JoinUtil's numeric join on Float or Double throws 'values are out of order' when the from side has two or more distinct negative values

Finding LFV-217Area: join / JoinUtil numeric (point-based) query-time joinPriority: mediumImpact: crashNovelty: 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 build JoinUtil.createJoinQuery("fromF", false, "toF", Float.class, fromQuery, searcher, ScoreMode.None) where the from documents store -1 and -2 in a FloatDocValuesField and the to documents index FloatPoint -1, -2 and 3, and expect a query that matches the two to documents with -1 and -2, because the javadoc lists Float and Double as supported numeric types with no sign restriction. Instead createJoinQuery throws IllegalArgumentException 'values are out of order: saw [40 7f ff ff] before [3f ff ff ff]' (that is, -1 before -2; releases before 10.4.0 show an UnsupportedOperationException raised while that message is built), and Double and every scoring ScoreMode fail the same way. The cause is that JoinUtil sorts the collected Float/Double join values as raw IEEE bits in signed-long order, which for negative numbers is the reverse of numeric order, and streams them in that order into PointInSetQuery / PointInSetIncludingScoreQuery, which require strictly ascending points.

The test shows that JoinUtil's numeric join on Float.class (ScoreMode.None) fails when the from side has the two negative values -1 and -2 (FloatDocValuesField).

Expected vs actual

Expected: a join query that counts the 2 documents with FloatPoint -1 and -2. Actual (-ea and -da): IllegalArgumentException values are out of order: saw [40 7f ff ff] before [3f ff ff ff].

Files

src/org/apache/lucene/search/join/TestNumericJoinNegativeFloats.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=$CP:$LUCENE/lucene/join/build/libs/lucene-join-$V.jar
CP=$CP:$LUCENE/lucene/queries/build/libs/lucene-queries-$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.join.TestNumericJoinNegativeFloats

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.