High CPU usage for channels with lots of members

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Channel lwt has hundreds of members, and this leads to high CPU usage for all 
requests/XMPP 
messages that it receives. I'm suspecting that this is caused by 
attachUsersToChannelMembers/getUsersByChannel. Sample Appstats output for one 
of their 
messages:

http://partychapp.appspot.com/appstats/details?time=1273421263242

In case it's gone, screenshot at:

http://skitch.com/mihaiparparita/dnir5/appstats-partychapp

All of the datastore_v3.Next calls is paging through the query that 
getUsersByChannel does.

Ideally we shouldn't load the User for every Member at all, we don't care about 
it (except for the 
requesting user's User).

Original issue reported on code.google.com by mihai.parparita on 9 May 2010 at 4:10