fields of the
   referenced <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link> entry.
  </para>

 </sect1>


 <sect1 id="catalog-pg-amproc">
  <title><structname>pg_amproc</structname></title>

  <indexterm zone="catalog-pg-amproc">
   <primary>pg_amproc</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_amproc</structname> stores information about
   support functions associated with access method operator families.  There
   is one row for each support function belonging to an operator family.
  </para>

  <table>
   <title><structname>pg_amproc</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocfamily</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The operator family this entry is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amproclefttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Left-hand input data type of associated operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocrighttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Right-hand input data type of associated operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocnum</structfield> <type>int2</type>
      </para>
      <para>
       Support function number
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amproc</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the function
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The usual interpretation of the
   <structfield>amproclefttype</structfield> and <structfield>amprocrighttype</structfield> fields
   is that they identify the left and right input types of the operator(s)
   that a particular support function supports.  For some access methods
   these match the input data type(s) of the support function itself, for
   others not.  There is a notion of <quote>default</quote> support functions for
   an index, which are those with <structfield>amproclefttype</structfield> and
   <structfield>amprocrighttype</structfield> both equal to the index operator class's
   <structfield>opcintype</structfield>.
  </para>

 </sect1>


 <sect1 id="catalog-pg-attrdef">
  <title><structname>pg_attrdef</structname></title>

  <indexterm zone="catalog-pg-attrdef">
   <primary>pg_attrdef</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_attrdef</structname> stores column default
   expressions and generation expressions.  The main information about columns
   is stored in <link
   linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.