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

NAME

       CREATE LANGUAGE - define a new procedural language

SYNOPSIS

       CREATE [ PROCEDURAL ] LANGUAGE name
       CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
	   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.

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

       There  are  two	forms of the CREATE LANGUAGE command.  In the first form, the user supplies just the name of the desired language, and the
       PostgreSQL server consults the pg_pltemplate system catalog to determine the correct parameters. In the second form, the user supplies  the
       language  parameters  along with the language name.  The second form can be used to create a language that is not defined in pg_pltemplate,
       but this approach is considered obsolescent.

       When the server finds an entry in the pg_pltemplate catalog for the given language name, it will use the catalog data even if  the  command
       includes language parameters. This behavior simplifies loading of old dump files, which are likely to contain out-of-date information about
       language support functions.

       Ordinarily, the user must have the PostgreSQL superuser privilege to register a new language. However, the owner of a database can register
       a  new language within that database if the language is listed in the pg_pltemplate catalog and is marked as allowed to be created by data-
       base owners (tmpldbacreate is true). The default is that trusted languages can be created by database owners, but this can be  adjusted	by
       superusers  by  modifying  the contents of pg_pltemplate.  The creator of a language becomes its owner and can later drop it, rename it, or
       assign it to a new owner.

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 key word 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.

       name   The name of the new procedural language. The language name is case insensitive. The name must be unique among the languages  in  the
	      database.

	      For backward compatibility, the name can 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 ereport() function. The return value of the function is ignored.

       The  TRUSTED  option  and  the support function name(s) are ignored if the server has an entry for the specified language name in pg_pltem-
       plate.

NOTES

       The createlang(1) program is a simple wrapper around the CREATE LANGUAGE command. It eases installation of procedural  languages  from  the
       shell command line.

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

       The system catalog pg_language (see in the documentation) records information about the currently installed languages. Also, createlang has
       an option to list the installed languages.

       To create functions in a procedural language, a user must have the USAGE privilege for the language. By default, USAGE is granted to PUBLIC
       (i.e., everyone) for trusted languages. This can be revoked if desired.

       Procedural languages are local to individual databases.	However, a language can be installed into the template1 database, which will cause
       it to be available automatically in all subsequently-created databases.

       The call handler function and the validator function (if any) must already exist if the server does not have an entry for the  language	in
       pg_pltemplate.  But  when there is an entry, the functions need not already exist; they will be automatically defined if not present in the
       database.  (This might result in CREATE LANGUAGE failing, if the shared library that implements	the  language  is  not	available  in  the
       installation.)

       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.

EXAMPLES

       The preferred way of creating any of the standard procedural languages is just:

       CREATE LANGUAGE plpgsql;

       For a language not known in the pg_pltemplate catalog, a sequence such as this is needed:

       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.

SEE ALSO

       ALTER  LANGUAGE	[alter_language(7)],  CREATE  FUNCTION	[create_function(7)],  DROP  LANGUAGE [drop_language(7)], GRANT [grant(7)], REVOKE
       [revoke(7)], createlang [createlang(1)], droplang [droplang(1)]

SQL - Language Statements					    2010-05-14							CREATE LANGUAGE(7)