Book Image

Mastering PostgreSQL 9.6

By : Hans-Jürgen Schönig
Book Image

Mastering PostgreSQL 9.6

By: Hans-Jürgen Schönig

Overview of this book

PostgreSQL is an open source database used for handling large datasets (Big Data) and as a JSON document database. It also has applications in the software and web domains. This book will enable you to build better PostgreSQL applications and administer databases more efficiently. We begin by explaining the advanced database design concepts in PostgreSQL 9.6, along with indexing and query optimization. You will also see how to work with event triggers and perform concurrent transactions and table partitioning, along with exploring SQL and server tuning. We will walk you through implementing advanced administrative tasks such as server maintenance and monitoring, replication, recovery and high availability, and much more. You will understand the common and not-so-common troubleshooting problems and how you can overcome them. By the end of this book, you will have an expert-level command of the advanced database functionalities and will be able to implement advanced administrative tasks with PostgreSQL.
Table of Contents (14 chapters)
Free Chapter
1
PostgreSQL Overview

Understanding transaction isolation levels

Up to now, you have seen how to handle locking as well as some basic concurrency. In this section, you will learn about transaction isolation. To me, this is one of the most neglected topics in modern software development. Only a small fraction of software developers are actually aware of this issue, which in turn leads to disgusting and mind-boggling bugs.

Here is an example of what can happen:

Transaction 1

Transaction 2

BEGIN;

SELECT sum(balance) FROM t_account;

User will see 300

BEGIN;

INSERT INTO t_account (balance) VALUES (100);

COMMIT;

SELECT sum(balance) FROM t_account;

User will see 400

COMMIT;

Most users would actually expect the left transaction to always return 300 regardless of the second transaction. However, this is not true. By default, PostgreSQL runs in READ COMMITTED transaction isolation mode. This means...