Internally, an LSN is a 64-bit integer, representing a byte position in
    the write-ahead log stream.  It is printed as two hexadecimal numbers of
    up to 8 digits each, separated by a slash; for example,
    <code class="literal">16/B374D848</code>.  The <code class="type">pg_lsn</code> type supports the
    standard comparison operators, like <code class="literal">=</code> and
    <code class="literal">&gt;</code>.  Two LSNs can be subtracted using the
    <code class="literal">-</code> operator; the 