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Mastering PostgreSQL 12 - Third Edition
book

Mastering PostgreSQL 12 - Third Edition

by Hans-Jürgen Schönig
November 2019
Beginner to intermediate content levelBeginner to intermediate
470 pages
11h 59m
English
Packt Publishing
Content preview from Mastering PostgreSQL 12 - Third Edition

Improving speed using clustered tables

In this section, you will learn about the power of correlation and the power of clustered tables. What is this about? Imagine that you want to read a whole area of data. This might be a certain time range, some block, IDs, and so on.

The runtime of these queries will vary, depending on the amount of data and the physical arrangement of data on the disk. So, even if you are running queries that return the same number of rows, two systems might not provide the answer within the same time span, as the physical disk layout might make a difference.

Here is an example:

test=# EXPLAIN (analyze true, buffers true, timing true)       SELECT *    FROM   t_test 
   WHERE  id < 10000;                        QUERY PLAN---------------------------------------------------------- ...
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Publisher Resources

ISBN: 9781838988821Supplemental Content