Redmine

The LEFT JOIN with an OR in its clause in the first acts_as_activity_provider call in attachment.rb can cause very long query times for large numbers of attachments (on MySQL, at least).

One example we observed was on Users#show, where the query for activity on version / project attachments took 30 seconds (and yielded zero results) for a user that authored over 100k attachments (but none of them were attached to versions or projects).

This patch that was extracted from Planio adds a `where` clause that limits the number of attachments that are at all considered for the joins to those that are actually attached to a version or project.