presto-orc/src/main/java/io/prestosql/orc/AbstractOrcDataSource.java/MergedOrcDataReader/seekBuffer
class MergedOrcDataReader:        @Override
        public Slice seekBuffer(int newPosition)
                throws IOException
        {
            if (data == null) {
                data = lazyBufferLoader.loadNestedDiskRangeBuffer(diskRange);
                if (data == null) {
                    throw new OrcCorruptionException(id, "Data loader returned null");
                }
                if (data.length() != diskRange.getLength()) {
                    throw new OrcCorruptionException(id, "Expected to load %s bytes, but %s bytes were loaded", diskRange.getLength(), data.length());
                }
            }
            return data.slice(newPosition, data.length() - newPosition);
        }