Book Image

PostgreSQL Development Essentials

By : Baji Shaik
Book Image

PostgreSQL Development Essentials

By: Baji Shaik

Overview of this book

PostgreSQL is the most advanced open source database in the world. It is easy to install, configure, and maintain by following the documentation; however, it’s difficult to develop applications using programming languages and design databases accordingly. This book is what you need to get the most out of PostgreSQL You will begin with advanced SQL topics such as views, materialized views, and cursors, and learn about performing data type conversions. You will then perform trigger operations and use trigger functions in PostgreSQL. Next we walk through data modeling, normalization concepts, and the effect of transactions and locking on the database. The next half of the book covers the types of indexes, constrains, and the concepts of table partitioning, as well as the different mechanisms and approaches available to write efficient queries or code. Later, we explore PostgreSQL Extensions and Large Object Support in PostgreSQL. Finally, you will perform database operations in PostgreSQL using PHP and Java. By the end of this book, you will have mastered all the aspects of PostgreSQL development. You will be able to build efficient enterprise-grade applications with PostgreSQL by making use of these concepts
Table of Contents (17 chapters)
PostgreSQL Development Essentials
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface

Bad query performance with stale statistics


Query performance always depends on the plan chosen by the Optimizer. Optimizer again depends on the statistics of corresponding relations to generate a plan for the query. If Postgres has stale statistics, the query might get bad plans irrespective of the existing datasets.

For example, consider we have the following two test tables on which we perform basic operations like the following:

CREATE TABLE out(t INTEGER);
CREATE TABLE inn(t INTEGER);
postgres=# SELECT COUNT(*) FROM out;
count 
-------
1000
(1 row)
postgres=# SELECT COUNT(*) FROM inn;
count 
-------
1000
(1 row)
postgres=# EXPLAIN ANALYZE SELECT * FROM out WHERE t IN(SELECT t  FROM inn);
                       QUERY PLAN
----------------------------------------------------------------               
Hash Semi Join  (cost=27.50..56.25 rows=1000 width=4) (actual  time=1.201..3.646 rows=1000 loops=1)
Hash Cond: ("out".t = inn.t)
-> Seq Scan on "out"  (cost=0.00..15.00 rows=1000...