<chapter id="dfunc">

<title id="dfunc-title">Linking Dynamically-Loaded Functions</title>

<para>

<!--

.SH "Compiling Dynamically-Loaded C Functions"

.PP

procedure.

-->

<para>

After you have created and registered a user-defined

function, your work is essentially done. <productname>Postgres</productname>,

however, must load the object code (e.g., a <filename>.o</filename> file, or

function, your work is essentially done.

<productname>Postgres</productname>,

however, must load the object code

(e.g., a <literal>.o</literal> file, or

a shared library) that implements your function. As

previously mentioned, <productname>Postgres</productname> loads your code at

previously mentioned, <productname>Postgres</productname>

loads your code at

runtime, as required. In order to allow your code to be

dynamically loaded, you may have to compile and

link-edit it in a special way. This section briefly

describes how to perform the compilation and

link-editing required before you can load your user-defined

functions into a running <productname>Postgres</productname> server. Note that

functions into a running <productname>Postgres</productname> server.

Note that

this process has changed as of Version 4.2.

</para>

<!--

<tip>

and alignment of executable instructions within memory, etc.

on the part of the person writing the dynamic loader. Such

loaders tended to be slow and buggy. As of Version 4.2, the

<productname>Postgres</productname> dynamic loading mechanism has been rewritten to use

<productname>Postgres</productname> dynamic loading mechanism

has been rewritten to use

the dynamic loading mechanism provided by the operating

system. This approach is generally faster, more reliable and

more portable than our previous dynamic loading mechanism.

The reason for this is that nearly all modern versions of

Unix use a dynamic loading mechanism to implement shared

libraries and must therefore provide a fast and reliable

mechanism. On the other hand, the object file must be

postprocessed a bit before it can be loaded into <productname>Postgres</productname>. We

postprocessed a bit before it can be loaded into

<productname>Postgres</productname>. We

hope that the large increase in speed and reliability will

make up for the slight decrease in convenience.

</para>