Mmh Rick, have no immediate input here beside that the problem och deciding if a relationship exists between two nodes is a reoccurring one. Would love to hear suggestions on how to fix that. Maybe have indexes on interesting relationships in certain useful cases? It is not exposed to python yet but the new indexing framework might help there, https://svn.neo4j.org/laboratory/components/lucene-index/trunk/ if you care to check it out?
Cheers, /peter neubauer COO and Sales, Neo Technology GTalk: neubauer.peter Skype peter.neubauer Phone +46 704 106975 LinkedIn http://www.linkedin.com/in/neubauer Twitter http://twitter.com/peterneubauer http://www.neo4j.org - Your high performance graph database. http://www.thoughtmade.com - Scandinavia's coolest Bring-a-Thing party. On Fri, Aug 27, 2010 at 8:19 PM, Rick Otten <rot...@windfish.net> wrote: > Changing this bit of code from my earlier example at least increments the > 'count' property on the relationships. I keep a list of all the ones I've > created and check them each time I'm requested to create a new one. > > It is probably not the most memory or processor efficient way to do it. > I'd love to hear other ideas for doing this in the neo4j python. > > > ########################################################################### > RelationshipList = [] > > ## Either create a relationship or increment the count on an existing one: > def create_activity_relationship(previousNode, currentNode): > > NodeList = [] > > for Node in isFollowedBy(previousNode): > > NodeList.append(Node) > > # If we don't already have a relationship, create one: > if currentNode not in NodeList: > > RelationshipList.append(previousNode.FollowedBy(currentNode, > count=1)) > > # Otherwise, increment the count on the relationship: > else: > for relationship in RelationshipList: > if (relationship.start == previousNode) and (relationship.end > == currentNode): > relationship['count'] = relationship['count'].intValue() + 1 > > > ########################################################################### >> Hello, >> >> I've been exploring the capabilities and possibilities of neo4j.py >> recently. It is pretty cool! Thanks! >> >> One thing I'm trying to avoid when building my new graph is duplicate >> relationships. Instead of creating the same relationship twice, I'd >> like to increment a 'count' property on the existing one. >> >> While it was pretty straightforward to to this for nodes by using an >> Index, I'm struggling to figure out how to do it efficiently for a >> relationship. >> >> I can tell if a relationship between the nodes exists by using a >> depth(1) traversal. Unfortunately this approach seems to be really slow >> when I'm adding even just a few thousand nodes and relationships. >> >> Because the traversal I'm using returns the nodes, I haven't been able >> to figure out how to get the existing relationship in a way that lets me >> increment the count property. >> >> Here is what I tried to do: >> >> ########################################################################### >> neo4j_db = neo4j.GraphDatabase( options.neo4jDB, >> classpath=[myClassPath], >> jvm=myJVM, >> heap_size=128) >> >> myNodeIndex = neo4j_db.index("mynodes", create=True) >> >> ## Either create a new node, or increment the count on the existing node: >> def create_my_node(nodeName): >> >> my_node = myNodeIndex[nodeName] >> >> if not my_node: >> my_node = neo4j_db.node(name=nodeName, count=0) >> myNodeIndex[nodeName] = my_node >> >> my_node['count'] = my_node['count'].intValue() + 1 >> >> return my_node >> >> ## Traversal class used to check if a relationship already exists: >> class isFollowedBy(neo4j.Traversal): >> >> types = [ neo4j.Outgoing.FollowedBy ] >> order = neo4j.DEPTH_FIRST >> stop = neo4j.StopAtDepth(1) >> >> def isReturnable(self, position): >> return (not position.is_start >> and position.last_relationship.type == 'FollowedBy') >> >> ## Either create a new relationship, or increment the count on the >> existing one: >> # ** (This is really slow, and the increment doesn't work.)** >> def create_my_relationship(previousNode, currentNode): >> >> NodeList = [] >> >> for Node in isFollowedBy(previousNode): >> >> NodeList.append(Node) >> >> # If we don't already have a relationship, create one: >> if currentNode not in NodeList: >> >> previousNode.FollowedBy(currentNode, count=1) >> >> # Otherwise, increment the count on the relationship: >> else: >> for relationship in previousNode.relationships('OUTGOING'): >> if relationship.getOtherNode(previousNode) == currentNode: >> relationship['count'] = relationship['count'].intValue() + >> 1 >> >> >> >> >> -- >> Rick Otten >> rot...@windfish.net >> O=='=+ >> >> >> _______________________________________________ >> Neo4j mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user >> > > > -- > Rick Otten > rot...@windfish.net > O=='=+ > > > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
