MRG: fix calculate_gather_stats threshold=0 bug

[bluegenes]

The error shows up when we try to calculate abundance info with a match_size of 0:

match: GCF_002819265.1 Choclo virus, match_size: 0, query_size: 273, query_trackabund: true
thread '<unnamed>' panicked at 'called `Option::unwrap()` on a `None` value', /home/ntpierce/sourmash/src/core/src/index/mod.rs:301:55

...we should never be trying to calculate statistics on match_size of 0, but the logic is currently match_size >= threshold.This includes a check to break if match_size is 0.

• fixes bug in calculate_gather_stats (rocksdb gather) #3051

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.78%. Comparing base (c7a1265) to head (16597b0).

Additional details and impacted files

@@           Coverage Diff           @@
##           latest    #3052   +/-   ##
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  Coverage   86.78%   86.78%           
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  Files         136      136           
  Lines       15523    15524    +1     
  Branches     2626     2626           
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+ Hits        13471    13472    +1     
  Misses       1751     1751           
  Partials      301      301           

Flag	Coverage Δ
hypothesis-py	25.53% <ø> (ø)
python	92.86% <ø> (ø)
rust	61.21% <100.00%> (+0.01%)	⬆️

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[bluegenes]

@sourmash-bio/devs ready for review!

[ctb]

Do we need a test? I'm ok if the answer is "no".

[bluegenes]

Do we need a test? I'm ok if the answer is "no".

We don't currently have tests for any of disk_revindex.rs (though I do have python tests for running + results in sourmash_plugin_branchwater), so adding one here would require a fair bit of setup. Can we put this to an issue to handle later? I can add a --threshold 0 test to sourmash_plugin_branchwater.

[ctb]

Do we need a test? I'm ok if the answer is "no".

We don't currently have tests for any of disk_revindex.rs (though I do have python tests for running + results in sourmash_plugin_branchwater), so adding one here would require a fair bit of setup. Can we put this to an issue to handle later? I can add a --threshold 0 test to sourmash_plugin_branchwater.

sure!

[luizirber]

We don't currently have tests for any of disk_revindex.rs (though I do have python tests for running + results in sourmash_plugin_branchwater), so adding one here would require a fair bit of setup.

Tests for disk_revindex are at the revindex module, because sourmash::index::revindex::RevIndex acts as an unified interface for disk and mem revindex. Tho only the disk one is really used =]