MySQL :: MySQL 8.0 Reference Manual :: 17.6.3.9 Tablespace AUTOEXTEND_SIZE Configuration (original) (raw)

17.6.3.9 Tablespace AUTOEXTEND_SIZE Configuration

By default, when a file-per-table or general tablespace requires additional space, the tablespace is extended incrementally according to the following rules:

• If the tablespace is less than an extent in size, it is extended one page at a time.
• If the tablespace is greater than 1 extent but smaller than 32 extents in size, it is extended one extent at a time.
• If the tablespace is more than 32 extents in size, it is extended four extents at a time.

For information about extent size, seeSection 17.11.2, “File Space Management”.

From MySQL 8.0.23, the amount by which a file-per-table or general tablespace is extended is configurable by specifying theAUTOEXTEND_SIZE option. Configuring a larger extension size can help avoid fragmentation and facilitate ingestion of large amounts of data.

To configure the extension size for a file-per-table tablespace, specify the AUTOEXTEND_SIZE size in aCREATE TABLE orALTER TABLE statement:

CREATE TABLE t1 (c1 INT) AUTOEXTEND_SIZE = 4M;

ALTER TABLE t1 AUTOEXTEND_SIZE = 8M;

To configure the extension size for a general tablespace, specify the AUTOEXTEND_SIZE size in aCREATE TABLESPACE orALTER TABLESPACE statement:

CREATE TABLESPACE ts1 AUTOEXTEND_SIZE = 4M;

ALTER TABLESPACE ts1 AUTOEXTEND_SIZE = 8M;

Note

The AUTOEXTEND_SIZE option can also be used when creating an undo tablespace, but the extension behavior for undo tablespaces differs. For more information, seeSection 17.6.3.4, “Undo Tablespaces”.

The AUTOEXTEND_SIZE setting must be a multiple of 4M. Specifying an AUTOEXTEND_SIZE setting that is not a multiple of 4M returns an error.

The AUTOEXTEND_SIZE default setting is 0, which causes the tablespace to be extended according to the default behavior described above.

The maximum allowed AUTOEXTEND_SIZE is 4GB. The maximum tablespace size is described atSection 17.22, “InnoDB Limits”.

The minimum AUTOEXTEND_SIZE setting depends on the InnoDB page size, as shown in the following table:

The default InnoDB page size is 16K (16384 bytes). To determine the InnoDB page size for your MySQL instance, query theinnodb_page_size setting:

mysql> SELECT @@GLOBAL.innodb_page_size;
+---------------------------+
| @@GLOBAL.innodb_page_size |
+---------------------------+
|                     16384 |
+---------------------------+

When the AUTOEXTEND_SIZE setting for a tablespace is altered, the first extension that occurs afterward increases the tablespace size to a multiple of theAUTOEXTEND_SIZE setting. Subsequent extensions are of the configured size.

When a file-per-table or general tablespace is created with a non-zero AUTOEXTEND_SIZE setting, the tablespace is initialized at the specifiedAUTOEXTEND_SIZE size.

ALTER TABLESPACE cannot be used to configure the AUTOEXTEND_SIZE of a file-per-table tablespace. ALTER TABLE must be used.

For tables created in file-per-table tablespaces,SHOW CREATE TABLE shows theAUTOEXTEND_SIZE option only when it is configured to a non-zero value.

To determine the AUTOEXTEND_SIZE for anyInnoDB tablespace, query the Information SchemaINNODB_TABLESPACES table. For example:

mysql> SELECT NAME, AUTOEXTEND_SIZE FROM INFORMATION_SCHEMA.INNODB_TABLESPACES 
       WHERE NAME LIKE 'test/t1';
+---------+-----------------+
| NAME    | AUTOEXTEND_SIZE |
+---------+-----------------+
| test/t1 |         4194304 |
+---------+-----------------+

mysql> SELECT NAME, AUTOEXTEND_SIZE FROM INFORMATION_SCHEMA.INNODB_TABLESPACES 
       WHERE NAME LIKE 'ts1';
+------+-----------------+
| NAME | AUTOEXTEND_SIZE |
+------+-----------------+
| ts1  |         4194304 |
+------+-----------------+

Note

An AUTOEXTEND_SIZE of 0, which is the default setting, means that the tablespace is extended according to the default tablespace extension behavior described above.