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NAME

       CREATE LANGUAGE - define a new procedural language

SYNOPSIS

       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. 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  documentation  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 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 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  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.

NOTES

       This  command  normally  should not be executed directly by users.  For
       the procedural languages supplied in the PostgreSQL  distribution,  the
       createlang(1)  program  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
       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.

       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)
       program, to drop procedural languages.

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

       To be able to use a procedural language, a user  must  be  granted  the
       USAGE   privilege.   The   createlang   program   automatically  grants
       permissions 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.

SEE ALSO

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