DocValuesRewriteMethod's Weight#matches looks the matched terms up in the postings, so on a doc-values-only field it returns null for every hit of newSlowSetQuery or any DOC_VALUES_REWRITE query (highlights are silently lost, and a MUST_NOT clause of this kind fails open in Weight#matches)
Finding LFV-243Area: core / search: MultiTermQuery rewrite methods (DocValuesRewriteMethod, DOC_VALUES_REWRITE) and the Matches API (Weight#matches)Priority: mediumImpact: 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 keep a keyword field as doc values only, filter on it with SortedSetDocValuesField.newSlowSetQuery or a PrefixQuery with DOC_VALUES_REWRITE (DocValuesRewriteMethod says it 'can be used to perform these queries against an unindexed docvalues field'), and expect Weight#matches to return non-null Matches (MATCH_WITH_NO_TERMS) for every hit, as its javadoc promises for DocValues queries and as newSlowExactQuery on the same field does. Instead matches() looks the matched terms up in the field's postings, which do not exist, so it returns null for every hit; for +body:fruit #tags:(banana) the UnifiedHighlighter with default settings returns 'a ripe fruit in a basket' with no highlighted term, while the same query with newSlowRangeQuery as the filter highlights '<b>fruit</b>'. As a MUST_NOT clause the same null makes Weight#matches non-null for documents the clause excludes; hits, counts and scores stay correct.
The test shows that Weight#matches of SortedSetDocValuesField.newSlowSetQuery (DOC_VALUES_REWRITE) on a doc-values-only field returns null for a hit, because it looks the term up in postings that do not exist.
Expected vs actual
Expected non-null Matches (MATCH_WITH_NO_TERMS, per the Weight#matches javadoc) for hit doc 0; actual: null, 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=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar # test-framework dependencies (Maven Central)
CP=$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.TestDocValuesSetQueryMatchesGradle 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.