presto-orc/src/main/java/io/prestosql/orc/writer/StructColumnWriter.java/StructColumnWriter/reset
class StructColumnWriter:    @Override
    public void reset()
    {
        closed = false;
        presentStream.reset();
        structFields.forEach(ColumnWriter::reset);
        rowGroupColumnStatistics.clear();
        nonNullValueCount = 0;
    }