<varlistentry>
     <term><replaceable class="parameter">join_proc</replaceable></term>
     <listitem>
       <para>
         The join selectivity estimator function for this operator; write NONE to remove existing selectivity estimator.
       </para>
     </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">com_op</replaceable></term>
    <listitem>
     <para>
      The commutator of this operator. Can only be changed if the operator
      does not have an existing commutator.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">neg_op</replaceable></term>
    <listitem>
     <para>
      The negator of this operator. Can only be changed if the operator does
      not have an existing negator.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>HASHES</literal></term>
    <listitem>
     <para>
      Indicates this operator can support a hash join. Can only be enabled and
      not disabled.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>MERGES</literal></term>
    <listitem>
     <para>
      Indicates this operator can support a merge join. Can only be enabled
      and not disabled.
     </para>
    </listitem>
   </varlistentry>

  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   Refer to <xref linkend="xoper"/> and
   <xref linkend="xoper-optimization"/> for further information.
  </para>

  <para>
   Since commutators come in pairs that are commutators of each other,
   <literal>ALTER OPERATOR SET COMMUTATOR</literal> will also set the
   commutator of the <replaceable class="parameter">com_op</replaceable>
   to be the target operator.  Likewise, <literal>ALTER OPERATOR SET
   NEGATOR</literal> will also set the negator of
   the <replaceable class="parameter">neg_op</replaceable> to be the
   target operator.  Therefore, you must own the commutator or negator
   operator as well as the target operator.
  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   Change the owner of a custom operator <literal>a @@ b</literal> for type <type>text</type>:
<programlisting>
ALTER OPERATOR @@ (text, text) OWNER TO joe;
</programlisting>
  </para>

  <para>
   Change the restriction and join selectivity estimator functions of a
   custom operator <literal>a &amp;&amp; b</literal> for
   type <type>int[]</type>:
<programlisting>
ALTER OPERATOR &amp;&amp; (int[], int[]) SET (RESTRICT = _int_contsel, JOIN = _int_contjoinsel);
</programlisting>
  </para>

  <para>
   Mark the <literal>&amp;&amp;</literal> operator as being its own
   commutator:
<programlisting>
ALTER OPERATOR &amp;&amp; (int[], int[]) SET (COMMUTATOR = &amp;&amp;);
</programlisting>
  </para>

 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   There is no <command>ALTER OPERATOR</command> statement in
   the SQL standard.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-createoperator"/></member>
   <member><xref linkend="sql-dropoperator"/></member>
  </simplelist>
 </refsect1>
</refentry>