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InnoDB 1.1 for MySQL 5.5 User's Guide
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InnoDB 1.1 for MySQL 5.5 User's Guide  /  InnoDB File-Format Management  /  Identifying the File Format in Use

4.3. Identifying the File Format in Use

After you enable a given innodb_file_format, this change applies only to newly created tables rather than existing ones. If you do create a new table, the tablespace containing the table is tagged with the earliest or simplest file format that is required for the table's features. For example, if you enable file format Barracuda, and create a new table that is not compressed and does not use ROW_FORMAT=DYNAMIC, the new tablespace that contains the table is tagged as using file format Antelope.

It is easy to identify the file format used by a given tablespace or table. The table uses the Barracuda format if the Row_format reported by SHOW CREATE TABLE or INFORMATION_SCHEMA.TABLES is one of 'Compressed' or 'Dynamic'. (The Row_format is a separate column; ignore the contents of the Create_options column, which may contain the string ROW_FORMAT.) If the table in a tablespace uses neither of those features, the file uses the format supported by prior releases of InnoDB, now called file format Antelope. Then, the Row_format is one of 'Redundant' or 'Compact'.

Internal Details

InnoDB has two different file formats (Antelope and Barracuda) and four different row formats (Redundant, Compact, Dynamic, and Compressed). The Antelope file format contains Redundant and Compact row formats. A tablespace that uses the Barracuda file format uses either the Dynamic or Compressed row format.

File and row format information is written in the tablespace flags (a 32-bit number) in the *.ibd file in the 4 bytes starting at position 54 of the file, most significant byte first (the first byte of the file is byte zero). On some systems, you can display these bytes in hexadecimal with the command od -t x1 -j 54 -N 4 tablename.ibd. If all bytes are zero, the tablespace uses the Antelope file format, which is the format used by the standard InnoDB storage engine up to MySQL 5.1.

The first 6 bits of the tablespace flags can be described this way:

  • Bit 0: Zero for Antelope and no other bits will be set. One for Barracuda, and other bits may be set.

  • Bits 1 to 4: A 4 bit number representing the compressed page size. zero = not compressed, 1 = 1k, 2 = 2k, 3 = 4k, 4 = 8k.

  • Bit 5: Same value as Bit 0, zero for Antelope, and one for Barracuda. If Bit 0 and Bit 5 are set and Bits 1 to 4 are not, the row format is Dynamic.

Until MySQL 5.6, no other bits are set in the tablespace flags. If bits 6 to 31 are not zero, the tablespace is corrupt or is not an InnoDB tablespace file.


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