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PostgreSQL 9 Administration Cookbook - Second Edition

You're reading from  PostgreSQL 9 Administration Cookbook - Second Edition

Product type Book
Published in Apr 2015
Publisher Packt
ISBN-13 9781849519069
Pages 504 pages
Edition 1st Edition
Languages
Toc

Table of Contents (19) Chapters close

PostgreSQL 9 Administration Cookbook Second Edition
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
1. First Steps 2. Exploring the Database 3. Configuration 4. Server Control 5. Tables and Data 6. Security 7. Database Administration 8. Monitoring and Diagnosis 9. Regular Maintenance 10. Performance and Concurrency 11. Backup and Recovery 12. Replication and Upgrades Index

Forcing a query to use an index


Here, we will show you how to force the database to use an index. In fact, it is not possible to tell PostgreSQL to use an index by submitting an access path hint, like other DBMS products do. However, you can trick it into using an index by telling the optimizer that all other options are prohibitively expensive.

Getting ready

First, you have to make sure that it is worth it to use the index. This is best done on a development or testing system, but if you are careful, it can also be done on the production server. Sometimes, it is very hard to generate a load similar to a live system in a test environment, and then your best option may be to carefully test it on the production server.

As the PostgreSQL optimizer does not take into account the parallel load caused by other backends, it may make sense to lie to PostgreSQL about some statistics in order to make it use indexes.

How to do it…

Try running this command:

SET enable_seqscan TO false;

Here, you tell PostgreSQL...

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