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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 han-
       dlers.

       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 consid-
       ered obsolescent.

       When the server finds an entry in the pg_pltemplate catalog for the given language name, it will use the  cata-
       log  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       which are likely to contain out-of-date information about language support functions.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_pltem-
       plate 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 unprivi-
              leged 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 procedu-
              ral language functions. The call handler for a procedural language must be written in  a  compiled  lan-
              guage  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 argu-
              ment 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 pro-
       cedural 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 tem-
       plate1 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)]



SQL - Language Statements         2014-02-17                CREATE LANGUAGE(7)