Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Overview of this book

PostgreSQL is a powerful opensource database management system; now recognized as the expert's choice for a wide range of applications, it has an enviable reputation for performance and stability. PostgreSQL provides an integrated feature set comprising relational database features, object-relational, text search, Geographical Info Systems, analytical tools for big data and JSON/XML document management. Starting with short and simple recipes, you will soon dive into core features, such as configuration, server control, tables, and data. You will tackle a variety of problems a database administrator usually encounters, from creating tables to managing views, from improving performance to securing your database, and from using monitoring tools to using storage engines. Recipes based on important topics such as high availability, concurrency, replication, backup and recovery, as well as diagnostics and troubleshooting are also given special importance. By the end of this book, you will have all the knowledge you need to run, manage, and maintain PostgreSQL efficiently.
Table of Contents (13 chapters)

Restricting users to only one session each

If resources need to be closely controlled, you may wish to restrict users so that they can only connect at most once to the server. The same technique can be used to prevent connections entirely for that user.

How to do it...

We can restrict users to only one connection using the following command:

postgres=# ALTER ROLE fred CONNECTION LIMIT 1;
ALTER ROLE

This will then cause any additional connections to receive the error message:

FATAL: too many connections for role "fred".

You can eliminate this restriction by setting the value to -1.

It's possible to set the limit to zero or any positive integer. You can set this to a number other than max_connections, though it...