<!-- doc/src/sgml/contrib.sgml -->

<appendix id="contrib">
 <title>Additional Supplied Modules and Extensions</title>

 <para>
  This appendix and the next one contain information on the
  optional components
  found in the <literal>contrib</literal> directory of the
  <productname>PostgreSQL</productname> distribution.
  These include porting tools, analysis utilities,
  and plug-in features that are not part of the core PostgreSQL system.
  They are separate mainly
  because they address a limited audience or are too experimental
  to be part of the main source tree.  This does not preclude their
  usefulness.
 </para>

 <para>
  This appendix covers extensions and other server plug-in module
  libraries found in
  <literal>contrib</literal>.  <xref linkend="contrib-prog"/> covers utility
  programs.
 </para>

 <para>
  When building from the source distribution, these optional
  components are not built
  automatically, unless you build the "world" target
  (see <xref linkend="build"/>).
  You can build and install all of them by running:
<screen>
<userinput>make</userinput>
<userinput>make install</userinput>
</screen>
  in the <literal>contrib</literal> directory of a configured source tree;
  or to build and install
  just one selected module, do the same in that module's subdirectory.
  Many of the modules have regression tests, which can be executed by
  running:
<screen>
<userinput>make check</userinput>
</screen>
  before installation or
<screen>
<userinput>make installcheck</userinput>
</screen>
  once you have a <productname>PostgreSQL</productname> server running.
 </para>

 <para>
  If you are using a pre-packaged version of <productname>PostgreSQL</productname>,
  these components are typically made available as a separate subpackage,
  such as <literal>postgresql-contrib</literal>.
 </para>

 <para>
  Many components supply new user-defined functions, operators, or types,
  packaged as <firstterm>extensions</firstterm>.
  To make use of one of these extensions, after you have installed the code
  you need to register the new SQL objects in the database system.
  This is done by executing
  a <xref linkend="sql-createextension"/> command.  In a fresh database,
  you can simply do

<programlisting>
CREATE EXTENSION <replaceable>extension_name</replaceable>;
</programlisting>

  This command registers the new SQL objects in the current database only,
  so you need to run it in every database in which you want
  the extension's facilities to be available.  Alternatively, run it in
  database <literal>template1</literal> so that the extension will be copied into
  subsequently-created databases by default.
 </para>

 <para>
  For all extensions, the <command>CREATE EXTENSION</command> command must be
  run by a database superuser, unless the extension is
  considered <quote>trusted</quote>.  Trusted extensions can be run by any
  user who has <literal>CREATE</literal> privilege on the current
  database.  Extensions that are trusted are identified as such in the
  sections that follow.  Generally, trusted extensions are ones that cannot
  provide access to outside-the-database functionality.
 </para>

 <para id="contrib-trusted-extensions">
  The following extensions are trusted in a default installation:

  <simplelist type="vert" columns="4">
   <member><xref linkend="btree-gin"/></member>
   <member><xref linkend="btree-gist"/></member>
   <member><xref linkend="citext"/></member>
   <member><xref linkend="cube"/></member>
   <member><xref linkend="dict-int"/></member>
   <member><xref linkend="fuzzystrmatch"/></member>
   <member><xref linkend="hstore"/></member>
   <member><xref linkend="intarray"/></member>
   <member><xref linkend="isn"/></member>
   <member><xref linkend="lo"/></member>
   <member><xref linkend="ltree"/></member>
   <member><xref