You're reading from Learn PostgreSQL - Second Edition

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Published inOct 2023

PublisherPackt

ISBN-139781837635641

Edition2nd Edition

Concepts

Data Analysis

Authors (2):

Luca Ferrari

Enrico Pirozzi

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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quality of the statistical data is not good enough for PostgreSQL to choose the best plan, a problem commonly known as “out-of-date statistics.”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...

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Learn PostgreSQL - Second Edition

Published in: Oct 2023Publisher: PacktISBN-13: 9781837635641

Authors (2)

Luca Ferrari

Luca Ferrari has been passionate about computer science since the Commodore 64 era, and today holds a master's degree (with honors) and a Ph.D. from the University of Modena and Reggio Emilia. He has written several research papers, technical articles, and book chapters. In 2011, he was named an Adjunct Professor by Nipissing University. An avid Unix user, he is a strong advocate of open source, and in his free time, he collaborates with a few projects. He met PostgreSQL back in release 7.3; he was a founder and former president of the Italian PostgreSQL Community (ITPUG). He also talks regularly at technical conferences and events and delivers professional training.
Read more about Luca Ferrari

Enrico Pirozzi

Enrico Pirozzi, EnterpriseDB certified on implementation management and tuning, with a master's in computer science, has been a PostgreSQL DBA since 2003. Based in Italy, he has been providing database advice to clients in industries such as manufacturing and web development for 10 years. He has been training others on PostgreSQL since 2008. Dedicated to open source technology since early in his career, he is a cofounder of the PostgreSQL Italian mailing list, PostgreSQL-it, and of the PostgreSQL Italian community site, PSQL
Read more about Enrico Pirozzi

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