public void fetchChunkInfo()

in tsfile-viewer-core/src/main/java/org/apache/iotdb/tool/core/service/TsFileAnalyserV13.java [382:520]
108 lines of code
19 McCabe index (conditional complexity)

  public void fetchChunkInfo(ChunkGroupMetaInfo chunkGroupMetaInfo) throws IOException {
    long chunkOffset = reader.position() - 1;
    // ChunkHeader 中的 marker：判断 chunk 的开始，对齐或非对齐
    ChunkHeader chunkHeader = reader.readChunkHeader(chunkGroupMetaInfo.getMarker());

    // 0 NonAligned, 1 TimeColumn, 2 ValueColumn
    int alignedFlag = 0;

    String measurementID = chunkHeader.getMeasurementID();
    IMeasurementSchema measurementSchema =
        new MeasurementSchema(
            measurementID,
            chunkHeader.getDataType(),
            chunkHeader.getEncodingType(),
            chunkHeader.getCompressionType());
    measurementSchemaList.add(measurementSchema);

    // TODO 不需要吧
    // 判断对其 or 非对齐
    TSDataType dataType = chunkHeader.getDataType();
    if (chunkHeader.getDataType() == TSDataType.VECTOR) {
      chunkGroupMetaInfo.getTimeBatch().clear();
    }

    // 跳过此 chunk 下所有的 page
    Statistics<? extends Serializable> chunkStatistics = Statistics.getStatsByType(dataType);
    int chunkDataSize = chunkHeader.getDataSize();
    if (chunkDataSize > 0) {
      // 此 chunk 中的 page 数量超过一页，需要通过每个 pageHeader 中的 statistic 构建并更新 chunk 的 statistic
      if (((byte) (chunkHeader.getChunkType() & CHUNK_HEADER_MASK)) == MetaMarker.CHUNK_HEADER) {
        // 1. 若是对齐时间序列
        // 1.1 TimeChunk（Pages）
        if ((chunkHeader.getChunkType() & TsFileConstant.TIME_COLUMN_MASK)
            == TsFileConstant.TIME_COLUMN_MASK) {
          alignedFlag = 1;
        } else if ((chunkHeader.getChunkType() & TsFileConstant.VALUE_COLUMN_MASK)
            == TsFileConstant.VALUE_COLUMN_MASK) {
          // 1.2 ValueChunk（Pages）
          alignedFlag = 2;
        }

        // 2. 读取 Chunk 中所有的 page
        while (chunkDataSize > 0) {
          // a new Page
          PageHeader pageHeader = reader.readPageHeader(chunkHeader.getDataType(), true);
          if (pageHeader.getUncompressedSize() != 0) {
            // not empty page
            chunkStatistics.mergeStatistics(pageHeader.getStatistics());
          }
          // 跳过 Page 中具体的数据
          reader.skipPageData(pageHeader);
          // 减去 pageHeader 的长度
          chunkDataSize -= pageHeader.getSerializedPageSize();
          chunkHeader.increasePageNums(1);
        }
      } else {
        // only one page without statistic, we need to iterate each point to generate chunk
        // statistic
        PageHeader pageHeader = reader.readPageHeader(chunkHeader.getDataType(), false);
        System.out.println(
            "only one page without statistic, reader position1:" + reader.position());
        Decoder valueDecoder =
            Decoder.getDecoderByType(chunkHeader.getEncodingType(), chunkHeader.getDataType());
        ByteBuffer pageData = reader.readPage(pageHeader, chunkHeader.getCompressionType());
        System.out.println(
            "only one page without statistic, reader position2:" + reader.position());
        Decoder timeDecoder =
            Decoder.getDecoderByType(
                TSEncoding.valueOf(TSFileDescriptor.getInstance().getConfig().getTimeEncoder()),
                TSDataType.INT64);

        if ((chunkHeader.getChunkType() & TsFileConstant.TIME_COLUMN_MASK)
            == TsFileConstant.TIME_COLUMN_MASK) {
          // Time Chunk with only one page
          TimePageReader timePageReader = new TimePageReader(pageHeader, pageData, timeDecoder);
          long[] currentTimeBatch = timePageReader.getNextTimeBatch();
          chunkGroupMetaInfo.getTimeBatch().add(currentTimeBatch);
          // 遍历每个时间点，并更新 chunk 的 statistic
          for (long currentTime : currentTimeBatch) {
            chunkStatistics.update(currentTime);
          }
          alignedFlag = 1;
        } else if ((chunkHeader.getChunkType() & TsFileConstant.VALUE_COLUMN_MASK)
            == TsFileConstant.VALUE_COLUMN_MASK) {
          // Value Chunk with only one page
          ValuePageReader valuePageReader =
              new ValuePageReader(pageHeader, pageData, chunkHeader.getDataType(), valueDecoder);
          TsPrimitiveType[] valueBatch =
              valuePageReader.nextValueBatch(chunkGroupMetaInfo.getTimeBatch().get(0));
          // 遍历每个数据点，并更新 chunk 的 statistic
          if (valueBatch != null && valueBatch.length != 0) {
            for (int i = 0; i < valueBatch.length; i++) {
              TsPrimitiveType value = valueBatch[i];
              if (value == null) {
                continue;
              }
              long timeStamp = chunkGroupMetaInfo.getTimeBatch().get(0)[i];
              setChunkStatistics(chunkStatistics, timeStamp, value, dataType);
            }
          }
          alignedFlag = 2;
        } else {
          // NonAligned Chunk with only one page
          PageReader pageReader =
              new PageReader(
                  pageHeader, pageData, chunkHeader.getDataType(), valueDecoder, timeDecoder, null);
          BatchData batchData = pageReader.getAllSatisfiedPageData();
          while (batchData.hasCurrent()) {
            setChunkStatistics(
                chunkStatistics,
                batchData.currentTime(),
                batchData.currentTsPrimitiveType(),
                dataType);
            batchData.next();
          }
          alignedFlag = 0;
        }
        chunkHeader.increasePageNums(1);
      }
    }

    // 构建 chunkMetadata
    ChunkMetadata chunkMetadata =
        new ChunkMetadata(measurementID, dataType, chunkOffset, chunkStatistics);

    if (alignedFlag == 1) {
      chunkGroupMetaInfo.setAlignedTimeChunkMetadata(chunkMetadata);
      chunkGroupMetaInfo.getChunkHeaderList().add(chunkHeader);
    } else if (alignedFlag == 2) {
      chunkGroupMetaInfo.getAlignedValueChunkMetadata().add(chunkMetadata);
      chunkGroupMetaInfo.getChunkHeaderList().add(chunkHeader);
    } else if (alignedFlag == 3) {

      chunkGroupMetaInfo.getChunkHeaderList().add(chunkHeader);
    } else {
      chunkGroupMetaInfo.getChunkMetadataList().add(chunkMetadata);
      chunkGroupMetaInfo.getChunkHeaderList().add(chunkHeader);
    }
  }