SingletonSortedSetDocValues.intoBitSet does not refresh its cached ordinal, so nextOrd() returns an earlier document's ordinal and DocValuesRangeIterator.forOrdinalRange can return extra hits on single-valued segments

Finding LFV-091Area: index / doc values (single-valued SortedSetDocValues view, DocValuesRangeIterator)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-091

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

What it shows

You take the SortedSetDocValues of a segment whose documents have at most one value each (DocValues.getSortedSet and LeafReader#getSortedSetDocValues then return a single-valued wrapper), call intoBitSet(upTo, ...), and read nextOrd() for the document the iterator now sits on; or you pass that view to DocValuesRangeIterator.forOrdinalRange on a skip-indexed field and load the matches in bulk. You expect nextOrd() to describe the current document, as after the nextDoc() loop that the intoBitSet javadoc says it behaves exactly like, and the range iterator to mark only documents whose value is in range. Instead the wrapper's intoBitSet moves the inner iterator without refreshing its cached ordinal, so with two documents a and b nextOrd() on doc 1 returns a's ordinal, and forOrdinalRange for [b, b] also marks doc 8192, whose value is a.

The test shows that on the single-valued SortedSetDocValues view, intoBitSet moves the iterator to the next document but nextOrd() still returns the previous document's ordinal.

Expected vs actual

Expected: after nextDoc() (doc 0, "a") and intoBitSet(1, ...), the iterator is on doc 1 and nextOrd() is 1 ("b"). Actual: 0 (doc 0's "a").

Files

• src/org/apache/lucene/index/TestSingletonSortedSetIntoBitSetStaleOrd.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=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar   # test-framework dependencies (Maven Central)
CP=$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.index.TestSingletonSortedSetIntoBitSetStaleOrd

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

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.