Provided by: postgresql-client-8.4_8.4.11-1_amd64 bug

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       behavior simplifies loading of old dump files, which are  likely  to  contain  out-of-date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 database 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 registered 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_pltemplate.

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 language_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)]