Book Image

PostgreSQL 11 Administration Cookbook

By : Simon Riggs, Gianni Ciolli, Meesala
Book Image

PostgreSQL 11 Administration Cookbook

By: Simon Riggs, Gianni Ciolli, Meesala

Overview of this book

PostgreSQL is a powerful, open source database management system with an enviable reputation for high performance and stability. With many new features in its arsenal, PostgreSQL 11 allows you to scale up your PostgreSQL infrastructure. This book takes a step-by-step, recipe-based approach to effective PostgreSQL administration. The book will introduce you to new features such as logical replication, native table partitioning, additional query parallelism, and much more to help you to understand and control, crash recovery and plan backups. You will learn how to tackle a variety of problems and pain points for any database administrator such as creating tables, managing views, improving performance, and securing your database. As you make steady progress, the book will draw attention to important topics such as monitoring roles, backup, and recovery of your PostgreSQL 11 database to help you understand roles and produce a summary of log files, ensuring high availability, concurrency, and replication. By the end of this book, you will have the necessary knowledge to manage your PostgreSQL 11 database efficiently.
Table of Contents (19 chapters)
Title Page
Copyright and Credits
About Packt
Contributors
Preface
Index

Checking whether a user is connected


Here, we will show you how to learn whether a certain database user is currently connected to the database.

Getting ready

If you are logged in as a superuser, you will have full access to monitoring information.

How to do it…

Issue the following query to see whether the user bob is connected:

SELECT datname FROM pg_stat_activity WHERE usename = 'bob';

If this query returns any rows, then it that means bob is connected to the database. The returned value is the name of the database to which the user is connected.

How it works…

PostgreSQL's pg_stat_activity system view keeps track of all running PostgreSQL backends. This includes information such as the query that is being currently executed, or the last query that was executed by each backend, who is connected, when the connection, the transaction, and/or the query were started, and so on.

There's more…

Please spend a few minutes reading the PostgreSQL documentation, which contains more detailed information about...