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PostgreSQL 14 Administration Cookbook

You're reading from   PostgreSQL 14 Administration Cookbook Over 175 proven recipes for database administrators to manage enterprise databases effectively

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Product type Paperback
Published in Mar 2022
Publisher Packt
ISBN-13 9781803248974
Length 608 pages
Edition 1st Edition
Concepts
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Authors (2):
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Gianni Ciolli Gianni Ciolli
Author Profile Icon Gianni Ciolli
Gianni Ciolli
Simon Riggs Simon Riggs
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Simon Riggs
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Toc

Table of Contents (14) Chapters Close

Preface 1. Chapter 1: First Steps 2. Chapter 2: Exploring the Database FREE CHAPTER 3. Chapter 3: Server Configuration 4. Chapter 4: Server Control 5. Chapter 5: Tables and Data 6. Chapter 6: Security 7. Chapter 7: Database Administration 8. Chapter 8: Monitoring and Diagnosis 9. Chapter 9: Regular Maintenance 10. Chapter 10: Performance and Concurrency 11. Chapter 11: Backup and Recovery 12. Chapter 12: Replication and Upgrades 13. Other Books You May Enjoy

Which are my biggest tables?

We've looked at getting the size of a specific table, so now it's time to widen the problem to related areas. Rather than having an absolute value for a specific table, let's look at the relative sizes.

How to do it...

The following basic query will tell us the 10 biggest tables:

SELECT quote_ident(table_schema)||'.'||quote_ident(table_name) as name 
      ,pg_relation_size(quote_ident(table_schema)
              || '.' || quote_ident(table_name)) as size
FROM information_schema.tables
WHERE table_schema NOT IN ('information_schema', 'pg_catalog')
ORDER BY size DESC
LIMIT 10;

The tables are shown in descending order of size, with at the most 10 rows displayed. In this case, we look at all the tables in all the schemas, apart from the tables in information_schema or pg_catalog, as we did in the How many tables are in the database? recipe.

How it works…

PostgreSQL provides a dedicated function, pg_relation_size, to compute the actual disk space used by a specific table or index. We just need to provide the table name. In addition to the main data files, there are other files (called forks) that can be measured by specifying an optional second argument. These include the Visibility Map (VM), the Free Space Map (FSM), and the initialization fork for unlogged objects.

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PostgreSQL 14 Administration Cookbook
Published in: Mar 2022
Publisher: Packt
ISBN-13: 9781803248974
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