@Override
  protected TsBlock getNextTsBlock(int childIndex) throws Exception {
    inputIndex[childIndex] = 0;
    return children.get(childIndex).nextWithTimer();
  }
@param currentChildIndex the index of the child
@throws Exception Potential Exception thrown by Operator.close()
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/join/FullOuterTimeJoinOperator.java