TopSuggestDocs.merge, documented as analogous to TopDocs.merge, sizes its priority queue by topN before it reads any shard, so merging with topN = Integer.MAX_VALUE ('all') throws IllegalArgumentException 'maxSize must be >= 0 and < 2147483631' even for 3 hits or no shards (NegativeArraySizeException before 7.5.0), while TopDocs.merge returns the hits; a large legal topN allocates topN + 1 queue slots for a few hits

Finding LFV-1002Area: suggest / document suggester: TopSuggestDocs.merge (merging per-shard suggestion results)Priority: lowImpact: crashNovelty: new

Finding page for LFV-1002

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

What it shows

You collect suggestions from two index shards (for example SuggestIndexSearcher.suggest(query, 5, false) on each, giving 3 and 2 hits) and combine them with TopSuggestDocs.merge(Integer.MAX_VALUE, shards) to keep them all; its javadoc calls it 'Analogous to TopDocs#merge(int, TopDocs[])' and sets no bound on topN, so you expect the 5 hits that merge(10, ...) returns and that TopDocs.merge(Integer.MAX_VALUE, ...) returns for ordinary hits. Instead merge throws IllegalArgumentException 'maxSize must be >= 0 and < 2147483631; got: 2147483647', even for a single empty shard, because it creates its PriorityQueue with topN slots before it looks at any shard (TopSuggestDocs.java:116-117), while TopDocs.merge sizes its queue by the number of shards and its result by the hits it received. Below that limit, a large topN such as 10^8 makes merge allocate topN + 1 slots for a handful of hits.

The test shows that TopSuggestDocs.merge of two one-hit shards with topN = Integer.MAX_VALUE ("all hits") throws, because it sizes its PriorityQueue by topN before it reads any shard (TopSuggestDocs.java:117).

Expected vs actual

Expected: the 2 merged hits, as with topN = 10 and as TopDocs.merge, its documented analogue, returns. Actual (-ea and -da): IllegalArgumentException "maxSize must be >= 0 and < 2147483631; got: 2147483647".

Files

Run it

# 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=$CP:$LUCENE/lucene/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$CP:$LUCENE/lucene/suggest/build/libs/lucene-suggest-$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.search.suggest.document.TestTopSuggestDocsMergeAllHits

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

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Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.