Incheonkirin opened a new pull request, #16409:
URL: https://github.com/apache/lucene/pull/16409

   ### Description
   
   `FilteredHnswGraphSearcher` can stop before exploring a candidate whose 
score is equal to the current result floor, and it rejects neighbors whose 
score is exactly `Math.nextUp(results.minCompetitiveSimilarity())`.
   
   The latter score is strictly better than the current minimum and is 
competitive. The base `HnswGraphSearcher` already handles both boundaries:
   
   - #14249 changed neighbor admission from `>` to `>=` because a score equal 
to `Math.nextUp(minCompetitiveSimilarity)` is better.
   - #14366 allows one candidate equivalent to the current minimum to be 
explored, while preventing the degenerate equal-score case from expanding 
without bound.
   
   The filtered searcher was added before those follow-ups and retained the 
earlier boundary behavior. This change applies the same contract to the 
filtered path:
   
   - explore one candidate equivalent to the current minimum;
   - admit a neighbor at `minAcceptedSimilarity`;
   - gate the scored batch on `maxScore > results.minCompetitiveSimilarity()`, 
the same bound the base searcher uses;
   - reset the one-equivalent guard when collection raises the minimum.
   
   ### Regression tests
   
   Both tests call `FilteredHnswGraphSearcher` directly, so they do not depend 
on the filtered-search dispatch heuristic.
   
   The first test uses a four-node graph with two accepted nodes and `k=1`. The 
entry node scores `0.5`; its accepted neighbor scores `Math.nextUp(0.5)`. 
Before this change, filtered HNSW returns the `0.5` entry and never considers 
the strictly better neighbor. After the change, it returns the neighbor.
   
   The second test searches a chain where every node has the same score and 
asserts that visitation stays bounded: one candidate tied with the current 
minimum may be explored, then the search stops.
   
   ### Validation
   
   - regression tests: fail on current main, pass with the change
   - `./gradlew :lucene:core:check` passes: 8,534 tests, 307 skipped
   
   Related history: #14160, #14215, #14249, #14366, #15500.
   


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