Book Image

Learn PostgreSQL - Second Edition

By : Luca Ferrari, Enrico Pirozzi
1 (2)
Book Image

Learn PostgreSQL - Second Edition

1 (2)
By: Luca Ferrari, Enrico Pirozzi

Overview of this book

The latest edition of this PostgreSQL book will help you to start using PostgreSQL from absolute scratch, helping you to quickly understand the internal workings of the database. With a structured approach and practical examples, go on a journey that covers the basics, from SQL statements and how to run server-side programs, to configuring, managing, securing, and optimizing database performance. This new edition will not only help you get to grips with all the recent changes within the PostgreSQL ecosystem but will also dig deeper into concepts like partitioning and replication with a fresh set of examples. The book is also equipped with Docker images for each chapter which makes the learning experience faster and easier. Starting with the absolute basics of databases, the book sails through to advanced concepts like window functions, logging, auditing, extending the database, configuration, partitioning, and replication. It will also help you seamlessly migrate your existing database system to PostgreSQL and contains a dedicated chapter on disaster recovery. Each chapter ends with practice questions to test your learning at regular intervals. By the end of this book, you will be able to install, configure, manage, and develop applications against a PostgreSQL database.
Table of Contents (22 chapters)
20
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21
Index

ANALYZE and how to update statistics

PostgreSQL exploits a statistical approach to evaluate different execution plans. This means that PostgreSQL does not know how many tuples there are in a table, but has a good approximation that allows the planner to compute the cost of the execution plan.

Statistics are not only related to the quantity (how many tuples) but also to the quality of the underlying data – for example, how many distinct values there are, which values are more frequent in a column, and so on. Thanks to the combination of all of this data, PostgreSQL is able to make a performant decision.

There are times, however, when the quality of the statistical data is not good enough for PostgreSQL to choose the best plan, a problem commonly known as “out-of-date statistics.” In fact, statistics are not updated in real time; rather, PostgreSQL keeps track of what is ongoing in every table in every database and summarizes the number of new tuples, updated...