IndexWriter on main: a push of the buffered deletes that finds nothing left to freeze leaks one flush-ticket count, so for the rest of the writer's life every NRT reader reports isCurrent() == false, even right after commit(), while openIfChanged() returns null

Finding LFV-1043Area: index / IndexWriter NRT (DocumentsWriterFlushQueue flush-ticket count, DocumentsWriter.anyChanges)Priority: lowImpact: minorNovelty: new

Finding page for LFV-1043

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

What it shows

Several threads add and delete documents on one IndexWriter; afterwards you commit and open an NRT reader without changing anything else, and you expect that reader's isCurrent() to be true, as it is on 10.5.2. Instead, if two threads pushed the buffered deletes at the same time and the second push found nothing left to freeze, DocumentsWriterFlushQueue.addTicket counted a ticket it never queued and never gives the count back (a regression of #15134). From then on DocumentsWriter.anyChanges() is always true, so every NRT reader of the writer, also ones opened after later commits, reports isCurrent() == false while openIfChanged() returns null.

Expected vs actual

• Expected: hasTickets() is false after a null ticket, as on 10.5.2.
• Actual: hasTickets() stays true: AssertionError at TestDocumentsWriterFlushQueue.java:27, with assertions on and off.

Files

• src/org/apache/lucene/index/TestDocumentsWriterFlushQueue.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 e1faeba08bde: 1 test(s) run, 1 failed (testNullTicketDoesNotLeaveTicketCount).
• 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.TestDocumentsWriterFlushQueue

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).

Files shown on the finding page

• TestDocumentsWriterFlushQueue.java

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.