Hi Michael,
You could streamline your recursive walk by using a temporary table and
a database procedure. The temporary table would hold the ids you
recursively harvest. It would be populated by your database procedure,
which would walk up the levels of your hierarchy. When the procedure
returned, you could then join the temporary table to your
discussion_item table to get the details you needed. It's not an elegant
solution, but by running the procedure inside the database, you would
eliminate a lot of network handshaking.
Derby does not support hierarchical queries. You're welcome to log an
enhancement request for this feature.
Regards,
-Rick
Michael McCutcheon wrote:
I need to implement an online discussion forum, similar to JavaLobby.
Similar kinds of discussion forums tend to use recursive selects, so
that in a single select, all of the items for a particular discussion
thread (and all sub threads, and their sub threads, etc) may be
retrieved.
For a table, I'm thinking of something like this:
create table discussion_item
(
id integer not null,
parent_id integer not null,
creator_user_id varchar,
title varchar,
message varchar
)
There needs to be some kind of recursive functionality to select a
item, and it's parents, and it's parents, etc.
Does Derby support any kind of recursive selecting? I know that this
is supported in Oracle and other databases.
If it does not, is it planned to have it in the future?
If not, are there any ways of handling scenarios like this without
having to do a select for each item?
Thanks for any input.
Mike
