A MUST_NOT clause next to a scoring ToParentBlockJoinQuery is checked against child documents instead of parents, so excluded parents are returned, and the search throws when a parent/child block straddles a 4096-doc window

Finding LFV-222Area: join / block join (ToParentBlockJoinQuery.BlockJoinBulkScorer) x search / BooleanQuery MUST_NOT bulk scoring (ReqExclBulkScorer, #16669)Priority: highImpact: silent wrong resultsNovelty: known upstream

Finding page for LFV-222

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

What it shows

You index parent/child blocks and search BooleanQuery(MUST ToParentBlockJoinQuery(skill:java, parentsFilter, ScoreMode.Avg), MUST_NOT status:hidden), expecting only the parents that are not hidden, which is what count() of the same query and ScoreMode.None return. Instead, on main the hidden parent p2 comes back for Avg, Max, Min and Total ([p1, p2] instead of [p1]); a MUST_NOT clause that matches only child documents (MUST_NOT skill:java) removes both parents ([] instead of [p1, p2]); and in a 6,000-doc segment where a block straddles doc 4096 the search throws AssertionError in ReqExclBulkScorer$WindowBits.get with -ea and ArrayIndexOutOfBoundsException (index -1) with -da. The cause is that since #16669 ReqExclBulkScorer folds the MUST_NOT matches of each 4096-doc window into a bit set that it passes to the required clause as acceptDocs, and the join's BlockJoinBulkScorer forwards that acceptDocs unchanged to its child scorer (ToParentBlockJoinQuery.java:541), so the exclusions are tested on child doc IDs, some of them below the window, and never on the parents it collects.

The test shows that a MUST_NOT clause next to a scoring ToParentBlockJoinQuery is checked against child documents instead of parents, so an excluded parent is returned (TestBlockJoinMustNotExcludesParent#testMustNotExcludesParent).

Expected vs actual

Expected search(q, 10) to return only p1 (as count(q) = 1 does); actual [p1, p2] (expected:<[p1]> but was:<[p1, p2]>), with -ea and -da.

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/join/build/libs/lucene-join-$V.jar
CP=$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 5EED0222
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=5EED0222 \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.search.join.TestBlockJoinMustNotExcludesParent

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).

Feedback

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Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.