A DirectoryReader opened with open(commit, minSupportedMajorVersion, leafSorter) forgets that minimum: isCurrent(), openIfChanged() and SearcherManager.maybeRefresh() throw IndexFormatTooOldException even on an unchanged index

Finding LFV-131Area: index / DirectoryReader reopen and isCurrent (expert old-index open)Priority: lowImpact: crashNovelty: new

Finding page for LFV-131

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

What it shows

You open an index whose segments come from an older Lucene major, which the default open refuses, through the expert DirectoryReader.open(commit, minSupportedMajorVersion, leafSorter) with a lower minimum, and it opens fine. With nothing committed since, you expect isCurrent() to return true and openIfChanged(reader) to return null, so that SearcherManager.maybeRefresh() does nothing. Instead all three throw IndexFormatTooOldException ('Index has segments derived from Lucene version 8.x and is not supported ...'), because the reader does not keep the minimum it was opened with and re-reads the commit with the default Version.MIN_SUPPORTED_MAJOR.

The test shows that a reader opened with the expert DirectoryReader.open(commit, minSupportedMajorVersion, leafSorter) (minimum 8) on an index whose segment is recorded as derived from Lucene 8.x cannot check itself: isCurrent() re-reads the commit with the default minimum (9).

Expected vs actual

Expected isCurrent() to return true on the unchanged index; actual: IndexFormatTooOldException ("Index has segments derived from Lucene version 8.x ... minimum supported: 9"), with -ea and -da.

Files

• src/org/apache/lucene/index/TestReopenBelowMinSupportedMajor.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.TestReopenBelowMinSupportedMajor

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.