1. Changed cleanup sweep interval to 15 minutes
2. Fixed broken PostgreSQL and Oracle queries that were supposed to select
notifications for deletion but rather returned all notifications if any
were ripe for deletion, causing seemingly random failure to deliver
notifications. Sloan had hacked this with a kludge to only delete
notifications older than two days but this didn't work on openacs.org,
which supports weekly summaries of notifications.
3. Changed notification::new to not insert notifications that have no
pending requests. This avoids having to waste time deleting them
afterwards.
4. Added notification_request::request_exists which returns true if
there's at least one notification request for a given object and
notification type.
5. Added a couple of indexes to speed queries that ran slow on openacs.org.
