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<!--
doc/src/sgml/ref/create_extension.sgml
PostgreSQL documentation
-->
<refentry id="SQL-CREATEEXTENSION">
<refmeta>
<refentrytitle>CREATE EXTENSION</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>CREATE EXTENSION</refname>
<refpurpose>install an extension</refpurpose>
</refnamediv>
<indexterm zone="sql-createextension">
<primary>CREATE EXTENSION</primary>
</indexterm>
<refsynopsisdiv>
<synopsis>
CREATE EXTENSION [ IF NOT EXISTS ] <replaceable class="parameter">extension_name</replaceable>
[ WITH ] [ SCHEMA <replaceable class="parameter">schema</replaceable> ]
[ VERSION <replaceable class="parameter">version</replaceable> ]
[ FROM <replaceable class="parameter">old_version</replaceable> ]
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>CREATE EXTENSION</command> loads a new extension into the current
database. There must not be an extension of the same name already loaded.
</para>
<para>
Loading an extension essentially amounts to running the extension's script
file. The script will typically create new <acronym>SQL</> objects such as
functions, data types, operators and index support methods.
<command>CREATE EXTENSION</command> additionally records the identities
of all the created objects, so that they can be dropped again if
<command>DROP EXTENSION</command> is issued.
</para>
<para>
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 <command>CREATE EXTENSION</command> 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.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><literal>IF NOT EXISTS</></term>
<listitem>
<para>
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.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">extension_name</replaceable></term>
<listitem>
<para>
The name of the extension to be
installed. <productname>PostgreSQL</productname> will create the
extension using details from the file
<literal>SHAREDIR/extension/</literal><replaceable class="parameter">extension_name</replaceable><literal>.control</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">schema</replaceable></term>
<listitem>
<para>
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.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">version</replaceable></term>
<listitem>
<para>
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.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">old_version</replaceable></term>
<listitem>
<para><literal>FROM</> <replaceable class="parameter">old_version</>
must be specified when, and only when, you are attempting to install
an extension that replaces an <quote>old style</> module that is just
a collection of objects not packaged into an extension. This option
causes <command>CREATE EXTENSION</> to run an alternative installation
script that absorbs the existing objects into the extension, instead
of creating new objects. Be careful that <literal>SCHEMA</> specifies
the schema containing these pre-existing objects.
</para>
<para>
The value to use for <replaceable
class="parameter">old_version</replaceable> 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
<productname>PostgreSQL</productname>, use <literal>unpackaged</>
for <replaceable class="parameter">old_version</replaceable> when
updating a module to extension style.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
Before you can use <command>CREATE EXTENSION</> to load an extension
into a database, the extension's supporting files must be installed.
Information about installing the extensions supplied with
<productname>PostgreSQL</productname> can be found in
<link linkend="contrib">Additional Supplied Modules</link>.
</para>
<para>
The extensions currently available for loading can be identified from the
<link linkend="view-pg-available-extensions"><structname>pg_available_extensions</structname></link>
or
<link linkend="view-pg-available-extension-versions"><structname>pg_available_extension_versions</structname></link>
system views.
</para>
<para>
For information about writing new extensions, see
<xref linkend="extend-extensions">.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Install the <link linkend="hstore">hstore</link> extension into the
current database:
<programlisting>
CREATE EXTENSION hstore;
</programlisting>
</para>
<para>
Update a pre-9.1 installation of <literal>hstore</> into
extension style:
<programlisting>
CREATE EXTENSION hstore SCHEMA public FROM unpackaged;
</programlisting>
Be careful to specify the schema in which you installed the existing
<literal>hstore</> objects.
</para>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para>
<command>CREATE EXTENSION</command> is a <productname>PostgreSQL</>
extension.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-alterextension"></member>
<member><xref linkend="sql-dropextension"></member>
</simplelist>
</refsect1>
</refentry>
|
