Restoring Individual Tables¶
In server versions prior to 5.6, it is not possible to copy tables between
servers by copying the files, even with innodb_file_per_table. However,
with the Percona XtraBackup, you can export individual tables from any
InnoDB database, and import them into Percona Server with XtraDB or
MySQL 5.6 (The source doesn’t have to be XtraDB or or MySQL 5.6, but the
destination does). This only works on individual .ibd files, and cannot
export a table that is not contained in its own .ibd file.
Note
If you’re running Percona Server version older than 5.5.10-20.1, variable innodb_expand_import should be used instead of innodb_import_table_from_xtrabackup.
Exporting tables¶
Exporting is done in the preparation stage, not at the moment of creating the
backup. Once a full backup is created, prepare it with the
innobackupex --export option:
$ innobackupex --apply-log --export /path/to/backup
This will create for each InnoDB with its own tablespace a file with
.exp extension. An output of this procedure would contain:
..
xtrabackup: export option is specified.
xtrabackup: export metadata of table 'mydatabase/mytable' to file
`./mydatabase/mytable.exp` (1 indexes)
..
Now you should see a .exp file in the target directory:
$ find /data/backups/mysql/ -name export_test.*
The result should be similar to the following:
/data/backups/mysql/test/export_test.exp
/data/backups/mysql/test/export_test.ibd
/data/backups/mysql/test/export_test.cfg
These three files are all you need to import the table into a server running Percona Server for MySQL with XtraDB or MySQL 5.6.
Note
MySQL uses .cfg file which contains InnoDB dictionary dump in special format. This format is different from the .exp one which is used in XtraDB for the same purpose. Strictly speaking, a .cfg file is not required to import a tablespace to MySQL 5.6 or Percona Server for MySQL 5.6. A tablespace will be imported successfully even if it is from another server, but InnoDB will do schema validation if the corresponding .cfg file is present in the same directory.
Each .exp (or .cfg) file will be used for importing that table.
Note
InnoDB does a slow shutdown (i.e. full purge + change buffer merge) on –export, otherwise the tablespaces wouldn’t be consistent and thus couldn’t be imported. All the usual performance considerations apply: sufficient buffer pool (i.e. --use-memory, 100MB by default) and fast enough storage, otherwise it can take a prohibitive amount of time for export to complete.
Importing tables¶
To import a table to other server, first create a new table with the same structure as the one that will be imported at that server:
OTHERSERVER|mysql> CREATE TABLE mytable (...) ENGINE=InnoDB;
then discard its tablespace:
OTHERSERVER|mysql> ALTER TABLE mydatabase.mytable DISCARD TABLESPACE;
Next, copy mytable.ibd and mytable.exp ( or mytable.cfg
if importing to MySQL 5.6) files to database’s home, and import its
tablespace:
OTHERSERVER|mysql> ALTER TABLE mydatabase.mytable IMPORT TABLESPACE;
Set the owner and group of the files:
$ chown -R mysql:mysql /datadir/db_name/table_name.*
After running this command, data in the imported table will be available.