creates the table, and a .txt file that contains its data. The option value is the directory in which to write the files.

    By default, the data files are formatted using tab characters between column values and a newline at the end of each line. The format can be specified explicitly using the and options.

    Note: This option should be used only when mysqldump is run on the same machine as the mysqld server. You must have the privilege, and the server must have permission to write files in the directory that you specify.

  • Override the or option. All name arguments following the option are regarded as table names.

  • Dump triggers for each dumped table. This option is enabled by default; disable it with . This option was added in MySQL 5.0.11. Before that, triggers are not dumped.

  • Add to the dump file so that columns can be dumped and reloaded between servers in different time zones. Without this option, columns are dumped and reloaded in the time zones local to the source and destination servers, which can cause the values to change. also protects against changes due to daylight saving time. is enabled by default. To disable it, use . This option was added in MySQL 5.0.15.

  • ,

    The MySQL username to use when connecting to the server.

  • ,

    Verbose mode. Print more information about what the program does.

  • ,

    Display version information and exit.

  • ', '

    Dump only rows selected by the given condition. Note that quotes around the condition are mandatory if it contains spaces or other characters that are special to your command interpreter.

    Examples:

    --where="user='jimf'"
    -w"userid>1"
    -w"userid<1"
    
  • ,

    Write dump output as well-formed XML.

You can also set the following variables by using = syntax:

  • The maximum size of the buffer for client/server communication. The maximum is 1GB.

  • The initial size of the buffer for client/server communication. When creating multiple-row-insert statements (as with option or ), mysqldump creates rows up to length. If you increase this variable, you should also ensure that the variable in the MySQL server is at least this large.

It is also possible to set variables by using = or = syntax. This syntax is deprecated.

The most common use of mysqldump is probably for making a backup of an entire database:

shell>  > 

You can read the dump file back into the server like this:

shell>  < 

Or like this:

shell> " 

mysqldump is also very useful for populating databases by copying data from one MySQL server to another:

shell>  | mysql --host= -C 

It is possible to dump several databases with one command:

shell>  [ ...] > my_databases.sql

To dump all databases, use the option:

shell> 

For tables, provides a way of making an online backup:

shell> 

This backup just needs to acquire a global read lock on all tables (using ) at the beginning of the dump. As soon as this lock has been acquired, the binary log coordinates are read and the lock is released. If and only if one long updating statement is running when the statement is issued, the MySQL server may get stalled until that long statement finishes, and then the dump becomes lock-free. If the update statements that the MySQL server receives are short (in terms of execution time), the initial lock period should not be noticeable, even with many updates.

For point-in-time recovery (also known as “roll-forward,” when you need to restore an old backup and replay the changes that happened since that backup), it is often useful to rotate the binary log (see Section 5.12.3, “The Binary Log”) or at least know the binary log coordinates to which the dump corresponds:

shell> 

Or:

shell> 
              

The simultaneous use of and provides a convenient way to make an online backup suitable for point-in-time recovery if tables are stored in the storage engine.

For more information on making backups, see Section 5.10.1, “Database Backups”, and Section 5.10.2, “Example Backup and Recovery Strategy”.