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

Adding functionality to add(int, int)


While our function works, it adds nothing in the preceding code just using SELECT A + B, but functions written in C are capable of so much more. Let's start adding some more functionality to our function.

Smart handling of NULL arguments

Notice the use of STRICT keyword in the CREATE FUNCTION add(int a, int b) in the previously mentioned code. This means that the function will not be called if any of the arguments are NULL, but instead NULL is returned straight away. This is similar to how most PostgreSQL operators works, including the + sign when adding two integers—if any of the arguments are NULL the complete result is NULL as well.

Next, we will extend our function to be smarter about NULL inputs and act like PostgreSQL's sum() aggregate function, which ignores NULL values in inputs and still produces sum of all non-null values.

For this, we need to do two things:

  1. Make sure that the function is called when either of the arguments are NULL.

  2. Handle NULL...