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

Simplest C function – return (a + b)


Let's start with a simple function, which takes two integer arguments and returns the sum of these. We first present the source code and then will move on to show you how to compile it, load it into PostgreSQL, and then use it as any native function.

add_func.c

A C source file implementing add(int, int) returns int function looks like the following code snippet:

#include "postgres.h"
#include "fmgr.h"

PG_MODULE_MAGIC;

PG_FUNCTION_INFO_V1(add_ab);

Datum
add_ab(PG_FUNCTION_ARGS)
{
    int32   arg_a = PG_GETARG_INT32(0);
    int32   arg_b = PG_GETARG_INT32(1);

    PG_RETURN_INT32(arg_a + arg_b);
}

Let's go over the code explaining the use of each segment:

  • #include "postgres.h": This includes most of the basic definitions and declarations needed for writing any C code for running in PostgreSQL.

  • #include "fmgr.h": This includes the definitions for PG_* macros used in this code.

  • PG_MODULE_MAGIC;: This is a "magic block" defined in fmgr.h. This block is used by...