Extracting arrangement from `threshold_total`

Hi @frankmcsherry,

You mentioned several times in the past that threshold and threshold_total operators internally construct arrangements that can in principle be extracted and reused just like any other DD arrangement. I would like to implement this idea and was hoping you could point me towards the correct API. At the moment I have the following code in DDlog:

    my_collection.threshold_total(|_, c| if c.is_zero() { 0 } else { 1 })
                .map(|k| (k, ())).arrange()

Is my understanding correct that the arrangement created by the arrange operator above is a duplicate of the one built by threshold_total internally? If so, what would be the best way to extract this internal arrangement?

Thanks!

Start with the threshold and threshold_total operators and compare their internal arrangements with the arrangement produced by arrange in the shown DDlog chain. Determine the API for extracting and reusing the internal arrangement; done means the duplicate arrangement is avoided and the extracted arrangement can be reused as described.