CREATE 
LANGUAGE(7)						   SQL Commands 						CREATE LANGUAGE(7)

NAME

       CREATE LANGUAGE - define a new procedural language

SYNOPSIS

       CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE langname
	   HANDLER call_handler [ VALIDATOR valfunction ]

DESCRIPTION

       Using  CREATE  LANGUAGE,  a  PostgreSQL user can register a new procedural language with a PostgreSQL database. Subsequently, functions and
       trigger procedures can be defined in this new language. The user must have the PostgreSQL superuser privilege to register a new language.

       CREATE LANGUAGE effectively associates the language name with a call handler that is responsible for executing  functions  written  in  the
       language. Refer to the Programmer's Guide for more information about language call handlers.

       Note  that  procedural languages are local to individual databases.  To make a language available in all databases by default, it should be
       installed into the template1 database.

PARAMETERS

       TRUSTED
	      TRUSTED specifies that the call handler for the language is safe, that is, it does not offer an unprivileged user any  functionality
	      to  bypass  access  restrictions. If this keyword is omitted when registering the language, only users with the PostgreSQL superuser
	      privilege can use this language to create new functions.

       PROCEDURAL
	      This is a noise word.

       langname
	      The name of the new procedural language. The language name is case insensitive. A procedural language cannot  override  one  of  the
	      built-in languages of PostgreSQL.

	      For backward compatibility, the name may be enclosed by single quotes.

       HANDLER call_handler
	      call_handler  is	the name of a previously registered function that will be called to execute the procedural language functions. The
	      call handler for a procedural language must be written in a compiled language such as C with version 1 call  convention  and  regis-
	      tered  with  PostgreSQL as a function taking no arguments and returning the language_handler type, a placeholder type that is simply
	      used to identify the function as a call handler.

       VALIDATOR valfunction
	      valfunction is the name of a previously registered function that will be called when a new function in the language is  created,	to
	      validate	the new function.  If no validator function is specified, then a new function will not be checked when it is created.  The
	      validator function must take one argument of type oid, which will be the OID of  the  to-be-created  function,  and  will  typically
	      return void.

	      A validator function would typically inspect the function body for syntactical correctness, but it can also look at other properties
	      of the function, for example if the language cannot handle certain argument types. To signal an error, the validator function should
	      use the elog() function. The return value of the function is ignored.

DIAGNOSTICS

       CREATE LANGUAGE

       This message is returned if the language is successfully created.

       ERROR:  PL handler function funcname() doesn't exist

       This error is returned if the function funcname() is not found.

NOTES

       This  command normally should not be executed directly by users.  For the procedural languages supplied in the PostgreSQL distribution, the
       createlang(1) script should be used, which will also install the correct call handler. (createlang will call CREATE LANGUAGE internally.)

       In PostgreSQL versions before 7.3, it was necessary to declare handler functions as returning the placeholder type opaque, rather than lan-
       guage_handler.	To  support  loading  of  old dump files, CREATE LANGUAGE will accept a function declared as returning opaque, but it will
       issue a NOTICE and change the function's declared return type to language_handler.

       Use the CREATE FUNCTION [create_function(7)] command to create a new function.

       Use DROP LANGUAGE [drop_language(7)], or better yet the droplang(1) script, to drop procedural languages.

       The system catalog pg_language records information about the currently installed procedural languages.

	       Table "pg_language"
	  Attribute   |   Type	  | Modifier
       ---------------+-----------+----------
	lanname       | name	  |
	lanispl       | boolean   |
	lanpltrusted  | boolean   |
	lanplcallfoid | oid	  |
	lanvalidator  | oid	  |
	lanacl	      | aclitem[] |

	  lanname   | lanispl | lanpltrusted | lanplcallfoid | lanvalidator | lanacl
       -------------+---------+--------------+---------------+--------------+--------
	internal    | f       | f	     |		   0 |	       2246 |
	c	    | f       | f	     |		   0 |	       2247 |
	sql	    | f       | t	     |		   0 |	       2248 | {=U}

       At present, with the exception of the permissions, the definition of a procedural language cannot be changed once it has been created.

       To be able to use a procedural language, a user must be granted the USAGE privilege. The createlang program  automatically  grants  permis-
       sions to everyone if the language is known to be trusted.

EXAMPLES

       The following two commands executed in sequence will register a new procedural language and the associated call handler.

       CREATE FUNCTION plsample_call_handler () RETURNS language_handler
	   AS '$libdir/plsample'
	   LANGUAGE C;
       CREATE LANGUAGE plsample
	   HANDLER plsample_call_handler;

COMPATIBILITY

       CREATE LANGUAGE is a PostgreSQL extension.

HISTORY

       The CREATE LANGUAGE command first appeared in PostgreSQL 6.3.

SEE ALSO

       createlang(1),  CREATE  FUNCTION [create_function(7)], droplang(1), DROP LANGUAGE [drop_language(l)], GRANT [grant(l)], REVOKE [revoke(l)],
       PostgreSQL Programmer's Guide

SQL - Language Statements					    2002-11-22							CREATE LANGUAGE(7)