PostgreSQL is a complex system that includes users, databases, and data. In order to be able to interact with a database in the cluster, you need to have at least one user. By default, when installing a new cluster, a single administrator user (named postgres) is created. While it is possible to handle all the connections, applications, and databases with that single administrative user, it is much better to create different users with different properties and privileges, as well as login credentials, for every specific task.

PostgreSQL provides a very rich user-management structure, and single users can be grouped into a variety of different groups at the same time. Moreover, groups can be nested within other groups, so that you can have a very accurate representation of your account model. Thanks to this accurate representation, and thanks to the...