When you have primary keys generated by the database not by the application, then you might need it to be returned. In postgres you have to use RETURNING function in your sql query in order to have...
PostgreSQL, often simply Postgres, is an object-relational database management system (ORDBMS) available for many platforms including Linux, FreeBSD, Solaris, Microsoft Windows and Mac OS X.[4] It is released under the PostgreSQL License, which is an MIT-style license, and is thus free and open source software.