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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

Query plan node structure

EXPLAIN output is organized into a series of plan nodes. At the lowest level, there are nodes that look at tables, scanning them, or looking things up with an index. Higher-level nodes take the output from the lower-level ones and operate on it. When you run EXPLAIN, each line in the output is a plan node.

Each node has several numeric measurements associated with it as well:

# EXPLAIN ANALYZE SELECT * FROM customers;
QUERY PLAN                                                   
----------
Seq Scan on customers  (cost=0.00..676.00 rows=20000 width=268) (actual time=0.011..34.489 rows=20000 loops=1)
Total runtime: 65.804 ms  

This plan has one node, a Seq Scan node. The first set of numbers reported are the plan estimates, which are the only things you see if you run EXPLAIN without ANALYZE:

  • cost=0.00..676.00: The first cost here is the startup cost of...
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