Book Image

Learn PostgreSQL - Second Edition

By : Luca Ferrari, Enrico Pirozzi
1 (2)
Book Image

Learn PostgreSQL - Second Edition

1 (2)
By: Luca Ferrari, Enrico Pirozzi

Overview of this book

The latest edition of this PostgreSQL book will help you to start using PostgreSQL from absolute scratch, helping you to quickly understand the internal workings of the database. With a structured approach and practical examples, go on a journey that covers the basics, from SQL statements and how to run server-side programs, to configuring, managing, securing, and optimizing database performance. This new edition will not only help you get to grips with all the recent changes within the PostgreSQL ecosystem but will also dig deeper into concepts like partitioning and replication with a fresh set of examples. The book is also equipped with Docker images for each chapter which makes the learning experience faster and easier. Starting with the absolute basics of databases, the book sails through to advanced concepts like window functions, logging, auditing, extending the database, configuration, partitioning, and replication. It will also help you seamlessly migrate your existing database system to PostgreSQL and contains a dedicated chapter on disaster recovery. Each chapter ends with practice questions to test your learning at regular intervals. By the end of this book, you will be able to install, configure, manage, and develop applications against a PostgreSQL database.
Table of Contents (22 chapters)
20
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Index

Exploring physical backups

A physical backup is a low-level backup that’s taken during the normal operations of the database cluster. Here, low-level means that the backup is somehow performed “externally” to the backup cluster – that is, at the filesystem level.

As you already know from Chapter 10, Users, Roles, and Database Security, the database cluster requires both the data files contained in PGDATA/base and the WALs contained in PGDATA/wal, as well as a few other files, to make the cluster work properly. The main concept, however, is that the data files and the WALs can make the cluster self-healing and recover from a crash. Hence, a physical backup performs a copy of all the cluster files and then, when the restore is required, it simulates a database crash and makes the cluster self-heal with the WALs in place.

The reason why physical backups are important is that they allow us to effectively clone a cluster, starting from the files it is...