private Double computeConjunctionSelectivity(RexCall call) {
    Double tmpSelectivity;
    double selectivity = 1;

    for (RexNode cje : call.getOperands()) {
      tmpSelectivity = cje.accept(this);
      if (tmpSelectivity != null) {
        selectivity *= tmpSelectivity;
      }
    }

    return selectivity;
  }
Selectivity of conjunctive predicate -> (selectivity of conjunctive
element1) * (selectivity of conjunctive element2)...

@param call
@return
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/stats/FilterSelectivityEstimator.java