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CREATE LANGUAGE(7) PostgreSQL 14.15 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 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The form of CREATE LANGUAGE that does not supply any handler function is obsolete.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)
PostgreSQL 14.15 2024 CREATE LANGUAGE(7)
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