Book Image

Mastering PostgreSQL 9.6

By : Hans-Jürgen Schönig
Book Image

Mastering PostgreSQL 9.6

By: Hans-Jürgen Schönig

Overview of this book

PostgreSQL is an open source database used for handling large datasets (Big Data) and as a JSON document database. It also has applications in the software and web domains. This book will enable you to build better PostgreSQL applications and administer databases more efficiently. We begin by explaining the advanced database design concepts in PostgreSQL 9.6, along with indexing and query optimization. You will also see how to work with event triggers and perform concurrent transactions and table partitioning, along with exploring SQL and server tuning. We will walk you through implementing advanced administrative tasks such as server maintenance and monitoring, replication, recovery and high availability, and much more. You will understand the common and not-so-common troubleshooting problems and how you can overcome them. By the end of this book, you will have an expert-level command of the advanced database functionalities and will be able to implement advanced administrative tasks with PostgreSQL.
Table of Contents (14 chapters)
Free Chapter
PostgreSQL Overview

Making use of replication slots

After this introduction to synchronous replication and dynamically adjustable durability I want to focus your attention on a feature called replication slots.

What is the purpose of a replication slot? Let us consider the following example: there is a master and a slave. On the master, a large transaction is executed and the network connection is not fast enough to ship all the data in time. At some point, the master removes its transaction log (checkpoint). If the slave is too far behind, a re-sync is needed. As you have already seen, the wal_keep_segments setting can be used to reduce the risk of failing replication. The question is this: what is the best value for the wal_keep_segments setting? Sure, more is better, but how much is best?

Replication slots will solve this problem for you: if you are using a replication slot, a master can only recycle the transaction log once it...