form a self-consistent set.  It is the user's
   responsibility to define a valid operator class.
  </para>

  <para>
   Related operator classes can be grouped into <firstterm>operator
   families</firstterm>.  To add a new operator class to an existing family,
   specify the <literal>FAMILY</literal> option in <command>CREATE OPERATOR
   CLASS</command>.  Without this option, the new class is placed into
   a family named the same as the new class (creating that family if
   it doesn't already exist).
  </para>

  <para>
   Refer to <xref linkend="xindex"/> for further information.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name of the operator class to be created.  The name can be
      schema-qualified.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>DEFAULT</literal></term>
    <listitem>
     <para>
      If present, the operator class will become the default
      operator class for its data type.  At most one operator class
      can be the default for a specific data type and index method.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">data_type</replaceable></term>
    <listitem>
     <para>
      The column data type that this operator class is for.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">index_method</replaceable></term>
    <listitem>
     <para>
      The name of the index method this operator class is for.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">family_name</replaceable></term>
    <listitem>
     <para>
      The name of the existing operator family to add this operator class to.
      If not specified, a family named the same as the operator class is
      used (creating it, if it doesn't already exist).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">strategy_number</replaceable></term>
    <listitem>
     <para>
      The index method's strategy number for an operator
      associated with the operator class.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">operator_name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an operator associated
      with the operator class.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">op_type</replaceable></term>
    <listitem>
     <para>
      In an <literal>OPERATOR</literal> clause,
      the operand data type(s) of the operator, or <literal>NONE</literal> to
      signify a prefix operator.  The operand data
      types can be omitted in the normal case where they are the same
      as the operator class's data type.
     </para>

     <para>
      In a <literal>FUNCTION</literal> 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)
      or the class's data type (for B-tree sort support functions,
      B-tree equal image functions, and all functions in GiST,
      SP-GiST, GIN and BRIN operator classes).  These defaults are
      correct, and so <replaceable
       class="parameter">op_type</replaceable> need not be specified
      in <literal>FUNCTION</literal> clauses, except for the case of a
      B-tree sort support function that is meant to support
      cross-data-type comparisons.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">sort_family_name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing