presto-parquet/src/main/java/io/prestosql/parquet/reader/ParquetReader.java/ParquetReader/advanceToNextRowGroup
class ParquetReader:    private boolean advanceToNextRowGroup()
    {
        currentRowGroupMemoryContext.close();
        currentRowGroupMemoryContext = systemMemoryContext.newAggregatedMemoryContext();

        freeCurrentRowGroupBuffers();
        currentRowGroup++;
        if (currentRowGroup == blocks.size()) {
            return false;
        }
        currentBlockMetadata = blocks.get(currentRowGroup);

        nextRowInGroup = 0L;
        currentGroupRowCount = currentBlockMetadata.getRowCount();
        initializeColumnReaders();
        return true;
    }