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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21
Index

Transaction isolation levels

In a concurrent database system, you could encounter three different problems:

  • Dirty reads: A dirty read happens when the database allows a transaction to see work-in-progress data from other not-yet-finished transactions. In other words, data that has not been consolidated is visible to other transactions. No production-ready database allows that, and PostgreSQL is no exception: you are assured your transaction will only perceive data that has been consolidated, and in order to be consolidated, the transactions that created such data must be complete.
  • Unrepeatable reads: An unrepeatable read happens when the same query, within the same transaction, executed multiple times, perceives a different set of data. This essentially means that the data has changed between two sequential executions of the same query in the same transaction. PostgreSQL does not allow this kind of problem by means of snapshots: every transaction can perceive the...