presto-orc/src/main/java/io/prestosql/orc/OrcRecordReader.java/OrcRecordReader/getStreamReaderRetainedSizeInBytes
class OrcRecordReader:    @VisibleForTesting
    long getStreamReaderRetainedSizeInBytes()
    {
        long totalRetainedSizeInBytes = 0;
        for (ColumnReader column : columnReaders) {
            if (column != null) {
                totalRetainedSizeInBytes += column.getRetainedSizeInBytes();
            }
        }
        return totalRetainedSizeInBytes;
    }