Intervals.before(source, reference) treats a source interval at position 0 as before a reference interval that also starts at position 0, so for example before(york, york) matches the one-word document 'york'

Finding LFV-293Area: queries / intervals (Intervals.before, OffsetIntervalsSource PRECEDING)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-293

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

What it shows

You search with Intervals.before(source, reference), for example before(term new, phrase(new, york)) on the text 'new york', or before(term york, term york) on the one-word text 'york'. You expect no match, because the javadoc says before 'Returns intervals from the source that appear before intervals from the reference' and nothing comes before the first word. Instead both documents match: before() is built from a helper that places a pseudo-interval one position before each reference match, and for a reference at position 0 the helper clamps that position to 0 instead of producing nothing, so a source at position 0 counts as 'before' it; prepend one unrelated word and the same text correctly stops matching.

The test shows that Intervals.before(york, york) matches the one-word document "york", so a term at position 0 counts as before a reference that also starts at position 0.

Expected vs actual

Expected 0 hits (nothing comes before the only word); actual: 1 hit (expected:<0> but was:<1>), with -ea and -da.

Files

• src/org/apache/lucene/queries/intervals/TestBeforeAtFirstPosition.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/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.queries.intervals.TestBeforeAtFirstPosition

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.