16.2 Removal of File-based Metadata Storage

In previous MySQL releases, dictionary data was partially stored in metadata files. Issues with file-based metadata storage included expensive file scans, susceptibility to file system-related bugs, complex code for handling of replication and crash recovery failure states, and a lack of extensibility that made it difficult to add metadata for new features and relational objects.

The metadata files listed below are removed from MySQL. Unless otherwise noted, data previously stored in metadata files is now stored in data dictionary tables.

• .frm files: Table metadata files. With the removal of .frm files:

  • The 64KB table definition size limit imposed by the .frm file structure is removed.

  • The Information Schema TABLES table's VERSION column reports a hardcoded value of 10, which is the last .frm file version used in MySQL 5.7.

• .par files: Partition definition files. InnoDB stopped using partition definition files in MySQL 5.7 with the introduction of native partitioning support for InnoDB tables.

• .TRN files: Trigger namespace files.

• .TRG files: Trigger parameter files.

• .isl files: InnoDB Symbolic Link files containing the location of file-per-table tablespace files created outside of the data directory.

• db.opt files: Database configuration files. These files, one per database directory, contained database default character set attributes.

• ddl_log.log file: The file contained records of metadata operations generated by data definition statements such as DROP TABLE and ALTER TABLE.