Book Image

Learning PostgreSQL

Book Image

Learning PostgreSQL

Overview of this book

PostgreSQL is one of the most powerful and easy to use database management systems. It supports the most advanced features included in SQL standards. The book starts with the introduction of relational databases with PostegreSQL. It then moves on to covering data definition language (DDL) with emphasis on PostgreSQL and common DDL commands supported by ANSI SQL. You will then learn the data manipulation language (DML), and advanced topics like locking and multi version concurrency control (MVCC). This will give you a very robust background to tune and troubleshoot your application. The book then covers the implementation of data models in the database such as creating tables, setting up integrity constraints, building indexes, defining views and other schema objects. Next, it will give you an overview about the NoSQL capabilities of PostgreSQL along with Hstore, XML, Json and arrays. Finally by the end of the book, you'll learn to use the JDBC driver and manipulate data objects in the Hibernate framework.
Table of Contents (21 chapters)
Learning PostgreSQL
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Cleaning up the database


Often, a database can contain several unused objects or very old data. Cleaning up these objects helps administrators perform a backup of images more quickly. From the development point of view, unused objects are similar to quiet noise because they affect the refactoring process.

Getting ready

In database applications, one needs to keep the database clean as database objects might hinder quick development due to the objects' dependencies. To clean the database, one needs to identify the unused database objects, including tables, views, indexes, and functions.

A recipe for bloated tables and indexes will not be introduced here; you can take a look at the bucardo check_postgres Nagios plugin code at https://bucardo.org/wiki/Check_postgres to understand how bloats in tables and indexes can be calculated.

How to do it…

Table statistics, such as the number of live rows, index scans, and sequential scans, can help identify empty and unused tables. Note that the following queries...