@RequiresNonNull({"joinStart", "nFieldsInJoinFactor"})
  ImmutableBitSet getJoinFilterFactorBitmap(
          @UnderInitialization HiveLoptMultiJoin this,
          RexNode joinFilter,
          boolean setFields) {
    ImmutableBitSet fieldRefBitmap = fieldBitmap(joinFilter);
    if (setFields) {
      fieldsRefByJoinFilter.put(joinFilter, fieldRefBitmap);
    }

    return factorBitmap(fieldRefBitmap);
  }
Returns a bitmap representing the factors referenced in a join filter.

@param joinFilter the join filter
@param setFields if true, add the fields referenced by the join filter
into a map

@return the bitmap containing the factor references
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveLoptMultiJoin.java