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Mastering PostgreSQL 15

You're reading from   Mastering PostgreSQL 15 Advanced techniques to build and manage scalable, reliable, and fault-tolerant database applications

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Product type Paperback
Published in Jan 2023
Publisher Packt
ISBN-13 9781803248349
Length 522 pages
Edition 5th Edition
Languages
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Author (1):
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Hans-Jürgen Schönig Hans-Jürgen Schönig
Author Profile Icon Hans-Jürgen Schönig
Hans-Jürgen Schönig
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Toc

Table of Contents (16) Chapters Close

Preface 1. Chapter 1: PostgreSQL 15 Overview 2. Chapter 2: Understanding Transactions and Locking FREE CHAPTER 3. Chapter 3: Making Use of Indexes 4. Chapter 4: Handling Advanced SQL 5. Chapter 5: Log Files and System Statistics 6. Chapter 6: Optimizing Queries for Good Performance 7. Chapter 7: Writing Stored Procedures 8. Chapter 8: Managing PostgreSQL Security 9. Chapter 9: Handling Backup and Recovery 10. Chapter 10: Making Sense of Backups and Replication 11. Chapter 11: Deciding on Useful Extensions 12. Chapter 12: Troubleshooting PostgreSQL 13. Chapter 13: Migrating to PostgreSQL 14. Index 15. Other Books You May Enjoy

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 this 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 classic approach to performance tuning. By setting the log_min_duration_statement variable to a desired threshold, PostgreSQL will start to write a logline for each query that exceeds this threshold. By default, the slow query log is off, as follows:

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

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

In...

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