I've written a HOWTO on how to create new aggregate functions to
create list (comma lists, HTML lists, etc.). It explains the purpose
of these, and gives an example of how to create one in pgplsql.
The HOWTO is written for the Zope site, but it's not really Zope-
or Python- specific.
http://www.zope.org/Members/pupq/pg_in_aggregates
Hoping someone finds it useful.
Cheers,
--
Joel Burton <jburton@scw.org>
Director of Information Systems, Support Center of Washington