MatchHighlighter.highlight(topDocs, q1, q2, ...) silently drops the highlights of every field that only the second or a later query matches: each document keeps only the stored field values of the first query's MatchRegionRetriever, which loads just the fields that first query affects (regression in 10.0.0)
Finding LFV-595Area: highlighter / matchhighlight: MatchHighlighter multi-query highlighting (DocHit field values on top of MatchRegionRetriever's per-query stored-field loading)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 pass several queries to MatchHighlighter.highlight(topDocs, q1, q2), for example title:foo and body:bar for a document whose title is 'foo' and whose body is 'bar'; the class's own test passes the sub-clauses of the search query this way to give each query its own markers. You expect both fields to be highlighted, exactly as highlight(topDocs, title:foo OR body:bar) returns them: {title=[>foo<], body=[>bar<]}. Instead you get only {title=[>foo<]} (only {body=[>bar<]} with the queries swapped), with no error, because each document keeps only the stored fields that the first query's retriever loaded; 9.x returned both fields.
The test shows that MatchHighlighter.highlight(topDocs, title:foo, body:bar) on one document (title "foo", body "bar") drops the field that only the second query matches.
Expected vs actual
Expected: {title=[>foo<], body=[>bar<]}; actual (-ea and -da): {title=[>foo<]}, because the DocHit keeps only the field values loaded by the first query's MatchRegionRetriever (MatchHighlighter.java:173, :242).
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/highlighter/build/libs/lucene-highlighter-$V.jar
CP=$CP:$LUCENE/lucene/memory/build/libs/lucene-memory-$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.matchhighlight.TestMatchHighlighterMultiQueryFieldsGradle 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.