Another interesting alternative could be using or writing a PostgreSQL foreign data wrapper.

There is one that supports tabular data (file_fdw), and another one for JSON files (json_fdw). If you have files in other formats, you can also write your fdw for it. This way, you get complete SQL coverage.

Also, if you don't want to pay the overhead of parsing the file every time, you can use the new materialized feature for caching: http://www.postgresql.org/docs/9.3/static/rules-materialized...

(Disclaimer: Enthused Postgres user.)