@Override
  public long calculateMaxReturnSize() {
    return maxReturnSize;
  }
This field indicates each data type for output columns(not including time column) of
TimeJoinOperator its size should be equal to outputColumnCount.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/join/FullOuterTimeJoinOperator.java