@Override
  public long calculateRetainedSizeAfterCallingNext() {
    return leftChild.calculateMaxReturnSize()
        + leftChild.calculateRetainedSizeAfterCallingNext()
        + rightChild.calculateMaxReturnSize()
        + rightChild.calculateRetainedSizeAfterCallingNext()
        + maxReturnSize;
  }
@return true if current right block is consumed up
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/source/relational/AbstractMergeSortJoinOperator.java