Steps to reproduce the issue

We have about 2 million action log entries and roughly 400k users.
When trying to view the action log then the every page/action in the action log viewer takes >20 seconds to load.

Expected result

As there are only 20 entries visible in the action log grid I would expect it to be quick to show.

Actual result

Take 20-30 secons to show the default screen

System information (as much as possible)

I noticed whenever I try to do any action in the action log viewer the following query is executed:

SELECT u.id AS value,u.username AS text
FROM jos_users AS u
INNER JOIN jos_action_logs AS c ON c.user_id = u.id
GROUP BY u.id,u.username
ORDER BY u.username

Not sure why this generalized query is run at all.

Additional comments

Query seems to originate from LogcreatorField->getOptions()
I think that is an extremly costly/inefficient query and it is only used to populate the user field in the filter - instead that field should be a plain text search field.