13.1.8 ALTER TABLESPACE Syntax

ALTER TABLESPACE tablespace_name
    {ADD|DROP} DATAFILE 'file_name'
    [INITIAL_SIZE [=] size]
    [WAIT]
    ENGINE [=] engine_name

This statement can be used either to add a new data file, or to drop a data file from a tablespace.

The ADD DATAFILE variant enables you to specify an initial size using an INITIAL_SIZE clause, where size is measured in bytes; the default value is 128M (128 megabytes). You may optionally follow this integer value with a one-letter abbreviation for an order of magnitude, similar to those used in my.cnf. Generally, this is one of the letters M (for megabytes) or G (for gigabytes).

Note

All MySQL Cluster Disk Data objects share the same namespace. This means that each Disk Data object must be uniquely named (and not merely each Disk Data object of a given type). For example, you cannot have a tablespace and an data file with the same name, or an undo log file and a with the same name.

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file names for data files could not be longer than 128 characters. (Bug #31770)

On 32-bit systems, the maximum supported value for INITIAL_SIZE is 4G. (Bug #29186)

INITIAL_SIZE is rounded as for CREATE TABLESPACE. Beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.32, MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB 7.1.2, this rounding is done explicitly (also as with CREATE TABLESPACE).

Once a data file has been created, its size cannot be changed; however, you can add more data files to the tablespace using additional ALTER TABLESPACE ... ADD DATAFILE statements.

Using DROP DATAFILE with ALTER TABLESPACE drops the data file 'file_name' from the tablespace. You cannot drop a data file from a tablespace which is in use by any table; in other words, the data file must be empty (no extents used). See Section 17.5.12.1, “MySQL Cluster Disk Data Objects”. In addition, any data file to be dropped must previously have been added to the tablespace with CREATE TABLESPACE or ALTER TABLESPACE.

Both ALTER TABLESPACE ... ADD DATAFILE and ALTER TABLESPACE ... DROP DATAFILE require an ENGINE clause which specifies the storage engine used by the tablespace. In MySQL 5.1, the only accepted values for engine_name are NDB and NDBCLUSTER.

WAIT is parsed but otherwise ignored, and so has no effect in MySQL 5.1. It is intended for future expansion.

When ALTER TABLESPACE ... ADD DATAFILE is used with ENGINE = NDB, a data file is created on each Cluster data node. You can verify that the data files were created and obtain information about them by querying the INFORMATION_SCHEMA.FILES table. For example, the following query shows all data files belonging to the tablespace named newts:

mysql> SELECT LOGFILE_GROUP_NAME, FILE_NAME, EXTRA
    -> FROM INFORMATION_SCHEMA.FILES
    -> WHERE TABLESPACE_NAME = 'newts' AND FILE_TYPE = 'DATAFILE';
+--------------------+--------------+----------------+
| LOGFILE_GROUP_NAME | FILE_NAME    | EXTRA          |
+--------------------+--------------+----------------+
| lg_3               | newdata.dat  | CLUSTER_NODE=3 |
| lg_3               | newdata.dat  | CLUSTER_NODE=4 |
| lg_3               | newdata2.dat | CLUSTER_NODE=3 |
| lg_3               | newdata2.dat | CLUSTER_NODE=4 |
+--------------------+--------------+----------------+
2 rows in set (0.03 sec)

See Section 20.26.1, “The INFORMATION_SCHEMA FILES Table”.

ALTER TABLESPACE was added in MySQL 5.1.6. In MySQL 5.1, it is useful only with Disk Data storage for MySQL Cluster. See Section 17.5.12, “MySQL Cluster Disk Data Tables”.