presto-orc/src/main/java/io/prestosql/orc/writer/SliceDictionaryColumnWriter.java/SliceDictionaryColumnWriter/getBufferedBytes
class SliceDictionaryColumnWriter:    @Override
    public long getBufferedBytes()
    {
        checkState(!closed);
        if (directEncoded) {
            return directColumnWriter.getBufferedBytes();
        }
        // for dictionary columns we report the data we expect to write to the output stream
        return getIndexBytes() + getDictionaryBytes();
    }