Update xindex.sgml for recent additions to GIST opclass API.

Commit d04c8ed904 added another support function to the GIST API,
but overlooked mentioning it in xindex.sgml's summary of index support
functions.

Anastasia Lubennikova

doc/src/sgml/xindex.sgml

@@ -416,8 +416,8 @@
    </table>
 
   <para>
-   GiST indexes require seven support functions, with an optional eighth, as
-   shown in <xref linkend="xindex-gist-support-table">.
+   GiST indexes have nine support functions, two of which are optional,
+   as shown in <xref linkend="xindex-gist-support-table">.
    (For more information see <xref linkend="GiST">.)
   </para>
 
@@ -477,6 +477,12 @@
        <entry>determine distance from key to query value (optional)</entry>
        <entry>8</entry>
       </row>
+      <row>
+       <entry><function>fetch</></entry>
+       <entry>compute original representation of a compressed key for
+       index-only scans (optional)</entry>
+       <entry>9</entry>
+      </row>
      </tbody>
     </tgroup>
    </table>
@@ -530,8 +536,8 @@
    </table>
 
   <para>
-   GIN indexes require four support functions, with an optional fifth, as
-   shown in <xref linkend="xindex-gin-support-table">.
+   GIN indexes have six support functions, three of which are optional,
+   as shown in <xref linkend="xindex-gin-support-table">.
    (For more information see <xref linkend="GIN">.)
   </para>