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MySQL 5.7 Reference Manual  /  ...  /  COMPACT and REDUNDANT Row Formats

15.11.4 COMPACT and REDUNDANT Row Formats

Early versions of InnoDB used an unnamed file format (now called Antelope) for database files. The Antelope file format supports the COMPACT or REDUNDANT row formats. With these row formats, InnoDB stores up to the first 768 bytes of variable-length columns (such as BLOB and VARCHAR) in the index record within the B-tree node, with the remainder stored on the overflow pages.

To preserve compatibility with earlier versions of InnoDB, COMPACT remained the default row format up to MySQL 5.7.8. As of MySQL 5.7.9, the default row format is DYNAMIC, which is defined by the innodb_default_row_format configuration option. See Section 15.11.3, “DYNAMIC and COMPRESSED Row Formats” for information about the DYNAMIC and COMPRESSED row formats.

With the Antelope file format, if the value of a column is 768 bytes or less, no overflow page is needed, and some savings in I/O may result, since the value is in the B-tree node. This works well for relatively short BLOBs, but may cause B-tree nodes to fill with data rather than key values, reducing their efficiency. Tables with many BLOB columns could cause B-tree nodes to become too full of data, and contain too few rows, making the entire index less efficient than if the rows were shorter or if the column values were stored off-page.

For information about the physical row structure of tables that use the REDUNDANT or COMPACT row format, see Section 15.8.3, “Physical Row Structure of InnoDB Tables”.

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