<structfield>relfilenode</structfield> parameters reference
      <link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.<structfield>oid</structfield>,
      <link linkend="catalog-pg-database"><structname>pg_database</structname></link>.<structfield>oid</structfield>, and
      <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relfilenode</structfield>
      respectively.  The <structfield>relforknumber</structfield>
      field is the fork number within the relation for the block
      reference; see <filename>common/relpath.h</filename> for
      details.
     </para>
     <tip>
      <para>
       The <function>pg_filenode_relation</function> function (see
       <xref linkend="functions-admin-dblocation"/>) can help you to
       determine which relation was modified during original execution.
      </para>
     </tip>
     <para>
      It is possible for clients to avoid the overhead of
      materializing block data.  This may make function execution
      significantly faster.  When <replaceable>show_data</replaceable>
      is set to <literal>false</literal>, <structfield>block_data</structfield>
      and <structfield>block_fpi_data</structfield> values are omitted
      (that is, the <structfield>block_data</structfield> and
      <structfield>block_fpi_data</structfield> <literal>OUT</literal>
      arguments are <literal>NULL</literal> for all rows returned).
      Obviously, this optimization is only feasible with queries where
      block data isn't truly required.
     </para>
     <para>
      The function raises an error if
      <replaceable>start_lsn</replaceable> is not available.
     </para>
    </listitem>
   </varlistentry>

    <varlistentry id="pgwalinspect-funcs-pg-get-wal-stats">
    <term>
     <function>
      pg_get_wal_stats(start_lsn pg_lsn, end_lsn pg_lsn, per_record boolean DEFAULT false)
      returns setof record
     </function>
    </term>

    <listitem>
     <para>
      Gets statistics of all the valid WAL records between
      <replaceable>start_lsn</replaceable> and
      <replaceable>end_lsn</replaceable>. By default, it returns one row per
      <replaceable>resource_manager</replaceable> type. When
      <replaceable>per_record</replaceable> is set to <literal>true</literal>,
      it returns one row per <replaceable>record_type</replaceable>.
      For example:
<screen>
postgres=# SELECT * FROM pg_get_wal_stats('0/1E847D00', '0/1E84F500')
           WHERE count > 0 AND
                 "resource_manager/record_type" = 'Transaction'
           LIMIT 1;
-[ RECORD 1 ]----------------+-------------------
resource_manager/record_type | Transaction
count                        | 2
count_percentage             | 8
record_size                  | 875
record_size_percentage       | 41.23468426013195
fpi_size                     | 0
fpi_size_percentage          | 0
combined_size                | 875
combined_size_percentage     | 2.8634072910530795
</screen>
     </para>
     <para>
      The function raises an error if
      <replaceable>start_lsn</replaceable> is not available.
     </para>
    </listitem>
   </varlistentry>

  </variablelist>
 </sect2>

 <sect2 id="pgwalinspect-author">
  <title>Author</title>

  <para>
   Bharath Rupireddy <email>bharath.rupireddyforpostgres@gmail.com</email>
  </para>
 </sect2>

</sect1>