Scaling with GridSQL
Another way you might be able to approach hash-based distribution among nodes is using GridSQL, refer http://www.enterprisedb.com/community/projects/gridsql.do.
Instead of putting the logic for what node to execute against directly into the database, GridSQL provides a client that speaks to a node co-ordinator process that handles that job. This process is all relatively transparent to you. The main catch is that not all PostgreSQL features are available, and you need a client driver compatible with GridSQL.
GridSQL uses its own parser, planner, and optimizer, accepting ANSI standard SQL but not all of PostgreSQL's syntax. The driver interface for your applications to talk to the database can look like a standard PostgreSQL one, but not everything a full PostgreSQL application expects will be supported. In stark contrast to PL/Proxy style scaling, instead of relying heavily on the database functions, GridSQL doesn't support running them at all!
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