Moving an InnoDB Database with FLUSH TABLES .. FOR EXPORT

If we wanted to move a large InnoDB database our options were very limited. Essentially we had to mysqldump the single database or move the entire tablespace. I did have an idea for moving a single InnoDB database by copying files but only ever tried it out with TokuDB. This method worked but seemed to frighten the developers so it’s something I never pursued beyond proof-of-concept.

With the FLUSH TABLES .. FOR EXPORT feature we have another option which may be more convenient in some cases. Here’s a practical example of this feature…

We’re using the sakila database and MariaDB 10.0.15 but it should also work with MySQL 5.6 onwards. Note that this procedure requires the innodb_file_per_table is on and the tables will be read-only for the duration of the export.

First we need to generate a list of tables

USE sakila
 
SET SESSION group_concat_max_len = 10240;
 
SELECT GROUP_CONCAT("`", TABLE_NAME, "`")
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = DATABASE()
AND TABLE_TYPE = 'BASE TABLE'
AND `ENGINE` = 'InnoDB';

From this output we can build the statement to export the tables…

FLUSH TABLES `actor`,`address`,`category`,`city`,`country`,`customer`,`film`,`film_actor`,`film_category`,`inventory`,`language`,`payment`,`rental`,`staff`,`store` FOR EXPORT;

Create a database on the other server you will be moving the tables to.

CREATE DATABASE sakila2;
 
USE sakila2;

Copy the structure of your database to sakila2 using your preferred method. Then execute the following queries. These will generate statements that will allow us to import the tablespaces. Save the output.

USE sakila2;
 
SELECT CONCAT("ALTER TABLE `", TABLE_NAME, "` DISCARD TABLESPACE;")
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = DATABASE()
AND TABLE_TYPE = 'BASE TABLE'
AND `ENGINE` = 'InnoDB';
 
SELECT CONCAT("ALTER TABLE `", TABLE_NAME, "` IMPORT TABLESPACE;")
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = DATABASE()
AND TABLE_TYPE = 'BASE TABLE'
AND `ENGINE` = 'InnoDB';

Discard the tablespaces on the destination server so the new ones can be imported…

SET @@session.foreign_key_checks = 0;
ALTER TABLE `actor` DISCARD TABLESPACE;
ALTER TABLE `address` DISCARD TABLESPACE;
ALTER TABLE `category` DISCARD TABLESPACE;
ALTER TABLE `city` DISCARD TABLESPACE;
ALTER TABLE `country` DISCARD TABLESPACE;
ALTER TABLE `customer` DISCARD TABLESPACE;
ALTER TABLE `film` DISCARD TABLESPACE;
ALTER TABLE `film_actor` DISCARD TABLESPACE;
ALTER TABLE `film_category` DISCARD TABLESPACE;
ALTER TABLE `inventory` DISCARD TABLESPACE;
ALTER TABLE `language` DISCARD TABLESPACE;
ALTER TABLE `payment` DISCARD TABLESPACE;
ALTER TABLE `rental` DISCARD TABLESPACE;
ALTER TABLE `staff` DISCARD TABLESPACE;
ALTER TABLE `store` DISCARD TABLESPACE;
SET @@session.foreign_key_checks = 1;

While the tables locks are still alive we need to copy all of the ibd and cfg files to the destination server. In later version of MySQL / MariaDB you don’t strictly need the cfg as the table structures can be discovered.

scp /var/lib/sakila/{actor,address,category,etc}.{ibd,cfg} user@destination-server:/var/lib/mysql/sakila2

Once the copy is complete unlock the tables at the source…

UNLOCK TABLES;

You probably need to change the ownership of the files at the destination…

chown -R mysql:mysql /var/lib/mysql/sakila2

Now we should be ready to import the tablespaces…

USE sakila2;
 
SET @@session.foreign_key_checks = 0;
ALTER TABLE `actor` IMPORT TABLESPACE;
ALTER TABLE `address` IMPORT TABLESPACE;
ALTER TABLE `category` IMPORT TABLESPACE;
ALTER TABLE `city` IMPORT TABLESPACE;
ALTER TABLE `country` IMPORT TABLESPACE;
ALTER TABLE `customer` IMPORT TABLESPACE;
ALTER TABLE `film` IMPORT TABLESPACE;
ALTER TABLE `film_actor` IMPORT TABLESPACE;
ALTER TABLE `film_category` IMPORT TABLESPACE;
ALTER TABLE `inventory` IMPORT TABLESPACE;
ALTER TABLE `language` IMPORT TABLESPACE;
ALTER TABLE `payment` IMPORT TABLESPACE;
ALTER TABLE `rental` IMPORT TABLESPACE;
ALTER TABLE `staff` IMPORT TABLESPACE;
ALTER TABLE `store` IMPORT TABLESPACE;
SET @session.foreign_key_checks = 1;

Now your exported tables should be ready for action. If you want to make sure then run some CHECK TABLE statements against your data…

SELECT CONCAT("CHECK TABLE ", TABLE_NAME, ";")
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = DATABASE()
AND TABLE_TYPE = "BASE TABLE";

UPDATE – 2014-02-20 Corrected scp command typo.
UPDATE – 2015-03-27 Table statistics will be wrong after doing this so you probably want to run ANALYZE TABLE.


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