public Double getPercentageOriginalRows(AggregateRelBase rel) {
    // REVIEW jvs 28-Mar-2006: The assumption here seems to be that
    // aggregation does not apply any filtering, so it does not modify the
    // percentage.  That's very much oversimplified.

    return RelMetadataQuery.getPercentageOriginalRows(rel.getChild());
  }