AnalyzingSuggester and FuzzySuggester compute the top-N queue depth num * maxAnalyzedPathsForOneInput in int, so with a synonym (token graph) analyzer a large num wraps it: lookup silently returns too few suggestions and skips higher-weighted ones, or throws NoSuchElementException, and with assertions on lookup(key, false, Integer.MAX_VALUE) typically fails 'assert completions.isComplete'

Finding LFV-1003Area: suggest / analyzing: AnalyzingSuggester and FuzzySuggester lookup (FST top-N queue depth)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-1003

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

What it shows

You build an AnalyzingSuggester (or FuzzySuggester) whose index-time analyzer expands one entry into several analyzed forms, for example a SynonymGraphFilter that also indexes 'lucene' as 'search' and 'find', and call lookup("luc", false, num) with a large num; num is documented as the 'maximum number of results to return', so you expect the 8 suggestions that num = 1000 returns. Instead the search's queue depth num * maxAnalyzedPathsForOneInput is computed in int (AnalyzingSuggester.java:786) and wraps: with 3 paths and num = 1431655766 it becomes 2, the top-N search prunes paths it still needs, and lookup returns [lucas, lucifer, lucid] with no error, skipping the higher-weighted luck, lucent and lucerne (FuzzySuggester: 5 of 8), and with 4 paths and num = 2^30 it becomes 0 and lookup throws NoSuchElementException. With assertions enabled, lookup(key, false, Integer.MAX_VALUE) on a suggester with 2 or more paths typically fails 'assert completions.isComplete' (:824), although the same call without assertions returns the right list.

The test shows that AnalyzingSuggester.lookup with num = 1431655766 and an entry that has 3 analyzed paths (synonyms) silently returns too few suggestions, because the queue depth num * 3 overflows int to 2.

Expected vs actual

Expected: all 3 matches [ad, ac, ab]. Actual with -da: [ad, ac]. With -ea the class's own assert completions.isComplete (AnalyzingSuggester.java:824) fails first.

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.analyzing.TestAnalyzingSuggesterLargeNum

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: suggester-lookup-num-overflow-and-presize

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.