Documentation Home
MySQL 5.6 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 31.1Mb
PDF (A4) - 31.1Mb
PDF (RPM) - 30.3Mb
EPUB - 7.7Mb
HTML Download (TGZ) - 7.5Mb
HTML Download (Zip) - 7.6Mb
HTML Download (RPM) - 6.5Mb
Eclipse Doc Plugin (TGZ) - 8.3Mb
Eclipse Doc Plugin (Zip) - 10.1Mb
Man Pages (TGZ) - 182.5Kb
Man Pages (Zip) - 293.8Kb
Info (Gzip) - 2.9Mb
Info (Zip) - 2.9Mb
Excerpts from this Manual

MySQL 5.6 Reference Manual  /  ...  /  Reclaiming Disk Space with TRUNCATE TABLE

14.12.5 Reclaiming Disk Space with TRUNCATE TABLE

To reclaim operating system disk space when truncating an InnoDB table, the table must be stored in its own .ibd file. For a table to be stored in its own .ibd file, innodb_file_per_table must enabled when the table is created. Additionally, there cannot be a foreign key constraint between the table being truncated and other tables, otherwise the TRUNCATE TABLE operation fails. A foreign key constraint between two columns in the same table, however, is permitted.

When a table is truncated, it is dropped and re-created in a new .ibd file, and the freed space is returned to the operating system. This is in contrast to truncating InnoDB tables that are stored within the InnoDB system tablespace (tables created when innodb_file_per_table=OFF), where only InnoDB can use the freed space after the table is truncated.

The ability to truncate tables and return disk space to the operating system also means that physical backups can be smaller. Truncating tables that are stored in the system tablespace (tables created when innodb_file_per_table=OFF) leaves blocks of unused space in the system tablespace.

User Comments
Sign Up Login You must be logged in to post a comment.