InnoDB Temporary Tablespaces
MariaDB starting with 10.2
The use of the temporary tablespaces in InnoDB was introduced in MariaDB 10.2. In earlier versions, temporary tablespaces exist as part of the InnoDB system tablespace or were file-per-table depending on the configuration of the innodb_file_per_table system variable.
When the user creates a temporary table using the CREATE TEMPORARY TABLE statement and the engine is set as InnoDB, MariaDB creates a temporary tablespace file. When the table is not compressed, MariaDB writes to a shared temporary tablespace as defined by the innodb_temp_data_file_path system variable. MariaDB does not allow the creation of ROW_FORMAT=COMPRESSED temporary tables. All temporary tables will be uncompressed. MariaDB deletes temporary tablespaces when the server shuts down gracefully and is recreated when it starts again. It cannot be placed on a raw device.
Internal temporary tablespaces, (that is, temporary tables that cannot be kept in memory) use either Aria or MyISAM, depending on the aria_used_for_temp_tables system variable. You can set the default storage engine for user-created temporary tables using the default_tmp_storage_engine system variable.
Sizing Temporary Tablespaces
In order to size temporary tablespaces, use the innodb_temp_data_file_path system variable. This system variable can be specified as a command-line argument to mysqld or it can be specified in a relevant server option group in an option file. For example:
[mariadb] ... innodb_temp_data_file_path=ibtmp1:32M:autoextend
This system variable's syntax is the same as the innodb_data_file_path system variable. That is, a file name, size and option. By default, it writes a 12MB autoextending file to
ibtmp1 in the data directory.
To increase the size of the temporary tablespace, you can add a path to an additional tablespace file to the value of the the innodb_temp_data_file_path system variable. Providing additional paths allows you to spread the temporary tablespace between multiple tablespace files. The last file can have the
autoextend attribute, which ensures that you won't run out of space. For example:
[mariadb] ... innodb_temp_data_file_path=ibtmp1:32M;ibtmp2:32M:autoextend
Unlike normal tablespaces, temporary tablespaces are deleted when you stop MariaDB. To shrink temporary tablespaces to their minimum sizes, restart the server.