Comment 5 for bug 497386

The following query might be somewhere to start. It uses window functions which are a new feature in PostgreSQL 8.4. They'll allow us to calculate the message index and slice on it straight in the database.

SELECT * FROM (
   SELECT message.*,
          row_number() OVER (
             ORDER BY message.datecreated, message.id) AS index
     FROM message, bugmessage
    WHERE bugmessage.message = message.id
      AND bugmessage.bug = 15
      AND (message.parent IS NULL OR message.parent IN (
             SELECT message FROM bugmessage WHERE bug = 15))) AS indexed_messages
 WHERE index > 2
   AND index <= 4;