A deleteAll() that overlaps addIndexes clears the incoming fields from the writer's field schema, but addIndexes still publishes its segment, so a later document can give such a field another doc-values type and the committed index can no longer be opened by an IndexWriter

Finding LFV-1074Area: index / IndexWriter addIndexes vs deleteAll (writer-wide field schema, FieldInfos.FieldNumbers)Priority: mediumImpact: index unusableNovelty: known upstream

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

What it shows

One thread imports an index with IndexWriter.addIndexes while another thread calls deleteAll() on the same writer. You expect the outcome of one of the two orders: either the imported documents are deleted, or they stay and their fields keep their doc-values types, and in both cases the committed index opens again in a new IndexWriter. Instead deleteAll can clear the imported fields from the writer's schema while addIndexes still publishes the imported segment, so a later document can give an imported field another doc-values type, the commit succeeds, and the next new IndexWriter on that index throws IllegalArgumentException ('cannot change field "f" from doc values type=NUMERIC to inconsistent doc values type=SORTED').

Expected vs actual

• Expected: You expect the outcome of one of the two orders: either the imported documents are deleted, or they stay and their fields keep their doc-values types, and in both cases the committed index opens again in a new IndexWriter.
• Actual: deleteAll can clear the imported fields from the writer's schema while addIndexes still publishes the imported segment, so a later document can give an imported field another doc-values type, the commit succeeds, and the next new IndexWriter on that index throws IllegalArgumentException ('cannot change field "f" from doc values type=NUMERIC to inconsistent doc values type=SORTED').

Files

• src/org/apache/lucene/index/TestDeleteAllDuringAddIndexes.java (JUnit test)

Run it

• Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
• Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
• 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 off (production-like), seed DEADBEEF
java -da -dsa -Dtests.asserts=false --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -XX:ActiveProcessorCount=2 -Dtests.seed=DEADBEEF \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.index.TestDeleteAllDuringAddIndexes

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: deleteall-during-addindexes-keeps-imported-field-schema

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 2026-11-03. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.