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       CREATE LANGUAGE - define a new procedural language


           HANDLER call_handler [ VALIDATOR valfunction ]


       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       dump  files,  which are likely to contain out-of-date information about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.


              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.

              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

       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.


       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

       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

       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


       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;


       CREATE LANGUAGE is a PostgreSQL extension.


       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