<SYNOPSIS>

CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">ftype</replaceable> [, ...] ] )

RETURNS <replaceable class="parameter">rtype</replaceable>

AS <replaceable class="parameter">path</replaceable>

AS <replaceable class="parameter">definition</replaceable>

LANGUAGE '<replaceable class="parameter">langname</replaceable>'

</SYNOPSIS>

</VARLISTENTRY>

<VARLISTENTRY>

<TERM>

<replaceable class="parameter">path</replaceable>

<replaceable class="parameter">definition</replaceable>

</TERM>

<LISTITEM>

<PARA>

May be either an SQL-query or an absolute path to an

object file.

A string defining the function; the meaning depends on the language.

It may be an internal function name, the path to an object file,

an SQL query, or text in a procedural language.

</PARA>

</LISTITEM>

</VARLISTENTRY>

Use <command>DROP FUNCTION</command>

to drop user-defined functions.

</PARA>

<PARA>

<productname>Postgres</productname> allows function "overloading";

that is, the same name can be used for several different functions

so long as they have distinct argument types. This facility must be

used with caution for INTERNAL and C-language functions, however.

</PARA>

<PARA>

Two INTERNAL functions cannot have the same C name without causing

errors at link time. To get around that, give them different C names

(for example, use the argument types as part of the C names), then

specify those names in the AS clause of <command>CREATE FUNCTION</command>.

If the AS clause is left empty then <command>CREATE FUNCTION</command>

assumes the C name of the function is the same as the SQL name.

</PARA>

<PARA>

For dynamically-loaded C functions, the SQL name of the function must

be the same as the C function name, because the AS clause is used to

give the path name of the object file containing the C code. In this

situation it is best not to try to overload SQL function names. It

might work to load a C function that has the same C name as an internal

function or another dynamically-loaded function --- or it might not.

On some platforms the dynamic loader may botch the load in interesting

ways if there is a conflict of C function names. So, even if it works

for you today, you might regret overloading names later when you try

to run the code somewhere else.

</PARA>

</REFSECT2>

</refsect1>