3 Ways to See all Users and Permissions in PostgreSQL

Overview

Managing users and their permissions is a critical aspect of database administration. PostgreSQL, as a powerful open-source relational database system, provides several ways to handle this task efficiently. Knowing who has access to what data is pivotal for maintaining database security. In this guide, we’ll walk through several methods to view all users and their permissions in a PostgreSQL database.

Querying pg_roles

The pg_roles view allows you to list all roles in the PostgreSQL database system. A role can function as a database user, a group, or both, and comes with its set of permissions.

What to do?

• Connect to your PostgreSQL database using a command-line interface, like psql, or use a graphical interface such as pgAdmin.
• Run a SELECT query on the pg_roles view to get information about all roles. You can include additional filters depending on your needs.

Execute this SELECT statement:

SELECT rolname FROM pg_roles;

Advantages: Quick, simple, and easy to remember. Directly queries a built-in PostgreSQL catalog.

Limitations: pg_roles does not show explicit permissions on databases or tables, it simply lists roles.

Access Control Lists (ACL) Inspection

Access Control Lists (ACLs) are the underlying structure that PostgreSQL uses to store permissions for databases, schemas, and tables. You can inspect this information with certain SQL queries that decrypt the ACL format into human-readable permissions.

Here are what we’re going to do:

• Connect to the PostgreSQL database.
• Run a query combining information from various PostgreSQL system catalogs, like pg_class and pg_namespace, to fetch the ACL data.

The query:

SELECT nspname, relname, relacl FROM pg_class c JOIN pg_namespace n ON (c.relnamespace = n.oid);

Advantages: Allows you to see the exact privileges granted on specific objects.

Limitations: Can be complex for newcomers and requires understanding of the ACL format.

Utilizing pg_permissions Extension

The pg_permissions extension provides user-friendly functions to view permissions across all objects for a particular role. However, it might not be installed by default in all PostgreSQL installations.

Here’s the process to get it done:

• Check if pg_permission is installed by running SELECT * FROM pg_available_extensions; If it’s not listed, you’ll need to install it by running CREATE EXTENSION pg_permissions;
• Once installed, use the provided functions to list user permissions.

The query to run:

SELECT * FROM view_all_role_permissions('rolename');

Advantages: Intuitive function names make it easy to query for role permissions.

Limitations: Requires the installation of an additional extension, which might not have support in all environments.

Conclusion

In this guide, we explored multiple ways to view all users and their permissions in a PostgreSQL database. Whether through direct queries into system catalogs like pg_roles and ACLs, or utilizing extensions like pg_permissions, PostgreSQL administrators have the tools they need to audit and manage access control. Each method has its pros and cons regarding complexity, level of detail, and ease of use. The choice of method will largely depend upon the administrator’s familiarity with PostgreSQL system catalogs, the complexity of the database permissions structure, and whether additional extensions can be installed in the environment.