MultiFieldQueryParser under AND treats clause i of every field's analyzed BooleanQuery as term position i and requires each group, so fields whose analyzers tokenize the same text differently lose (and sometimes gain wrong) matches (released since 6.2.0, default settings since 7.0.0), and since #16446 (10.6.0) graph-phrase alternatives such as a multi-word synonym are required together

Finding LFV-319Area: queryparser / classic MultiFieldQueryParser (getFieldQuery(String,String,boolean) per-field clause grouping and getMultiTermPositionQuery; core util/QueryBuilder graph phrases)Priority: mediumImpact: silent wrong resultsNovelty: new

Finding page for LFV-319

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You search the fields title and body with MultiFieldQueryParser under AND_OPERATOR and expect what its class javadoc promises: every query term must appear, in any field, so adding a field never loses a document that QueryParser on one of those fields finds. Instead getFieldQuery takes clause i of each field's analyzed BooleanQuery as 'term position i' and requires every such group: with title tokenized on whitespace and body on letters, 'wi-fi router' becomes +(title:wi-fi body:wi) +(title:router body:fi) +(body:router), which misses a document titled 'wi-fi router' and matches one with title 'router' and body 'wi router' (released since 6.2.0, default settings since 7.0.0; since #16446 the single word 'wi-fi' loses the match too). Since #16446 (in 10.6.0), with autoGeneratePhraseQueries and the multi-word synonym 'guinea pig' -> 'cavy', 'guinea-pig' becomes +(body:"guinea pig") +(body:cavy), so even MultiFieldQueryParser over body alone finds nothing where QueryParser(body) finds the document.

The test shows that under AND with autoGeneratePhraseQueries, MultiFieldQueryParser over the single field body turns the synonym alternatives of guinea-pig ("guinea pig" OR cavy) into two required clauses.

Expected vs actual

Expected: 1 hit, the same as QueryParser("body") (body:"guinea pig" body:cavy). Actual: +(body:"guinea pig") +(body:cavy) finds 0 hits.

Files

• src/org/apache/lucene/queryparser/classic/TestMultiFieldQueryParserSynonymGraph.java (JUnit test)

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:$LUCENE/lucene/queries/build/libs/lucene-queries-$V.jar
CP=$CP:$LUCENE/lucene/queryparser/build/libs/lucene-queryparser-$V.jar
CP=$CP:$LUCENE/lucene/sandbox/build/libs/lucene-sandbox-$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.queryparser.classic.TestMultiFieldQueryParserSynonymGraph

The 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).

Formal models and scripts this finding's part of the hunt used: queryparser-classic

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.