Example of creating such an index with the default signature length of 8 bytes:
    </para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (path);
</programlisting>
    <para>
     Example of creating such an index with a signature length of 100 bytes:
    </para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (path gist_ltree_ops(siglen=100));
</programlisting>
   </listitem>
   <listitem>
    <para>
     GiST index over <type>ltree[]</type> (<literal>gist__ltree_ops</literal>
     opclass):
     <literal>ltree[] &lt;@ ltree</literal>, <literal>ltree @&gt; ltree[]</literal>,
     <literal>@</literal>, <literal>~</literal>, <literal>?</literal>
    </para>
    <para>
     <literal>gist__ltree_ops</literal> GiST opclass works similarly to
     <literal>gist_ltree_ops</literal> and also takes signature length as
     a parameter.  The default value of <literal>siglen</literal> in
      <literal>gist__ltree_ops</literal> is 28 bytes.
    </para>
    <para>
     Example of creating such an index with the default signature length of 28 bytes:
    </para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (array_path);
</programlisting>
    <para>
     Example of creating such an index with a signature length of 100 bytes:
    </para>
<programlisting>
CREATE INDEX path_gist_idx ON test USING GIST (array_path gist__ltree_ops(siglen=100));
</programlisting>
    <para>
     Note: This index type is lossy.
    </para>
   </listitem>
  </itemizedlist>
 </sect2>

 <sect2 id="ltree-example">
  <title>Example</title>

  <para>
   This example uses the following data (also available in file
   <filename>contrib/ltree/ltreetest.sql</filename> in the source distribution):
  </para>

<programlisting>
CREATE TABLE test (path ltree);
INSERT INTO test VALUES ('Top');
INSERT INTO test VALUES ('Top.Science');
INSERT INTO test VALUES ('Top.Science.Astronomy');
INSERT INTO test VALUES ('Top.Science.Astronomy.Astrophysics');
INSERT INTO test VALUES ('Top.Science.Astronomy.Cosmology');
INSERT INTO test VALUES ('Top.Hobbies');
INSERT INTO test VALUES ('Top.Hobbies.Amateurs_Astronomy');
INSERT INTO test VALUES ('Top.Collections');
INSERT INTO test VALUES ('Top.Collections.Pictures');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Stars');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Galaxies');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Astronauts');
CREATE INDEX path_gist_idx ON test USING GIST (path);
CREATE INDEX path_idx ON test USING BTREE (path);
CREATE INDEX path_hash_idx ON test USING HASH (path);
</programlisting>

  <para>
   Now, we have a table <structname>test</structname> populated with data describing
   the hierarchy shown below:
  </para>

<literallayout class="monospaced">
                        Top
                     /   |  \
             Science Hobbies Collections
                 /       |              \
        Astronomy   Amateurs_Astronomy Pictures
           /  \                            |
Astrophysics  Cosmology                Astronomy
                                        /  |    \
                                 Galaxies Stars Astronauts
</literallayout>

  <para>
   We can do inheritance:
<screen>
ltreetest=&gt; SELECT path FROM