Materialized views

One of the most effective ways to speed up queries against large data sets that are run more than once is to cache the result in a materialized view, essentially a view that is run and its output stored for future reference. Work on adding these into the core database is in progress, but like counting it's possible to build them right now using features such as triggers. See http://wiki.postgresql.org/wiki/Materialized_Views for comments on the state-of-the-art here, and pointers to code samples. If you have views derived from large tables in the database, few techniques are as effective as materializing those views and optimizing their updates for improving query performance.