presto-parquet/src/main/java/io/prestosql/parquet/reader/ParquetReader.java/ParquetReader/nextBatch
class ParquetReader:    public int nextBatch()
    {
        if (nextRowInGroup >= currentGroupRowCount && !advanceToNextRowGroup()) {
            return -1;
        }

        batchSize = toIntExact(min(nextBatchSize, maxBatchSize));
        nextBatchSize = min(batchSize * BATCH_SIZE_GROWTH_FACTOR, MAX_VECTOR_LENGTH);
        batchSize = toIntExact(min(batchSize, currentGroupRowCount - nextRowInGroup));

        nextRowInGroup += batchSize;
        Arrays.stream(columnReaders)
                .forEach(reader -> reader.prepareNextRead(batchSize));
        return batchSize;
    }