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

Visibility


Sometimes your trigger functions may run into the Multiversion Concurrency Control (MVCC) visibility rules of how PostgreSQL's system interacts with changes to data.

A function declared STABLE or IMMUTABLE will never see changes applied to the underlying table by previous triggers.

A VOLATILE function follows more complex rules, which are in a nutshell as follows:

  • The statement-level BEFORE triggers see no changes made by the current statement, and statement-level AFTER triggers see all of the changes made by the statement.

  • Data changes by the operation to the row causing the trigger to fire are of course not visible to BEFORE triggers, as the operation has not happened yet. Changes made by other triggers to other rows in the same statement are visible and as the order of the rows processed is undefined this needs caution!

  • The same is true of INSTEAD OF triggers. The changes by the triggers fired in the same command on previous rows are visible to current invocation of trigger function...