This is a consistent behavior since a loong time. I think its a bug.
When you try finding a path from a node to itself using `astar` it throws
exception when it should just return null. To verify:
import org.neo4j.graphalgo.*;
import org.neo4j.graphdb.*;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.kernel.impl.util.FileUtils;
import java.io.File;
import java.io.IOException;
public class Main {
private static final String DB_PATH = "target/neo4j-hello-db";
GraphDatabaseService graphDb;
Node firstNode;
Relationship relationship;
private static enum RelTypes implements RelationshipType {
KNOWS, LIKE
}
public static void main(final String[] args) {
Main hello = new Main();
hello.clearDb();
hello.createDb();
hello.removeData();
hello.shutDown();
}
void createDb() {
clearDb();
// START SNIPPET: startDb
graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH);
registerShutdownHook(graphDb);
long l = System.currentTimeMillis();
Transaction tx = graphDb.beginTx();
try {
firstNode = graphDb.createNode();
PathFinder<WeightedPath> finder2 = GraphAlgoFactory.aStar(
PathExpanders.forTypeAndDirection(RelTypes.KNOWS,
Direction.BOTH),
new CostEvaluator<Double>() {
@Override
public Double getCost(Relationship relationship,
Direction direction) {
return 1d;
}
},
new EstimateEvaluator<Double>() {
@Override
public Double getCost(Node node, Node goal) {
return 1d;
}
});
WeightedPath path = finder2.findSinglePath(firstNode,
firstNode);
tx.success();
} finally {
tx.finish();
System.out.println(System.currentTimeMillis() - l);
}
}
private void clearDb() {
try {
FileUtils.deleteRecursively(new File(DB_PATH));
} catch (IOException e) {
throw new RuntimeException(e);
}
}
void removeData() {
Transaction tx = graphDb.beginTx();
try {
firstNode.getSingleRelationship(RelTypes.KNOWS,
Direction.OUTGOING).delete();
firstNode.delete();
tx.success();
} finally {
tx.finish();
}
}
void shutDown() {
System.out.println();
System.out.println("Shutting down database ...");
graphDb.shutdown();
}
private static void registerShutdownHook(final GraphDatabaseService
graphDb) {
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
graphDb.shutdown();
}
});
}
}
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