public RelOptCost minus(RelOptCost other) {
    if (this == INFINITY) {
      return this;
    }

    return new HiveCost(this.rowCount - other.getRows(), this.cpu - other.getCpu(),
        this.io - other.getIo());
  }
NOTE:<br>
1. HiveCost normalizes cpu and io in to time.<br>
2. CPU, IO cost is added together to find the query latency.<br>
3. If query latency is equal then row count is compared.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/cost/HiveCost.java