Book Image

PostgreSQL High Availability Cookbook - Second Edition

By : Shaun Thomas
Book Image

PostgreSQL High Availability Cookbook - Second Edition

By: Shaun Thomas

Overview of this book

Databases are nothing without the data they store. In the event of a failure - catastrophic or otherwise - immediate recovery is essential. By carefully combining multiple servers, it’s even possible to hide the fact a failure occurred at all. From hardware selection to software stacks and horizontal scalability, this book will help you build a versatile PostgreSQL cluster that will survive crashes, resist data corruption, and grow smoothly with customer demand. It all begins with hardware selection for the skeleton of an efficient PostgreSQL database cluster. Then it’s on to preventing downtime as well as troubleshooting some real life problems that administrators commonly face. Next, we add database monitoring to the stack, using collectd, Nagios, and Graphite. And no stack is complete without replication using multiple internal and external tools, including the newly released pglogical extension. Pacemaker or Raft consensus tools are the final piece to grant the cluster the ability to heal itself. We even round off by tackling the complex problem of data scalability. This book exploits many new features introduced in PostgreSQL 9.6 to make the database more efficient and adaptive, and most importantly, keep it running.
Table of Contents (18 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Using a foreign table in a query

Foreign tables exist as empty shells on the local database, lending merely their structure for query-planning and data-fetching purposes. The foreign data wrapper transforms data requests to something the remote server can understand and presents it in a way PostgreSQL will recognize.

As we're using the postgres_fdw wrapper, the situation is simplified. A PostgreSQL server should have less trouble communicating with another PostgreSQL server than an Oracle server, for instance. Though this means less transformation, there are still limitations on what functionality a foreign table might provide compared to a local table.

In this recipe, we'll use a foreign table in a few scenarios and examine how it performs in each. We'll also explore some of the common caveats involved in foreign table access.

Getting ready

As we will be using the pgbench_accounts foreign table in this recipe, please follow all the previous recipes before proceeding.

How to do it...

All queries...