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

Observing deadlocks and similar issues

Deadlocks are an important issue and can happen in every database I am aware of. Basically, a deadlock will happen if two transactions have to wait on each other.

In this section, you will see how this can happen. Let us suppose we have a table containing two rows:

CREATE TABLE t_deadlock (id int);
INSERT INTO t_deadlock VALUES (1), (2);

The next listing shows what can happen:

Transaction 1

Transaction 2

BEGIN;

BEGIN;

UPDATE t_deadlock SET id = id * 10 WHERE id = 1;

UPDATE t_deadlock SET id = id * 10 WHERE id = 2;

UPDATE t_deadlock SET id = id * 10 WHERE id = 2;

Waiting on transaction 2

UPDATE t_deadlock SET id = id * 10 WHERE id = 1;

Waiting on transaction 2

Waiting on transaction 1

Deadlock will be resolved after one second (deadlock_timeout)

COMMIT;

ROLLBACK;

As soon as the deadlock is detected, the following error message...