Use pool library instead of epgsql_pool or emysql

[manuel-rubio]

Instead of use specific pools for each driver, the idea is use poolboy or wpool instead to use only one pool library for all of the SQL possibilities.

[tsloughter]

I'd suggest against poolboy. It just isn't a good fit for database connection pooling. You should checkout https://github.com/SpaceTime-IoT/pgo/blob/master/src/pgo_pool.erl which i stole from elixir-ecto/db_connection#108 :)

[manuel-rubio]

@tsloughter I could suggest to create a dbi_pgo project if you want. My idea is provide different providers to the coders can choose but keeping dbi as core base.

[manuel-rubio]

In https://github.com/dbi-beam/dbi_pgsql and https://github.com/dbi-beam/dbi_mysql is implemented poolboy as pool for connections so, it's done.

[tsloughter]

Ah ok, didn't realize it was already done.

[manuel-rubio]

@tsloughter I did it today :-P