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|CREATE EXTENSION(7)||PostgreSQL 11.9 Documentation||CREATE EXTENSION(7)|
NAME¶CREATE_EXTENSION - install an extension
CREATE EXTENSION [ IF NOT EXISTS ] extension_name [ WITH ] [ SCHEMA schema_name ] [ VERSION version ] [ FROM old_version ] [ CASCADE ]
DESCRIPTION¶CREATE EXTENSION loads a new extension into the current database. There must not be an extension of the same name already loaded.
Loading an extension essentially amounts to running the extension's script file. The script will typically create new SQL objects such as functions, data types, operators and index support methods. CREATE EXTENSION additionally records the identities of all the created objects, so that they can be dropped again if DROP EXTENSION is issued.
Loading an extension requires the same privileges that would be required to create its component objects. For most extensions this means superuser or database owner privileges are needed. The user who runs CREATE EXTENSION becomes the owner of the extension for purposes of later privilege checks, as well as the owner of any objects created by the extension's script.
PARAMETERS¶IF NOT EXISTS
If the extension specifies a schema parameter in its control file, then that schema cannot be overridden with a SCHEMA clause. Normally, an error will be raised if a SCHEMA clause is given and it conflicts with the extension's schema parameter. However, if the CASCADE clause is also given, then schema_name is ignored when it conflicts. The given schema_name will be used for installation of any needed extensions that do not specify schema in their control files.
Remember that the extension itself is not considered to be within any schema: extensions have unqualified names that must be unique database-wide. But objects belonging to the extension can be within schemas.
The value to use for old_version is determined by the extension's author, and might vary if there is more than one version of the old-style module that can be upgraded into an extension. For the standard additional modules supplied with pre-9.1 PostgreSQL, use unpackaged for old_version when updating a module to extension style.
NOTES¶Before you can use CREATE EXTENSION to load an extension into a database, the extension's supporting files must be installed. Information about installing the extensions supplied with PostgreSQL can be found in Additional Supplied Modules.
The extensions currently available for loading can be identified from the pg_available_extensions or pg_available_extension_versions system views.
Installing an extension as superuser requires trusting that the extension's author wrote the extension installation script in a secure fashion. It is not terribly difficult for a malicious user to create trojan-horse objects that will compromise later execution of a carelessly-written extension script, allowing that user to acquire superuser privileges. However, trojan-horse objects are only hazardous if they are in the search_path during script execution, meaning that they are in the extension's installation target schema or in the schema of some extension it depends on. Therefore, a good rule of thumb when dealing with extensions whose scripts have not been carefully vetted is to install them only into schemas for which CREATE privilege has not been and will not be granted to any untrusted users. Likewise for any extensions they depend on.
The extensions supplied with PostgreSQL are believed to be secure against installation-time attacks of this sort, except for a few that depend on other extensions. As stated in the documentation for those extensions, they should be installed into secure schemas, or installed into the same schemas as the extensions they depend on, or both.
For information about writing new extensions, see Section 38.16.
EXAMPLES¶Install the hstore extension into the current database, placing its objects in schema addons:
CREATE EXTENSION hstore SCHEMA addons;
Another way to accomplish the same thing:
SET search_path = addons; CREATE EXTENSION hstore;
Update a pre-9.1 installation of hstore into extension style:
CREATE EXTENSION hstore SCHEMA public FROM unpackaged;
Be careful to specify the schema in which you installed the existing hstore objects.
COMPATIBILITY¶CREATE EXTENSION is a PostgreSQL extension.
SEE ALSO¶ALTER EXTENSION (ALTER_EXTENSION(7)), DROP EXTENSION (DROP_EXTENSION(7))