Book Image

Mastering PostgreSQL 15 - Fifth Edition

By : Hans-Jürgen Schönig
Book Image

Mastering PostgreSQL 15 - Fifth Edition

By: Hans-Jürgen Schönig

Overview of this book

Starting with an introduction to the newly released features of PostgreSQL 15, this updated fifth edition will help you get to grips with PostgreSQL administration and how to build dynamic database solutions for enterprise apps, including designing both physical and technical aspects of the system. You'll explore advanced PostgreSQL features, such as logical replication, database clusters, advanced indexing, and user management to manage and maintain your database. You'll then work with the PostgreSQL optimizer, configure PostgreSQL for high speed, and move from Oracle to PostgreSQL. Among the other skills that the book will help you build, you’ll cover transactions, handling recursions, working with JSON and JSONB data, and setting up a Patroni cluster. It will show you how to improve performance with query optimization. You'll also focus on managing network security and work with backups and replication while exploring useful PostgreSQL extensions that optimize the performance of large databases. By the end of this PostgreSQL book, you’ll be able to use your database to its utmost capacity by implementing advanced administrative tasks with ease.
Table of Contents (16 chapters)

Making use of replication slots

After that introduction to synchronous replication and dynamically adjustable durability, I want to focus on a feature called replication slots.

What is the purpose of a replication slot? Let’s 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 data in time. At some point, the master removes its transaction log (checkpoint). If the slave is too far behind, a resync is needed. As we 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 us – if we are using a replication slot, a master can only recycle the transaction log once it has been consumed by all replicas. The advantage here is...