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)
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Index

Event triggers

Rules and triggers act as DML statements, which means they are triggered by something that changes the data but not the data layout or the table properties. PostgreSQL provides so-called event triggers, which are particular triggers that fire on DDL statements. The purpose of the event trigger, therefore, is to manage and react to events that will change the data structure rather than the data content. Triggers can be used in many ways to enforce specific policies across your databases.

Once fired, an event trigger receives an event and a command tag, both of which are useful for introspection and providing information about what fired the trigger. In particular, the command tag contains a description of the command (for example, CREATE or ALTER), while the event contains the category that fired the trigger – in particular, the following:

  • ddl_command_start and ddl_command_end indicate, respectively, the beginning and the completion of the DDL command...