NAME

       CREATE_LANGUAGE - define a new procedural language

SYNOPSIS

       CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
           HANDLER call_handler [ INLINE inline_handler ] [ VALIDATOR valfunction ]
       CREATE [ OR REPLACE ] [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name

DESCRIPTION

       CREATE LANGUAGE registers a new procedural language with a PostgreSQL database.
       Subsequently, functions and procedures can be defined in this new language.

       CREATE LANGUAGE effectively associates the language name with handler function(s) that are
       responsible for executing functions written in the language. Refer to Chapter 56 for more
       information about language handlers.

       CREATE OR REPLACE LANGUAGE will either create a new language, or replace an existing
       definition. If the language already exists, its parameters are updated according to the
       command, but the language's ownership and permissions settings do not change, and any
       existing functions written in the language are assumed to still be valid.

       One must have the PostgreSQL superuser privilege to register a new language or change an
       existing language's parameters. However, once the language is created it is valid to
       assign ownership of it to a non-superuser, who may then drop it, change its permissions,
       rename it, or assign it to a new owner. (Do not, however, assign ownership of the
       underlying C functions to a non-superuser; that would create a privilege escalation path
       for that user.)

       The form of CREATE LANGUAGE that does not supply any handler function is obsolete. For
       backwards compatibility with old dump files, it is interpreted as CREATE EXTENSION. That
       will work if the language has been packaged into an extension of the same name, which is
       the conventional way to set up procedural languages.

PARAMETERS

       TRUSTED
           TRUSTED specifies that the language does not grant access to data that the user would
           not otherwise have. 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 name must be unique among the languages
           in the database.

       HANDLER call_handler
           call_handler is the name of a previously registered function that will be called to
           execute the procedural language's 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.

       INLINE inline_handler
           inline_handler is the name of a previously registered function that will be called to
           execute an anonymous code block (DO command) in this language. If no inline_handler
           function is specified, the language does not support anonymous code blocks. The
           handler function must take one argument of type internal, which will be the DO
           command's internal representation, and it will typically return void. The return value
           of the handler is ignored.

       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

       Use DROP LANGUAGE to drop procedural languages.

       The system catalog pg_language (see Section 52.29) records information about the currently
       installed languages. Also, the psql command \dL lists 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.

EXAMPLES

       A minimal sequence for creating a new procedural language is:

           CREATE FUNCTION plsample_call_handler() RETURNS language_handler
               AS '$libdir/plsample'
               LANGUAGE C;
           CREATE LANGUAGE plsample
               HANDLER plsample_call_handler;

       Typically that would be written in an extension's creation script, and users would do this
       to install the extension:

           CREATE EXTENSION plsample;

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(7), REVOKE(7)