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. The user must have the
PostgreSQL superuser privilege to
register a 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 the
Programmer's Guide for more information
about language call handlers.
Note that procedural languages are local to individual databases.
To make a language available in all databases by default, it should
be installed into the template1 database.
Notes
This command normally should not be executed directly by users.
For the procedural languages supplied in the
PostgreSQL distribution, the createlang script should be used, which will also
install the correct call handler. (createlang
will call CREATE LANGUAGE internally.)
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.
Use the CREATE FUNCTION command to create a new
function.
Use DROP LANGUAGE, or better yet the droplang script, to drop procedural languages.
The system catalog pg_language records
information about the currently installed procedural languages.
Table "pg_language"
Attribute | Type | Modifier
---------------+-----------+----------
lanname | name |
lanispl | boolean |
lanpltrusted | boolean |
lanplcallfoid | oid |
lanvalidator | oid |
lanacl | aclitem[] |
lanname | lanispl | lanpltrusted | lanplcallfoid | lanvalidator | lanacl
-------------+---------+--------------+---------------+--------------+--------
internal | f | f | 0 | 2246 |
c | f | f | 0 | 2247 |
sql | f | t | 0 | 2248 | {=U}
At present, with the exception of the permissions, the definition
of a procedural language cannot be changed once it has been created.
To be able to use a procedural language, a user must be granted the
USAGE privilege. The
createlang program automatically grants
permissions to everyone if the language is known to be trusted.
Examples
The following two commands executed in sequence will register a new
procedural language and the associated call handler.
CREATE FUNCTION plsample_call_handler () RETURNS language_handler
AS '$libdir/plsample'
LANGUAGE C;
CREATE LANGUAGE plsample
HANDLER plsample_call_handler;
