A followup on show_compatibility_56

Giuseppe and Shlomi both blogged on one of the recent changes introduced to MySQL 5.7.8-rc, where the setting show_compatibility_56 is now set OFF by default.

Both raise very good points. Here is how we plan to address them:

  1. The permissions issue reported by Giuseppe will be fixed.
  2. When selecting from information_schema tables in show_compatibility_56=OFF mode, an error will now be produced:

    mysql> select * from information_schema.global_variables;
    ERROR 3167 (HY000): The 'INFORMATION_SCHEMA.GLOBAL_VARIABLES' feature is disabled; see the documentation for 'show_compatibility_56'

    (Previously this was a warning + empty set returned)
  3. When show_compatibility_56=ON, users will now be able to select from either information_schema or performance_schema tables. This presents a more viable upgrade path for users that need some period to transition.

The show_compatibility_56 setting itself will remain deprecated, as it was from its introduction. This signifies that we intend to remove INFORMATION_SCHEMA.GLOBAL_VARIABLES in a future release.

Outside of the scope of today’s update, my colleague Mark Leith has also volunteered to blog with examples of how the new performance_schema tables now expose variables down to the thread-level. This will add more context as to why we are moving this meta data from information_schema to performance_schema. Thanks Mark!

So thank you again to Giuseppe and Shlomi for helping make a better MySQL. We’re delighted to incorporate your feedback!

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I joined MySQL AB in 2006, left, and am now back at Oracle working on the MySQL team. I’ve also worked at Percona and InPowered.