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

Checking for slow queries

After inspecting pg_stat_activity, it makes sense to take a look at slow, time-consuming queries. Basically, there are two ways to approach the problem:

  • Look for individual slow queries in the log
  • Look for types of queries that take too much time

Finding single, slow queries is the classical approach to performance tuning. By setting the log_min_duration_statement variable to a desired threshold, PostgreSQL will start to write a log line for each query exceeding this threshold. By default, the slow query log is off:

test=# SHOW log_min_duration_statement; 
log_min_duration_statement
----------------------------
-1
(1 row)

However, setting this variable to a reasonable good value makes perfect sense. Depending on your workload, the desired time might of course vary.

In many cases, the desired value might differ from database to database. Therefore, it is also possible to use the variable...