CREATE LANGUAGE(7) PostgreSQL 15.7 Documentation CREATE LANGUAGE(7)
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 58 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is obsolete.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 53.29) 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)
PostgreSQL 15.7 2024 CREATE LANGUAGE(7)
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