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

Understanding the basic concepts of logical replication

Logical replication is a method that we can use to replicate data based on the concept of identity replication. REPLICA IDENTITY is a parameter present in table management commands (such as CREATE TABLE and ALTER TABLE); this parameter is used by PostgreSQL to obtain additional information within WAL segments, to recognize which tuples have been eliminated and which tuples have been updated. The REPLICA IDENTITY parameter can take four values:

  • DEFAULT
  • USING INDEX index_name
  • FULL
  • NOTHING

The concept behind logical replication is to pass the logic of the commands executed on the primary machine to the server and not the exact copy of the blocks to be replicated, byte by byte. At the heart of logical replication, there is a reverse engineering process that, starting from the WAL segments and using a logical decoding process, is able to extrapolate the original SQL commands and pass them on to...