Comment 2 for bug 668138

Actually, it might be triggered by 8.4. The following query performs well enough:

SELECT BugTask.*, Product.*, SourcePackageName.*, Bug.*
FROM BugTask
JOIN Bug ON BugTask.bug = Bug.id
LEFT JOIN Product ON BugTask.product = Product.id
LEFT JOIN SourcePackageName ON BugTask.sourcepackagename = SourcePackageName.id WHERE
    BugTask.status IN (10, 15, 20, 21, 22, 25)
    AND Bug.duplicateof is NULL
    AND Bug.private IS FALSE
    AND BugTask.id IN (
        SELECT DISTINCT BugTask.id
        FROM BugTask, BugMessage, Message
        WHERE
            Message.owner = 293289
            AND Message.id = BugMessage.message
            AND BugTask.bug = BugMessage.bug
            AND Message.id NOT IN (
                SELECT BugMessage.message FROM BugMessage
                WHERE BugMessage.bug = BugTask.bug
                ORDER BY BugMessage.id LIMIT 1 ) )
ORDER BY BugTask.importance DESC, BugTask.id LIMIT 76 OFFSET 0;

The differences here:

  - Use a normal join for Bug rather than a left outer join.
  - Add DISTINCT to the first IN subselect. Ideally the query planner would do this for us in cases where it helps and not hinders.