The frozen-FieldType validation cache (#15886) keys a field on its first value's type, so for a field built from several field types a later document skips the per-field schema check (or is checked against stale state after a rejected addBatch), depending on value order, flushes and earlier operations
Finding LFV-118Area: index / IndexingChain per-field schema validation (frozen-FieldType cache)Priority: mediumImpact: wrong errorNovelty: new
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 documents whose field id is a StringField plus a SortedDocValuesField, adding the StringField first, and then a document that has only the StringField. You expect IllegalArgumentException, as Lucene's per-field consistency rule (LUCENE-9334, MIGRATE.md) requires, as 9.0-10.4 do, and as main still does when the doc-values value comes first, the type is an unfrozen copy, or a flush comes in between. Instead the document is accepted, because the frozen-FieldType cache added in 10.5.0 (#15886) caches the first value's type after the union of all the document's values was validated and then skips the check for every later document whose first value has that type; on the same fast path the schema state is not rebuilt, so after a rejected addBatch a valid StringField + StoredField document fails with 'index options: expected DOCS, but it has NONE'.
The test shows that after a document whose field id is a StringField followed by a SortedDocValuesField, the frozen-FieldType cache lets a second document with only the StringField id skip the per-field schema check (TestFrozenTypeCacheMultiTypeField#testDocumentWithoutDocValuesRejected).
Expected vs actual
Expected IllegalArgumentException (the LUCENE-9334 per-field consistency rule; 10.4 and main with the other value order reject it); actual: the document is accepted (Expected exception IllegalArgumentException but no exception was thrown), with -ea and -da.
Files
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.TestFrozenTypeCacheMultiTypeFieldGradle 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: indexingchain-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 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.