As InnoDB evolves, new on-disk data structures are sometimes
required to support new features. This release of InnoDB
introduces two such new data structures: compressed tables (see
Chapter 3, InnoDB Data Compression), and long variable-length
columns stored off-page (see Chapter 5,
InnoDB Row Storage and Row Formats).
These features both require use of the new
Barracuda file format.
These new data structures are not compatible with prior versions of InnoDB. The other new features of the InnoDB Plugin are compatible with the original Antelope file format and do not require the Barracuda file format.
In general, a newer version of InnoDB may create a table or index that cannot safely be read or written with a prior version of InnoDB without risk of crashes, hangs, wrong results or corruptions. The InnoDB Plugin introduces a new mechanism to guard against these conditions, and to help preserve compatibility among database files and versions of InnoDB. This mechanism lets you take advantage of some new features of an InnoDB release (e.g., performance improvements and bug fixes), and still preserve the option of using your database with a prior version of InnoDB, by precluding the use of new features that create downward incompatible on-disk data structures.