Book Image

Learn PostgreSQL

By : Luca Ferrari, Enrico Pirozzi
Book Image

Learn PostgreSQL

By: Luca Ferrari, Enrico Pirozzi

Overview of this book

PostgreSQL is one of the fastest-growing open source object-relational database management systems (DBMS) in the world. As well as being easy to use, it’s scalable and highly efficient. In this book, you’ll explore PostgreSQL 12 and 13 and learn how to build database solutions using it. Complete with hands-on tutorials, this guide will teach you how to achieve the right database design required for a reliable environment. You'll learn how to install and configure a PostgreSQL server and even manage users and connections. The book then progresses to key concepts of relational databases, before taking you through the Data Definition Language (DDL) and commonly used DDL commands. To build on your skills, you’ll understand how to interact with the live cluster, create database objects, and use tools to connect to the live cluster. You’ll then get to grips with creating tables, building indexes, and designing your database schema. Later, you'll explore the Data Manipulation Language (DML) and server-side programming capabilities of PostgreSQL using PL/pgSQL, before learning how to monitor, test, and troubleshoot your database application to ensure high-performance and reliability. By the end of this book, you'll be well-versed with the Postgres database and be able to set up your own PostgreSQL instance and use it to build robust solutions.
Table of Contents (27 chapters)
Section 1: Getting Started
Section 2: Interacting with the Database
Section 3: Administering the Cluster
Section 4: Replication
Section 5: The PostegreSQL Ecosystem

Event triggers

Rules and triggers act as Data Manipulation Level (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 (Data Definition Level) statements. The purpose of the event trigger is therefore to manage and react to events that are going to 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...