Geo3dDistanceCalculator.within returns the opposite of 'distance <= limit' for every finite distance, so the default distance calculator of the Geo3d spatial context answers every within() call backwards

Finding LFV-674Area: spatial-extras / spatial4j bridge to spatial3d (Geo3dDistanceCalculator.within, the default DistanceCalculator that Geo3dSpatialContextFactory installs)Priority: lowImpact: minorNovelty: new

Finding page for LFV-674

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

What it shows

You create a spatial context with Geo3dSpatialContextFactory and ask its distance calculator whether the point (1, 0) is within 10 degrees of (0, 0), with ctx.getDistCalc().within(from, 1, 0, 10), and expect true: distance() returns 1.0 degree, and the spatial4j DistanceCalculator contract says within() is true when the distance is <= the limit. Instead it returns false, and within(from, 50, 0, 10) returns true although the distance is 50 degrees. The method body is 'return (distance < distance(from, toX, toY));', the exact negation of the contract, so every answer with a finite distance is inverted, including within(p, p, 0).

The test shows that Geo3dDistanceCalculator.within, the default DistanceCalculator of a Geo3d spatial context, returns the opposite of spatial4j's "distance <= limit" contract.

Expected vs actual

Expected: within((0, 0), 1, 0, 10) is true, because the point is 1 degree away. Actual (-ea and -da): false.

Files

• src/org/apache/lucene/spatial/spatial4j/TestGeo3dDistanceCalculatorWithin.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=$CP:$LUCENE/lucene/spatial-extras/build/libs/lucene-spatial-extras-$V.jar
CP=$CP:$LUCENE/lucene/spatial3d/build/libs/lucene-spatial3d-$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.spatial.spatial4j.TestGeo3dDistanceCalculatorWithin

The module(s) spatial-extras also need their third-party runtime jars; ./gradlew -p lucene/<module> dependencies lists them.

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