@Override
  public boolean needPrepareForNext(
      long rowIndex, Column valueColumn, int lastRowIndexForNonNullHelperColumn) {
    return nextRowIndex < rowIndex
        && lastRowIndexForNonNullHelperColumn >= 0
        && valueColumn.isNull(lastRowIndexForNonNullHelperColumn);
  }
Whether need prepare for next.

@param rowIndex end time of current valueColumn that need to be filled
@param valueColumn valueColumn that need to be filled
@return true if valueColumn can't be filled using current information, and we need to get next
    TsBlock and then call prepareForNext. false if valueColumn can be filled using current
    information, and we can directly call fill() function
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/fill/linear/LinearFill.java