presto-main/src/main/java/io/prestosql/operator/aggregation/minmaxby/SliceAndBlockPositionStateSerializer.java/SliceAndBlockPositionStateSerializer/writeFirstField
class SliceAndBlockPositionStateSerializer:    @Override
    void writeFirstField(BlockBuilder out, SliceAndBlockPositionValueState state)
    {
        firstType.writeSlice(out, state.getFirst());
    }