parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java
public PageReadStore readNextRowGroup() throws IOException {
    if (currentBlock == blocks.size()) {
      return null;
    }
    BlockMetaData block = blocks.get(currentBlock);
    if (block.getRowCount() == 0) {
      throw new RuntimeException("Illegal row group of 0 rows");
    }
    this.currentRowGroup = new ColumnChunkPageReadStore(block.getRowCount());
    // prepare the list of consecutive parts to read them in one scan
    List<ConsecutivePartList> allParts = new ArrayList<ConsecutivePartList>();
    ConsecutivePartList currentParts = null;
    for (ColumnChunkMetaData mc : block.getColumns()) {
      ColumnPath pathKey = mc.getPath();
      BenchmarkCounter.incrementTotalBytes(mc.getTotalSize());
      ColumnDescriptor columnDescriptor = paths.get(pathKey);
      if (columnDescriptor != null) {
        long startingPos = mc.getStartingPos();
        // first part or not consecutive => new list
        if (currentParts == null || currentParts.endPos() != startingPos) {
          currentParts = new ConsecutivePartList(startingPos);
          allParts.add(currentParts);
        }
        currentParts.addChunk(new ChunkDescriptor(columnDescriptor, mc, startingPos, (int)mc.getTotalSize()));
      }
    }
    // actually read all the chunks
    ChunkListBuilder builder = new ChunkListBuilder();
    for (ConsecutivePartList consecutiveChunks : allParts) {
      consecutiveChunks.readAll(f, builder);
    }
    for (Chunk chunk : builder.build()) {
      currentRowGroup.addColumn(chunk.descriptor.col, chunk.readAllPages());
    }

    // avoid re-reading bytes the dictionary reader is used after this call
    if (nextDictionaryReader != null) {
      nextDictionaryReader.setRowGroup(currentRowGroup);
    }

    advanceToNextBlock();

    return currentRowGroup;
  }
public PageReadStore readNextRowGroup() throws IOException {
    if (currentBlock == blocks.size()) {
      return null;
    }
    BlockMetaData block = blocks.get(currentBlock);
    if (block.getRowCount() == 0) {
      throw new RuntimeException("Illegal row group of 0 rows");
    }
    this.currentRowGroup = new ColumnChunkPageReadStore(block.getRowCount());
    // prepare the list of consecutive parts to read them in one scan
    List<ConsecutivePartList> allParts = new ArrayList<ConsecutivePartList>();
    ConsecutivePartList currentParts = null;
    for (ColumnChunkMetaData mc : block.getColumns()) {
      ColumnPath pathKey = mc.getPath();
      BenchmarkCounter.incrementTotalBytes(mc.getTotalSize());
      ColumnDescriptor columnDescriptor = paths.get(pathKey);
      if (columnDescriptor != null) {
        long startingPos = mc.getStartingPos();
        // first part or not consecutive => new list
        if (currentParts == null || currentParts.endPos() != startingPos) {
          currentParts = new ConsecutivePartList(startingPos);
          allParts.add(currentParts);
        }
        currentParts.addChunk(new ChunkDescriptor(columnDescriptor, mc, startingPos, (int)mc.getTotalSize()));
      }
    }
    // actually read all the chunks
    ChunkListBuilder builder = new ChunkListBuilder();
    for (ConsecutivePartList consecutiveChunks : allParts) {
      consecutiveChunks.readAll(f, builder);
    }
    for (Chunk chunk : builder.build()) {
      currentRowGroup.addColumn(chunk.descriptor.col, chunk.readAllPages());
    }

    // avoid re-reading bytes the dictionary reader is used after this call
    if (nextDictionaryReader != null) {
      nextDictionaryReader.setRowGroup(currentRowGroup);
    }

    advanceToNextBlock();

    return currentRowGroup;
  }
Reads all the columns requested from the row group at the current file position.
@throws IOException if an error occurs while reading
@return the PageReadStore which can provide PageReaders for each column.