NAME

       CREATE_EXTENSION - install an extension

SYNOPSIS

       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
           Do not throw an error if an extension with the same name already exists. A notice is
           issued in this case. Note that there is no guarantee that the existing extension is
           anything like the one that would have been created from the currently-available script
           file.

       extension_name
           The name of the extension to be installed.  PostgreSQL will create the extension using
           details from the file SHAREDIR/extension/extension_name.control.

       schema_name
           The name of the schema in which to install the extension's objects, given that the
           extension allows its contents to be relocated. The named schema must already exist. If
           not specified, and the extension's control file does not specify a schema either, the
           current default object creation schema is used.

           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.

       version
           The version of the extension to install. This can be written as either an identifier
           or a string literal. The default version is whatever is specified in the extension's
           control file.

       old_version
           FROM old_version must be specified when, and only when, you are attempting to install
           an extension that replaces an “old style” module that is just a collection of objects
           not packaged into an extension. This option causes CREATE EXTENSION to run an
           alternative installation script that absorbs the existing objects into the extension,
           instead of creating new objects. Be careful that SCHEMA specifies the schema
           containing these pre-existing objects.

           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.

       CASCADE
           Automatically install any extensions that this extension depends on that are not
           already installed. Their dependencies are likewise automatically installed,
           recursively. The SCHEMA clause, if given, applies to all extensions that get installed
           this way. Other options of the statement are not applied to automatically-installed
           extensions; in particular, their default versions are always selected.

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.

           Caution
           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 37.15.

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))