Documentation Home
MySQL 5.5 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 26.9Mb
PDF (A4) - 26.9Mb
PDF (RPM) - 25.3Mb
HTML Download (TGZ) - 6.3Mb
HTML Download (Zip) - 6.4Mb
HTML Download (RPM) - 5.4Mb
Man Pages (TGZ) - 159.2Kb
Man Pages (Zip) - 263.0Kb
Info (Gzip) - 2.6Mb
Info (Zip) - 2.6Mb
Excerpts from this Manual

MySQL 5.5 Reference Manual  /  The InnoDB Storage Engine  /  InnoDB Restrictions and Limitations

14.25 InnoDB Restrictions and Limitations

This section describes restrictions and limitations of the InnoDB storage engine.

  • You cannot create a table with a column name that matches the name of an internal InnoDB column (including DB_ROW_ID, DB_TRX_ID, and DB_ROLL_PTR. This restriction applies to use of the names in any letter case.

    mysql> CREATE TABLE t1 (c1 INT, db_row_id INT) ENGINE=INNODB;
    ERROR 1166 (42000): Incorrect column name 'db_row_id'
  • SHOW TABLE STATUS does not provide accurate statistics for InnoDB tables except for the physical size reserved by the table. The row count is only a rough estimate used in SQL optimization.

  • InnoDB does not keep an internal count of rows in a table because concurrent transactions might see different numbers of rows at the same time. Consequently, SELECT COUNT(*) statements only count rows visible to the current transaction.

    For information about how InnoDB processes SELECT COUNT(*) statements, refer to the COUNT() description in Section 12.17.1, “Aggregate (GROUP BY) Function Descriptions”.

  • Changing the page size is not a supported operation and there is no guarantee that InnoDB functions normally with a page size other than 16KB. Problems compiling or running InnoDB may occur. In particular, ROW_FORMAT=COMPRESSED in the Barracuda file format assumes that the page size is at most 16KB and uses 14-bit pointers.

  • A version of InnoDB built for one page size cannot use data files or log files from a version built for a different page size. This limitation could affect restore or downgrade operations using data from MySQL 5.6, which does support page sizes other than 16KB.

  • InnoDB does not support FULLTEXT indexes.

  • InnoDB does not support indexes on spatial data type columns.

  • For limitations associated with fast index creation, see Section 14.16.6, “Limitations of Fast Index Creation”.