Book Image

PostgreSQL Server Programming

Book Image

PostgreSQL Server Programming

Overview of this book

Learn how to work with PostgreSQL as if you spent the last decade working on it. PostgreSQL is capable of providing you with all of the options that you have in your favourite development language and then extending that right on to the database server. With this knowledge in hand, you will be able to respond to the current demand for advanced PostgreSQL skills in a lucrative and booming market."PostgreSQL Server Programming" will show you that PostgreSQL is so much more than a database server. In fact, it could even be seen as an application development framework, with the added bonuses of transaction support, massive data storage, journaling, recovery and a host of other features that the PostgreSQL engine provides. This book will take you from learning the basic parts of a PostgreSQL function, then writing them in languages other than the built-in PL/PgSQL. You will see how to create libraries of useful code, group them into even more useful components, and distribute them to the community. You will see how to extract data from a multitude of foreign data sources, and then extend PostgreSQL to do it natively. And you can do all of this in a nifty debugging interface that will allow you to do it efficiently and with reliability.
Table of Contents (17 chapters)
PostgreSQL Server Programming
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Summary


A trigger is a binding of a set of actions to certain operations performed on a table or view. This set of actions is defined in a special trigger function distinguished by specifying the type of returned value to be of special pseudotype trigger. So each time an operation (INSERT, UPDATE, DELETE, or TRUNCATE) is performed on the table, this trigger function is called by the system.

It can be executed either FOR EACH ROW or FOR EACH STATEMENT. If executed for each row (row level trigger), the function is passed special variables OLD and NEW. This will contain the row content, as it is currently in the database (OLD), and as it is at the moment the trigger function is called (NEW). Where the OLD or NEW value is missing, it is passed as undefined. If executed once per statement (the statement-level trigger), both OLD and NEW are unassigned for all operations.

The trigger function for row-level triggers on INSERT, UPDATE, and DELETE can be set to execute either BEFORE or AFTER the operation...