Caching workspace listings

Apart from the public listings which are cached, queries in viewlets and 
listings or any other part of Bungeni are not cached. There is a need to have a 
consistent way of caching to be used everywhere in Bungeni.  Sqlalchemy 
supports caching through the use of the 
Beaker[http://beaker.groovie.org/index.html]. Beaker can be configured to use 
different kinds of caching backends such as files, memory and 
memcached[http://en.wikipedia.org/wiki/Memcached]. 

In the example below from the ORM definition for parliamentary items, the users 
table is queried and a User object created for every parliamentary item 
returned by a query to the parliamentary items table

mapper(domain.ParliamentaryItem, schema.parliamentary_items,
    polymorphic_on=schema.parliamentary_items.c.type,
    polymorphic_identity="item",
    properties={
        "owner": relation(domain.User,
            primaryjoin=rdb.and_(schema.parliamentary_items.c.owner_id ==
                schema.users.c.user_id),
            uselist=False,
            lazy=False),
            ....
    }
}

All queries to the parliamentary_items table would be much faster if User 
objects were cached. The owner property would be changed to be a lazy loaded 
property which is then loaded from cache. There are several relationships that 
have "lazy=False" defined on them that would benefit from this change.

There is an example of this technique 
here[http://www.sqlalchemy.org/trac/browser/examples/beaker_caching/caching_quer
y.py]. This could be implemented in such a way that all the queries in Bungeni 
do not have to be modified.

For queries that would benefit from more aggressive caching, eg. for 
parliamentary items in the workspace, queries would be changed to first query 
the database for the id's of the relevant documents then check if they are 
there in the cache, if not a database query is executed to get the item which 
is then added to the cache.
Original issue reported on code.google.com by ashok.ha...@gmail.com on 15 Nov 2011 at 7:36
BenoitTalbot / bungeni-portal

Caching workspace listings #739
