Book Image

PostgreSQL 11 Administration Cookbook

By : Simon Riggs, Gianni Ciolli, Sudheer Kumar Meesala
Book Image

PostgreSQL 11 Administration Cookbook

By: Simon Riggs, Gianni Ciolli, Sudheer Kumar Meesala

Overview of this book

PostgreSQL is a powerful, open source database management system with an enviable reputation for high performance and stability. With many new features in its arsenal, PostgreSQL 11 allows you to scale up your PostgreSQL infrastructure. This book takes a step-by-step, recipe-based approach to effective PostgreSQL administration. The book will introduce you to new features such as logical replication, native table partitioning, additional query parallelism, and much more to help you to understand and control, crash recovery and plan backups. You will learn how to tackle a variety of problems and pain points for any database administrator such as creating tables, managing views, improving performance, and securing your database. As you make steady progress, the book will draw attention to important topics such as monitoring roles, backup, and recovery of your PostgreSQL 11 database to help you understand roles and produce a summary of log files, ensuring high availability, concurrency, and replication. By the end of this book, you will have the necessary knowledge to manage your PostgreSQL 11 database efficiently.
Table of Contents (19 chapters)
Title Page
Copyright and Credits
About Packt

Adding a constraint without checking existing rows

A table constraint is a guarantee that must be satisfied by all of the rows in the table. Therefore, adding a constraint to a table is a two-phase procedure—first, the constraint is created, and then all of the existing rows are checked. Both happen in the same transaction, and the table cannot be accessed in the meantime. The constraint becomes visible after the check, yielding perfect consistency, which is usually the desired behavior, but it's at the expense of availability, which is not that great.

This recipe demonstrates another case—how to enforce a constraint on future transactions only, without checking existing rows. This may be desirable in some specific cases, such as the following:

  • Enabling the constraint on newer rows of a large table that cannot remain unavailable for a long time
  • Enforcing the constraint on newer rows, while keeping older rows that are known to violate the constraint

The constraint is marked as NOT VALID to make...