Cool, Mattias. I just ran into that requirement again today. This is also another good case for the cached/persisted "number of relationships" counter on a node that has also been discussed. It would enable the optimization to occur automatically.
Another API function that would be useful (though it is also easy to implement) is one that automatically deletes all relationships for a node, then deletes the node, since that is the required path of action anyway to delete a node. -----Original Message----- From: user-boun...@lists.neo4j.org [mailto:user-boun...@lists.neo4j.org] On Behalf Of Mattias Persson Sent: Sunday, April 25, 2010 3:52 PM To: Neo4j user discussions Subject: [Neo] Checking if relationship exists between two nodes As you all (probably) know the Neo4j API has no method Node#hasRelationshipTo(Node otherNode) and to find out such a thing could potentially be slow if both the nodes has many relationships (of the type/direction you want to check). I just created a utility for that which starts to iterate from the node (of the two) that the developer thinks/knows has the least relationships. If a certain amount of relationships have been iterated and not yet found a new thread is spawned which starts to iterate from the other node in the opposite direction. The method will return as soon as the first thread finds a match. I'd guess that's the fastest way currently to do that. The next level of this would be to add indexing for relationships (which is an upcoming feature) and go via that instead. So the code may look like: (it's in the neo4j-utils component) GraphDatabaseUtil graphDbUtil = new GraphDatabaseUtil( graphDb ); boolean exists = graphDbUtil.relationshipExistsBetween( node1, node2, MyRelTypes.MY_TYPE, Direction.OUTGOING ); -- Mattias Persson, [matt...@neotechnology.com] Hacker, Neo Technology www.neotechnology.com _______________________________________________ Neo mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ Neo mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
