Redmine

When working with redmine, one sometimes needs queries based on activity history.

Basically, current "activity" tab and the "history" section of every issue page do perform a fixed query.
It would be helpful to allow users to perform a variety of queries.

• list all activities of user john from date X to date Y
• list all activities that reopen a bug from date X to date Y
• list all activities that change assignee from date X to date Y
• list all activities that change custom field F with previous value V, from date X to date Y
• list all activities on bug ID=1234 where comment contains "foo"
• list all activities without a comment

Like with current activity tab, the answer is a list of activity entries, not issues, so an issue ID may appear many times.

Notice that the examples above do not involve join with issues, they query only on fields of activity entries themselves.