Book Image

Mastering PostgreSQL 10

Book Image

Mastering PostgreSQL 10

Overview of this book

PostgreSQL is an open source database used for handling large datasets (big data) and as a JSON document database. This book highlights the newly introduced features in PostgreSQL 10, and shows you how you can build better PostgreSQL applications, and administer your PostgreSQL database more efficiently. We begin by explaining advanced database design concepts in PostgreSQL 10, 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, high availability, and much more. You will understand 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 advanced database functionalities and will be able to implement advanced administrative tasks with PostgreSQL 10.
Table of Contents (15 chapters)

Understanding transaction isolation levels

Up until now, you have seen how to handle locking as well as some basic concurrency. In this section, you will learn 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 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 the READ COMMITTED transaction...