Book Image

PostgreSQL High Performance Cookbook

By : Chitij Chauhan, Dinesh Kumar
Book Image

PostgreSQL High Performance Cookbook

By: Chitij Chauhan, Dinesh Kumar

Overview of this book

PostgreSQL is one of the most powerful and easy to use database management systems. It has strong support from the community and is being actively developed with a new release every year. PostgreSQL supports the most advanced features included in SQL standards. It also provides NoSQL capabilities and very rich data types and extensions. All of this makes PostgreSQL a very attractive solution in software systems. If you run a database, you want it to perform well and you want to be able to secure it. As the world’s most advanced open source database, PostgreSQL has unique built-in ways to achieve these goals. This book will show you a multitude of ways to enhance your database’s performance and give you insights into measuring and optimizing a PostgreSQL database to achieve better performance. This book is your one-stop guide to elevate your PostgreSQL knowledge to the next level. First, you’ll get familiarized with essential developer/administrator concepts such as load balancing, connection pooling, and distributing connections to multiple nodes. Next, you will explore memory optimization techniques before exploring the security controls offered by PostgreSQL. Then, you will move on to the essential database/server monitoring and replication strategies with PostgreSQL. Finally, you will learn about query processing algorithms.
Table of Contents (19 chapters)
PostgreSQL High Performance Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Working on semi and anti joins


In this recipe, we will be discussing hash different joining methods.

Getting ready

Semi or anti joins are kind of sub join types to the joining methods such as hash, merge, and nested loop, where the optimizer prefers to use them for EXISTS/IN or NOT EXISTS/NOT IN operators.

Semi join will return a single value for all the matching records from the other table. That is, if the second table has multiple matching entries for the first table's record, then it will return only one copy from the first table. However, a normal join it will return multiple copies from the first table.

Anti-join will return rows, when no matching records are found in the second table. It is quite opposite to the semi join, since it is returning records from the first table, when there is no match in the second table.

How to do it…

Let's run a query in the benchmarksql database to get the list of items that are in stock:

benchmarksql=#
EXPLAIN SELECT * FROM bmsql_item WHERE EXISTS (SELECT...