Bug #69519 InnoDB data dictionary LRU sizing through table_definition_cache is undocumented
Submitted: 20 Jun 2013 4:20 Modified: 1 Jul 2013 7:43
Reporter: Laurynas Biveinis Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version:5.6 OS:Any
Assigned to: Bugs System CPU Architecture:Any
Tags: data dictionary, table_definition_cache

[20 Jun 2013 4:20] Laurynas Biveinis
Description:
According to [1], InnoDB in 5.6 has a new feature where the data dictionary is organized as LRU with a length limit, which is governed by table_definition_cache setting.  But [2] does not document this, it only mentions the FRM cache.

[1] https://blogs.oracle.com/mysqlinnodb/entry/mysql_5_6_data_dictionary
[2] https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_table_definiti...

How to repeat:
Docs reading

Suggested fix:
Add text to [2] stating that table_definition_cache is used as a soft InnoDB data dictionary LRU length limit. If the limitations mentioned in [1] still exist (i.e. cannot evict tables in a FK relationship), then they should be documented too.
[20 Jun 2013 10:34] MySQL Verification Team
Hello Laurynas,

Thank you for the report.

Thanks,
Umesh
[28 Jun 2013 18:20] Bugs System
The information for table_definition_cache has been revised. The revised content will appear soon, in the next published documentation build. 

http://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_table_definitio...
http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_table_definitio...

Thank you for the bug report.
[1 Jul 2013 7:43] Laurynas Biveinis
Thanks Daniel.

5.6 docs are pushed and I see extra quotes in https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_table_definiti...:

"For InnoDB, table_definition_cache is also
...
...
are not subject to eviction." 

These quotes are not me quoting the docs but literal quotes on the page. Should these be removed?
[2 Jul 2013 11:40] Bugs System
Thanks for the catch, Laurynas. I removed the quotes this morning. The revisions will appear with the next published doc build.