public PageReadStore readNextFilteredRowGroup() throws IOException {
    if (currentBlock == blocks.size()) {
      return null;
    }
    if (!options.useColumnIndexFilter()) {
      return readNextRowGroup();
    }
    BlockMetaData block = blocks.get(currentBlock);
    if (block.getRowCount() == 0) {
      throw new RuntimeException("Illegal row group of 0 rows");
    }
    ColumnIndexStore ciStore = getColumnIndexStore(currentBlock);
    RowRanges rowRanges = getRowRanges(currentBlock);
    long rowCount = rowRanges.rowCount();
    if (rowCount == 0) {
      // There are no matching rows -> skipping this row-group
      advanceToNextBlock();
      return readNextFilteredRowGroup();
    }
    if (rowCount == block.getRowCount()) {
      // All rows are matching -> fall back to the non-filtering path
      return readNextRowGroup();
    }

    this.currentRowGroup = new ColumnChunkPageReadStore(rowRanges);
    // prepare the list of consecutive parts to read them in one scan
    ChunkListBuilder builder = new ChunkListBuilder();
    List<ConsecutivePartList> allParts = new ArrayList<ConsecutivePartList>();
    ConsecutivePartList currentParts = null;
    for (ColumnChunkMetaData mc : block.getColumns()) {
      ColumnPath pathKey = mc.getPath();
      ColumnDescriptor columnDescriptor = paths.get(pathKey);
      if (columnDescriptor != null) {
        OffsetIndex offsetIndex = ciStore.getOffsetIndex(mc.getPath());

        OffsetIndex filteredOffsetIndex = filterOffsetIndex(offsetIndex, rowRanges,
            block.getRowCount());
        for (OffsetRange range : calculateOffsetRanges(filteredOffsetIndex, mc, offsetIndex.getOffset(0))) {
          BenchmarkCounter.incrementTotalBytes(range.getLength());
          long startingPos = range.getOffset();
          // first part or not consecutive => new list
          if (currentParts == null || currentParts.endPos() != startingPos) {
            currentParts = new ConsecutivePartList(startingPos);
            allParts.add(currentParts);
          }
          ChunkDescriptor chunkDescriptor = new ChunkDescriptor(columnDescriptor, mc, startingPos,
              (int) range.getLength());
          currentParts.addChunk(chunkDescriptor);
          builder.setOffsetIndex(chunkDescriptor, filteredOffsetIndex);
        }
      }
    }
    // actually read all the chunks
    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 readNextFilteredRowGroup ( ) throws IOException { if ( currentBlock == blocks . size ( ) ) { return null ; } if ( ! options . useColumnIndexFilter ( ) ) { return readNextRowGroup ( ) ; } BlockMetaData block = blocks . get ( currentBlock ) ; if ( block . getRowCount ( ) == 0 ) { throw new RuntimeException ( "Illegal row group of 0 rows" ) ; } ColumnIndexStore ciStore = getColumnIndexStore ( currentBlock ) ; RowRanges rowRanges = getRowRanges ( currentBlock ) ; long rowCount = rowRanges . rowCount ( ) ; if ( rowCount == 0 ) { advanceToNextBlock ( ) ; return readNextFilteredRowGroup ( ) ; } if ( rowCount == block . getRowCount ( ) ) { return readNextRowGroup ( ) ; } this . currentRowGroup = new ColumnChunkPageReadStore ( rowRanges ) ; ChunkListBuilder builder = new ChunkListBuilder ( ) ; List < ConsecutivePartList > allParts = new ArrayList < ConsecutivePartList > ( ) ; ConsecutivePartList currentParts = null ; for ( ColumnChunkMetaData mc : block . getColumns ( ) ) { ColumnPath pathKey = mc . getPath ( ) ; ColumnDescriptor columnDescriptor = paths . get ( pathKey ) ; if ( columnDescriptor != null ) { OffsetIndex offsetIndex = ciStore . getOffsetIndex ( mc . getPath ( ) ) ; OffsetIndex filteredOffsetIndex = filterOffsetIndex ( offsetIndex , rowRanges , block . getRowCount ( ) ) ; for ( OffsetRange range : calculateOffsetRanges ( filteredOffsetIndex , mc , offsetIndex . getOffset ( 0 ) ) ) { BenchmarkCounter . incrementTotalBytes ( range . getLength ( ) ) ; long startingPos = range . getOffset ( ) ; if ( currentParts == null || currentParts . endPos ( ) != startingPos ) { currentParts = new ConsecutivePartList ( startingPos ) ; allParts . add ( currentParts ) ; } ChunkDescriptor chunkDescriptor = new ChunkDescriptor ( columnDescriptor , mc , startingPos , ( int ) range . getLength ( ) ) ; currentParts . addChunk ( chunkDescriptor ) ; builder . setOffsetIndex ( chunkDescriptor , filteredOffsetIndex ) ; } } } for ( ConsecutivePartList consecutiveChunks : allParts ) { consecutiveChunks . readAll ( f , builder ) ; } for ( Chunk chunk : builder . build ( ) ) { currentRowGroup . addColumn ( chunk . descriptor . col , chunk . readAllPages ( ) ) ; } if ( nextDictionaryReader != null ) { nextDictionaryReader . setRowGroup ( currentRowGroup ) ; } advanceToNextBlock ( ) ; return currentRowGroup ; }
Reads all the columns requested from the row group at the current file position. It may skip specific pages based
on the column indexes according to the actual filter. As the rows are not aligned among the pages of the different
columns row synchronization might be required. See the documentation of the class SynchronizingColumnReader for
details.

@return the PageReadStore which can provide PageReaders for each column
@throws IOException
if any I/O error occurs while reading