DoubleValuesSourceRescorer.rescore passes null scores to a DoubleValuesSource whose needsScores() is true, so rescoring with DoubleValuesSource.SCORES, an expression that reads _score or a FunctionScoreQuery.boostByValue source throws (AssertionError with -ea; NullPointerException or a misleading 'Unrecognized variable (_score)' RuntimeException with -da), while explain() on the same input returns normally

Finding LFV-334Area: core / search: DoubleValuesSourceRescorer.rescore and explain (score-dependent DoubleValuesSource)Priority: lowImpact: crashNovelty: new

Finding page for LFV-334

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You subclass DoubleValuesSourceRescorer to re-rank first-pass hits with a source that uses the query score, for example DoubleValuesSource.SCORES or the expression '_score * 2' with _score bound to SCORES, and expect rescore() to work as it does for any other source: the constructor accepts any DoubleValuesSource and documents no restriction. Instead rescore() calls source.getValues(ctx, null) for every source (DoubleValuesSourceRescorer.java:73), although DoubleValuesSource#getValues allows a null scores argument only when needsScores() is false and the SCORES javadoc says callers must not pass null, so it throws on the first hit: an AssertionError with -ea, and with -da a NullPointerException at line 74 or, for the expression, RuntimeException 'Unrecognized variable (_score) referenced in expression (_score * 2).'. explain() for the same rescorer, source and document returns a normal explanation, because it passes a placeholder 'DoubleValuesSource was not initialized with query scores' explanation instead of scores.

The test shows that DoubleValuesSourceRescorer.rescore with DoubleValuesSource.SCORES calls getValues(ctx, null) on a source whose needsScores() is true and fails on the first hit (one empty doc, MatchAllDocsQuery first pass).

Expected vs actual

Expected: rescored hits (or an IllegalArgumentException rejecting the source); actual: AssertionError from assert scores != null (DoubleValuesSource.java:361) with -ea, NullPointerException "values is null" (DoubleValuesSourceRescorer.java:74) with -da.

Files

• src/org/apache/lucene/search/TestDoubleValuesSourceRescorerScores.java (JUnit test)

Run it

• Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
• Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
• Recorded outcome of run 1 on Lucene main 645d4fe14a20: 1 test(s) run, 1 failed.
• 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 on, seed DEADBEEF
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.search.TestDoubleValuesSourceRescorerScores

Gradle 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).

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.