public DataPage readPage()

in exec/java-exec/src/main/java/org/apache/parquet/hadoop/ColumnChunkIncReadStore.java [147:275]
115 lines of code
9 McCabe index (conditional complexity)

    public DataPage readPage() {
      PageHeader pageHeader = new PageHeader();
      try {
        if (lastPage != null) {
          lastPage.release();
          lastPage = null;
        }
        while(valueReadSoFar < metaData.getValueCount()) {
          pageHeader = Util.readPageHeader(in);
          int compPageSize = pageHeader.getCompressed_page_size();
          int pageSize = pageHeader.getUncompressed_page_size();
          DataPageHeaderInfoProvider pageHeaderInfo;

          switch (pageHeader.type) {
            case DICTIONARY_PAGE:
              if (dictionaryPage == null) {
                BytesInput pageBytes = decompressor.decompress(
                    BytesInput.from(in, compPageSize),
                    pageSize
                );

                dictionaryPage = new DictionaryPage(
                    pageBytes,
                    pageSize,
                    METADATA_CONVERTER.getEncoding(pageHeader.dictionary_page_header.encoding)
                );
              } else {
                in.skip(compPageSize);
              }
              break;
            case DATA_PAGE:
              pageHeaderInfo = DataPageHeaderInfoProvider.builder(pageHeader);
              valueReadSoFar += pageHeaderInfo.getNumValues();
              ByteBuf buf = allocator.buffer(compPageSize);
              lastPage = buf;
              ByteBuffer pageBuf = buf.nioBuffer(0, compPageSize);
              HadoopStreams.wrap(in).readFully(pageBuf);
              pageBuf.flip();

              BytesInput pageBytes = decompressor.decompress(BytesInput.from(pageBuf), pageSize);

              Statistics stats = METADATA_CONVERTER.fromParquetStatistics(
                null,
                pageHeaderInfo.getStatistics(),
                columnDescriptor.getPrimitiveType()
              );

              return new DataPageV1(
                  pageBytes,
                  pageHeaderInfo.getNumValues(),
                  pageSize,
                  stats,
                  METADATA_CONVERTER.getEncoding(pageHeaderInfo.getRepetitionLevelEncoding()),
                  METADATA_CONVERTER.getEncoding(pageHeaderInfo.getDefinitionLevelEncoding()),
                  METADATA_CONVERTER.getEncoding(pageHeaderInfo.getEncoding())
              );
            case DATA_PAGE_V2:
              pageHeaderInfo = DataPageHeaderInfoProvider.builder(pageHeader);
              int repLevelSize = pageHeader.data_page_header_v2.getRepetition_levels_byte_length();
              int defLevelSize = pageHeader.data_page_header_v2.getDefinition_levels_byte_length();
              valueReadSoFar += pageHeaderInfo.getNumValues();

              buf = allocator.buffer(compPageSize);
              lastPage = buf;
              pageBuf = buf.nioBuffer(0, compPageSize);
              HadoopStreams.wrap(in).readFully(pageBuf);
              pageBuf.flip();

              // Note that the repetition and definition levels are stored uncompressed in
              // the v2 page format.
              int pageBufOffset = 0;
              ByteBuffer bb = (ByteBuffer) pageBuf.position(pageBufOffset);
              BytesInput repLevelBytes = BytesInput.from(
                (ByteBuffer) bb.slice().limit(repLevelSize)
              );
              pageBufOffset += repLevelSize;

              bb = (ByteBuffer) pageBuf.position(pageBufOffset);
              final BytesInput defLevelBytes = BytesInput.from(
                (ByteBuffer) bb.slice().limit(defLevelSize)
              );
              pageBufOffset += defLevelSize;

              // we've now reached the beginning of compressed column data
              bb = (ByteBuffer) pageBuf.position(pageBufOffset);
              final BytesInput colDataBytes = decompressor.decompress(
                BytesInput.from((ByteBuffer) bb.slice()),
                pageSize - repLevelSize - defLevelSize
              );

              stats = METADATA_CONVERTER.fromParquetStatistics(
                null,
                pageHeaderInfo.getStatistics(),
                columnDescriptor.getPrimitiveType()
              );

              return new DataPageV2(
                pageHeader.data_page_header_v2.getNum_rows(),
                pageHeader.data_page_header_v2.getNum_nulls(),
                pageHeaderInfo.getNumValues(),
                repLevelBytes,
                defLevelBytes,
                METADATA_CONVERTER.getEncoding(pageHeaderInfo.getEncoding()),
                colDataBytes,
                pageSize,
                stats,
                pageHeader.data_page_header_v2.isIs_compressed()
              );
            default:
              logger.warn("skipping page of type {} of size {}", pageHeader.getType(), compPageSize);
              in.skip(compPageSize);
              break;
          }
        }
        in.close();
        return null;
      } catch (OutOfMemoryException e) {
        throw e; // throw as it is
      } catch (Exception e) {
        throw new DrillRuntimeException("Error reading page." +
          "\nFile path: " + path.toUri().getPath() +
          "\nRow count: " + rowCount +
          "\nColumn Chunk Metadata: " + metaData +
          "\nPage Header: " + pageHeader +
          "\nFile offset: " + fileOffset +
          "\nSize: " + size +
          "\nValue read so far: " + valueReadSoFar, e);
      }
    }