DrillDownQuery.clone() shares the per-dimension BooleanQuery.Builder objects with the original, so adding a value to a dimension both copies already constrain changes what the other copy matches (released since 4.7.0)
Finding LFV-367Area: facet / DrillDownQuery (clone() and the per-dimension BooleanQuery.Builder state)Priority: lowImpact: silent wrong resultsNovelty: 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 a DrillDownQuery that restricts color=red, call clone(), and add color=blue to the clone (or to the original), expecting the copy you did not touch to keep matching only red, as clone() and the upstream testClone imply. Instead both copies match red OR blue: the clone shares each dimension's internal BooleanQuery.Builder with its source, and add() on an existing dimension appends a SHOULD clause to that shared builder in place. Since 9.0 a copy that was already searched keeps a cached snapshot and shows the leaked value only after its own dimension changes again (then 3 hits where 2 are correct), and the two copies stay equals() with the same hashCode while they match different documents.
The test shows that DrillDownQuery.clone() shares the per-dimension BooleanQuery.Builder with the original, so adding color=blue to the clone also widens the original.
Expected vs actual
Expected: the original (color=red) still matches 1 of the 2 documents. Actual: 2 (expected:<1> but was:<2>, with -ea and -da).
Files
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/facet/build/libs/lucene-facet-$V.jar
CP=$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.facet.TestDrillDownQueryCloneIsolationThe module(s) facet also need their third-party runtime jars; ./gradlew -p lucene/<module> dependencies lists them.
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.