code> entry.  Normally this will happen
   only for semantically equivalent queries, but there is a small chance of
   hash collisions causing unrelated queries to be merged into one entry.
   (This cannot happen for queries belonging to different users or databases,
   however.)
  </p><p>
   Since the <code class="structfield">queryid</code> hash value is computed on the
   post-parse-analysis representation of the queries, the opposite is
   also possible: queries with identical texts might appear as
   s