How to determine what type of index to use in Postgres?

Question

I have a Postgres database that has 2 columns that are not primary keys (nor can be), but are searched on a lot and are compared for equality to 2 columns in other tables.

Answer 1

Try to understand the queryplanner as well, because this part of PostgreSQL has to work with your indexes. EXPLAIN ANALYZE will be essential to optimise your queries.