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PostgreSQL 10 High Performance

You're reading from   PostgreSQL 10 High Performance Expert techniques for query optimization, high availability, and efficient database maintenance

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Product type Paperback
Published in Apr 2018
Publisher Packt
ISBN-13 9781788474481
Length 508 pages
Edition 3rd Edition
Languages
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Author (1):
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Enrico Pirozzi Enrico Pirozzi
Author Profile Icon Enrico Pirozzi
Enrico Pirozzi
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Table of Contents (18) Chapters Close

Preface 1. PostgreSQL Versions FREE CHAPTER 2. Database Hardware 3. Database Hardware Benchmarking 4. Disk Setup 5. Memory for Database Caching 6. Server Configuration Tuning 7. Routine Maintenance 8. Database Benchmarking 9. Database Indexing 10. Query Optimization 11. Database Activity and Statistics 12. Monitoring and Trending 13. Pooling and Caching 14. Scaling with Replication 15. Partitioning Data 16. Avoiding Common Problems 17. Other Books You May Enjoy

EXPLAIN basics

If you have a query that's running slowly, the first thing to try is running it with EXPLAIN before the statement executes. This displays what's called a query plan, the list of what's expected to happen when that query is executed. If you instead use EXPLAIN ANALYZE before the statement, you'll get both the estimation describing what the planner expected, along with what actually happened when the query ran. Note that this form will actually execute the statement as if you run it manually. Consider the following statement:

EXPLAIN ANALYZE DELETE * FROM t;

This is not only going to show you a query plan for deleting those rows, it's going to delete them; that's the only way to know for sure how long actually executing the plan is going to take. It's much harder to get a consistent setup to compare timing of operations that do INSERT...

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