[Backport 2.x] Fix negative scores returned from multi_match query with cross_fields
#13983
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…lds` (opensearch-project#13829) Under specific circumstances, when using `cross_fields` scoring on a `multi_match` query, we can end up with negative scores from the inverse document frequency calculation in the BM25 formula. Specifically, the IDF is calculated as: ``` log(1 + (N - n + 0.5) / (n + 0.5)) ``` where `N` is the number of documents containing the field and `n` is the number of documents containing the given term in the field. Obviously, `n` should always be less than or equal to `N`. Unfortunately, `cross_fields` makes up a new value for `n` and tries to use it across all fields. This change finds the (nonzero) value of `N` for each field and uses that as an upper bound for the new value of `n`. Signed-off-by: Michael Froh <froh@amazon.com> --------- Signed-off-by: Michael Froh <froh@amazon.com> (cherry picked from commit fffd101)
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## 2.x #13983 +/- ##
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+ Coverage 71.28% 71.31% +0.02%
- Complexity 60145 61322 +1177
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Files 4957 5039 +82
Lines 282799 288411 +5612
Branches 41409 42135 +726
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+ Hits 201591 205676 +4085
- Misses 64189 65398 +1209
- Partials 17019 17337 +318 ☔ View full report in Codecov by Sentry. |
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…lds` (opensearch-project#13829) (opensearch-project#13983) Signed-off-by: kkewwei <kkewwei@163.com>
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Manual backport of #13829
Under specific circumstances, when using
cross_fieldsscoring on amulti_matchquery, we can end up with negative scores from the inverse document frequency calculation in the BM25 formula.Specifically, the IDF is calculated as:
where
Nis the number of documents containing the field andnis the number of documents containing the given term in the field. Obviously,nshould always be less than or equal toN.Unfortunately,
cross_fieldsmakes up a new value fornand tries to use it across all fields.This change finds the (nonzero) value of
Nfor each field and uses that as an upper bound for the new value ofn.Signed-off-by: Michael Froh froh@amazon.com
Signed-off-by: Michael Froh froh@amazon.com
(cherry picked from commit fffd101)
Related Issues
Resolves #[Issue number to be closed when this PR is merged]
Check List
New functionality includes testing.All tests passNew functionality has been documented.New functionality has javadoc addedAPI changes companion pull request created.Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)Public documentation issue/PR createdBy submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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