how are manysearch results ordered, and can we threshold num results returned?

[bluegenes]

Had a question on whether manysearch results are ordered by best hit, and whether we could add a threshold parameter to return only the top n results.

I think:

• non-rocksdb manysearch are ordered by the order in the database, not sorted by best hit.
• rocksdb manysearch uses db.counter_for_query, which I think returns the best hits first?
  https://github.com/sourmash-bio/sourmash/blob/latest/src/core/src/index/revindex/disk_revindex.rs#L284C7-L301
  counter .most_common implies to me that we get sorted results...

We would need sorted results in order to implement a threshold number of hits to return.

The was brought up in the context of speeding up search and downstream processing. Since we need to check all database entries in order to build a sorted list, I think any potential benefit would be small -- would only reduce writing (fewer results to write) and very slightly speed up downstream processing (fewer results to read)?

[ctb]

this way lies madness.

• consider adjusting search --threshold default value and how -n works sourmash#2169
• Small number of matches in search sourmash#2168

strong opinion: since it's (mostly) not computationally challenging to load the results in after, leave it as-is and have all limits on number of results applied AFTER.

(old bad design decisions => let's avoid that mess in the future 😆 )