Description:
Back when i created my replication status INFORMATION_SCHEMA plugins ( see e.g. https://launchpad.net/is-replication-status ) i was told that these were a good idea, but should go to the soon-to-come PERFORMANCE_SCHEMA instead of INFORMATION_SCHEMA
Now about five years later we do have the 2nd major release with PERFORMANCE_SCHEMA, but there are still no P_S tables providing the equivalent of SHOW MASTER STATUS or SHOW SLAVE STATUS that would allow for selecting only specific status columns instead of getting the full STATUS result set (which can get additional columns between releases and so can't really be used e.g. with prepared statements or within stored procedures where the number of bound variables needs to be fixed), and the related worklog item seems to be inactive
And as there is no plugin interface for P_S i can't simply re-implement my existing I_S plugins to provide the same data from within P_S (as originally requested) either.
I could of course add those two tables as a hard coded patch against the server code, but that would require recompiling mysqld instead of loading a plugin into a standard mysqld binary ...
On a more general level plugins are limited to expose status tables to the INFORMATION_SCHEMA even if these tables actually contain performance related information ... like e.g. all those extra I_S tables that the InnoDB/XtraDB storage engine plugins provide ...
How to repeat:
Check documentation and/or code to see that there is a plugin interface for extending the INFORMATION_SCHEMA, but not for the PERFORMANCE_SCHEMA
Suggested fix:
Provide a plugin interface similar to the INFORMATION_SCHEMA one to allow for adding extra P_S tables dynamically
