able
      syntax in <code class="command">CREATE OPERATOR CLASS</code>, the operand data types
      must always be specified.
     </p><p>
      In an <code class="literal">ADD FUNCTION</code> clause, the operand data type(s) the
      function is intended to support, if different from
      the input data type(s) of the function.  For B-tree comparison functions
      and hash functions it is not necessary to specify <em class="replaceable"><code>op_type</code></em> since the function's input
      data 