the underlying B-Tree index
      access method code.  Note that
      <function>bt_index_parent_check</function> cannot be used when
      hot standby mode is enabled (i.e., on read-only physical
      replicas), unlike <function>bt_index_check</function>.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term>
     <function>gin_index_check(index regclass) returns void</function>
     <indexterm>
      <primary>gin_index_check</primary>
     </indexterm>
    </term>

    <listitem>
     <para>
      <function>gin_index_check</function> tests that its target GIN index
      has consistent parent-child tuples relations (no parent tuples
      require tuple adjustment) and page graph respects balanced-tree
      invariants (internal pages reference only leaf page or only internal
      pages).
     </para>
    </listitem>
   </varlistentry>

  </variablelist>
  <tip>
   <para>
    <function>bt_index_check</function> and
    <function>bt_index_parent_check</function> both output log
    messages about the verification process at
    <literal>DEBUG1</literal> and <literal>DEBUG2</literal> severity
    levels.  These messages provide detailed information about the
    verification process that may be of interest to
    <productname>PostgreSQL</productname> developers.  Advanced users
    may also find this information helpful, since it provides
    additional context should verification actually detect an
    inconsistency.  Running:
<programlisting>
SET client_min_messages = DEBUG1;
</programlisting>
    in an interactive <application>psql</application> session before
    running a verification query will display messages about the
    progress of verification with a manageable level of detail.
   </para>
  </tip>

  <variablelist>
   <varlistentry>
    <term>
     <function>
      verify_heapam(relation regclass,
                    on_error_stop boolean,
                    check_toast boolean,
                    skip text,
                    startblock bigint,
                    endblock bigint,
                    blkno OUT bigint,
                    offnum OUT integer,
                    attnum OUT integer,
                    msg OUT text)
      returns setof record
     </function>
    </term>
    <listitem>
     <para>
      Checks a table, sequence, or materialized view for structural corruption,
      where pages in the relation contain data that is invalidly formatted, and
      for logical corruption, where pages are structurally valid but
      inconsistent with the rest of the database cluster.
     </para>
     <para>
      The following optional arguments are recognized:
     </para>
     <variablelist>
      <varlistentry>
       <term><literal>on_error_stop</literal></term>
       <listitem>
        <para>
         If true, corruption checking stops at the end of the first block in
         which any corruptions are found.
        </para>
        <para>
         Defaults to false.
        </para>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term><literal>check_toast</literal></term>
       <listitem>
        <para>
         If true, toasted values are checked against the target relation's
         TOAST table.
        </para>
        <para>
         This option is known to be slow.  Also, if the toast table or its
         index is corrupt, checking it against toast values could conceivably
         crash the server, although in many cases this would just produce an
         error.
        </para>
        <para>
         Defaults to false.
        </para>
       </listitem>
      </varlistentry>
      <varlistentry>
       <term><literal>skip</literal></term>
       <listitem>
        <para>
         If not <literal>none</literal>, corruption checking skips blocks that
         are marked as all-visible or all-frozen, as specified.
         Valid options are <literal>all-visible</literal>,
         <literal>all-frozen</literal> and <literal>none</literal>.