IndexSearcher throws IllegalArgumentException for any reader that contains a leaf with maxDoc() == 0 (for example a ParallelLeafReader with no sub-readers): the whole-segment LeafReaderContextPartition of that leaf fails a bounds check added for partition ranges (regression in 10.0.0)
Finding LFV-202Area: search / IndexSearcher slicing (LeafSlice, LeafReaderContextPartition)Priority: lowImpact: 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 an IndexSearcher over a reader that contains an empty leaf, for example new ParallelLeafReader() with no sub-readers, possibly next to a real index inside a MultiReader, and you expect searches to work and simply find no hits in the empty part, as they do on 9.12.3. Instead the searcher throws IllegalArgumentException 'minDocId is greater than than maxDoc: [0] > [0]', because slicing wraps every leaf in a whole-segment partition that starts at doc 0 and the partition constructor rejects a start that is not below the leaf's maxDoc(). In the repro, a MultiReader of a 5-doc index plus an empty ParallelLeafReader cannot be searched at all instead of returning 5 hits.
The test shows that new IndexSearcher(new ParallelLeafReader(true)) (a reader whose only leaf has maxDoc() == 0) cannot count a MatchAllDocsQuery.
Expected vs actual
Expected: count 0. Actual (-ea and -da): IllegalArgumentException minDocId is greater than than maxDoc: [0] > [0] from the whole-segment LeafReaderContextPartition.
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=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar # test-framework dependencies (Maven Central)
CP=$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.TestSearchZeroDocLeafGradle 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).
Formal models and scripts this finding's part of the hunt used: concurrent-collector-managers
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.