DisjunctionMaxQuery with tie-breaker 0 scores NaN instead of +Infinity when two matching disjuncts score +Infinity (Infinity + Infinity * 0), so COMPLETE-mode collection, some BooleanQuery nestings and explain() disagree with the default top-k search (since 1.9)
Finding LFV-1124Area: core / search (DisjunctionMaxQuery: DisjunctionMaxScorer.score and DisjunctionMaxWeight.explain)Priority: lowImpact: minorNovelty: new
AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.
What it shows
You index one document with two FeatureField features a = b = 1e38 and search DisjunctionMaxQuery([FeatureField.newLinearQuery(f, a, 64), newLinearQuery(f, b, 64)], tieBreakerMultiplier 0) with a collector that counts every hit (TopScoreDocCollectorManager(1, Integer.MAX_VALUE)). Each disjunct scores 64 * 1e38 = +Infinity, so with tie 0 you expect the maximum, +Infinity, which is what the default search(q, n) and DisjunctionMaxScorer.getMaxScore give. You get NaN, with no error: DisjunctionMaxScorer.score moves the first +Infinity into the sum of the other scores and returns Infinity + Infinity * 0 = NaN, and explain() and some BooleanQuery nestings give NaN too, so the same document's score and rank depend on how the query is executed.
Expected vs actual
- Expected: The hit scores +Infinity, the larger of the two clause scores (what
search(q, 10)returns). - Actual: The hit scores NaN:
AssertionError: expected:<Infinity> but was:<NaN>, with assertions on and off.
Files
Run it
- Tested on Lucene main 5adff78bb168 (2026-11-02): reproduced.
- How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
- Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.
# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar # JUnit Platform console launcher (Maven Central)
javac -d classes -cp "$CP" $(find src -name '*.java')
# run 1: assertions off (production-like), seed DEADBEEF
java -da -dsa -Dtests.asserts=false -Xmx1g --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -XX:ActiveProcessorCount=2 -Dtests.seed=DEADBEEF \
-cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
execute --select-class org.apache.lucene.search.TestDisjunctionMaxTieZeroInfiniteScoresGradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).
Files shown on the finding page
Feedback
Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.
Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.