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)
1
Section 1: Getting Started
5
Section 2: Interacting with the Database
12
Section 3: Administering the Cluster
20
Section 4: Replication
23
Section 5: The PostegreSQL Ecosystem

Deadlocks

A deadlock is an event that happens when different transactions depend on each other in a circular way. Deadlocks are, to some extent, normal events in a concurrent database environment and nothing an administrator should worry about, unless they become extremely frequent, meaning there is some dependency error in the applications and the transactions.

When a deadlock happens, there is no choice but to terminate the locked transactions. PostgreSQL has a very powerful deadlock detection engine that does exactly this job: it finds stalled transactions and, in the case of a deadlock, terminates them (producing ROLLBACK).

In order to produce a deadlock, imagine two concurrent transactions applying changes to the very same tuples in a conflicting way. For example, the first transaction could do something like the following:

-- session 1
forumdb=> BEGIN;
BEGIN
forumdb=> SELECT txid_current();
txid_current
--------------
4875
(1 row)

forumdb=> UPDATE tags SET tag = &apos...