How can I drop relations in a PostgreSQL database without foreign key check?
I've got it.

For a single table I can do:

DROP TABLE "tableName" CASCADE


For all tables inside a schema, for example "public", I can do:

DROP SCHEMA public CASCADE;
CREATE SCHEMA public;


Source:

http://www.postgresql.org/docs/current/static/sql-droptable.html

https://stackoverflow.com/a/13823560/937110

Or, as suggested by a_horse_with_no_name:

DROP OWNED BY name [, ...] [ CASCADE | RESTRICT ]


source:
http://postgresql.org/docs/current/static/sql-drop-owned.html