A persistent Monitor query index written before 10.3.0 keeps missing matches after an upgrade to 10.3.0 or later, until every query is registered again (the #14886 fix covers only indexes written from 10.3.0 on)

Finding LFV-1115Area: monitor / persistent query index (WritableQueryIndex, ReadonlyQueryIndex, QueryDecomposer)Priority: mediumImpact: silent wrong resultsNovelty: known upstream

AI-assisted finding, reproduced on Lucene main but not yet independently re-verified, and not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You register the query f:alpha OR f:beta in a persistent Monitor on 10.2.2, upgrade to 10.3.0 or later, open the same query index and match a document whose field f is 'alpha'; you expect the query to match, as it does on a freshly registered Monitor. It does not, with no error: the stored branch documents keep the 10.2.2 writer's hash order of the branches, which follows that JVM's hash seed (in the repro's index, cache ids q_0 = beta, q_1 = alpha), while 10.3.0 and later rebuild the cache in clause order (q_0 = alpha, q_1 = beta), so the presearcher selects branch q_1 and the Monitor runs f:beta on the document.

Expected vs actual

Files

Run it

# 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/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$CP:$LUCENE/lucene/backward-codecs/build/libs/lucene-backward-codecs-$V.jar
CP=$CP:$LUCENE/lucene/memory/build/libs/lucene-memory-$V.jar
CP=$CP:$LUCENE/lucene/monitor/build/libs/lucene-monitor-$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)

# required fixture monitor-index-10.2.2.zip, written by the Lucene 10.2.2 release: the lucene-core, lucene-monitor, lucene-memory and lucene-analysis-common 10.2.2 jars (Maven Central)
FCP=lucene-core-10.2.2.jar:lucene-monitor-10.2.2.jar:lucene-memory-10.2.2.jar:lucene-analysis-common-10.2.2.jar
javac -d fixture-classes -cp "$FCP" fixture-src/WriteMonitorIndex.java
java -Dtests.seed=CAFEBABE -cp "fixture-classes:$FCP" WriteMonitorIndex fixture-index
mkdir -p src/org/apache/lucene/monitor && (cd fixture-index && rm -f write.lock && zip -q -X ../src/org/apache/lucene/monitor/monitor-index-10.2.2.zip *)

javac -d classes -cp "$CP" $(find src -name '*.java')

# run 1: assertions off (production-like), seed DEADBEEF
java -da -dsa -Dtests.asserts=false -Xmx1g --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -XX:ActiveProcessorCount=2 -Dtests.seed=DEADBEEF \
     -cp "classes:src:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.monitor.TestMonitorIndexFromOlderRelease

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).

1 other file(s) of the recorded repro are not exported.

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.