How can I speed up update/replace operations in PostgreSQL?

Question

We have a rather specific application that uses PostgreSQL 8.3 as a storage backend (using Python and psycopg2). The operations we perform to the important tables are in the ma

Answer 1

The usual way I do these things in pg is: load raw data matching target table into temp table (no constraints) using copy, merge(the fun part), profit.

I wrote a merge_by_key function specifically for these situations:

http://mbk.projects.postgresql.org/

The docs aren't terribly friendly, but I'd suggest giving it a good look.