Two longs is certainly cheaper than a string. Two longs take 128 bit and are stored in the main record of the PropertyContainer, while a String would require a 64 bit "pointer" in the main record of the PropertyContainer, and an additional read in the String store where the string representation will take up 256 bits. So both memory-wise, as perfomance wise, it is better to store a UUID as two long values.
The main issue is something that needs a deeper fix than adding ID's. SortedTree now returns Nodes when traversing the tree. We should however return the KEY_VALUE Relationship to the indexed Node. Then IndexedRelationship.DirectRelationship can be created with that relationship as an argument. We get the Direction and the RelationshipType for free. Niels > Date: Thu, 8 Sep 2011 11:36:11 +1200 > From: [email protected] > To: [email protected] > Subject: Re: [Neo4j] Issues with IndexedRelationship > > Hi Niels, > > Sorry I didn't quite write the bit about (1) clearly enough. The problem is > that it presently throws an Exception where it shouldn't. > > This stems from IndexedRelationship.DirectRelationship: > this.endRelationship = endNode.getSingleRelationship( > SortedTree.RelTypes.KEY_VALUE, Direction.INCOMING ); > > So if the end node has more than one incoming KEY_VALUE relationship a more > than one relationship exception is thrown. > > Instead of the getSingleRelationship I was planning on iterating over the > relationships and matching the UUID stored at the root end of the IR with > one of the KEY_VALUE relationships (which is why using a unique id is > necessary rather than the relationship type). Note: there will actually > still be an issue if the same IR has multiple relationships to the same leaf > node - still thinking about that might need . > > Is storing the UUID as two longs much quicker than storing it as a string? > Curious about this since in my current model I have all the domain objects > with UUID's, and these are all stored as strings. If it was going to help > with either memory or performance then I would be keen to migrate this to > two longs. > > Cheers > Bryce > > On Thu, Sep 8, 2011 at 11:07 AM, Niels Hoogeveen > <[email protected]>wrote: > > > > > Great work Bryce, > > I do have a question though. > > What is the rationale for the restriction mentioned under "1)". Do you need > > this for the general case (to make IndexedRelationshipExpander work > > correctly), or do you need it for your own application to throw that > > exception? If the latter is the case, I think it would be important to tease > > out the general case and offer this new behaviour as an option. > > A unique key for the index is a good idea anyway and can be added to > > SortedTree. Generate a UUID and store it in two long properties. That way > > the two values will always be read in the first fetch of the underlying > > PropertyContainer. A getId method on the TreeNodes can then return a String > > representation of of the two long values. > > IndexRelationships are a relatively new development, so I think you are one > > of the first to actually try it out. Personally I have chosen to directly > > work with SortedTree, because I am working within the framework of a wrapper > > API, so I can integrate the functionality behind the regular > > createRelationshipTo and getRelationships methods. > > I don't think API changes will be an issue at the moment. > > Niels > > > Date: Thu, 8 Sep 2011 10:22:11 +1200 > > > From: [email protected] > > > To: [email protected] > > > Subject: [Neo4j] Issues with IndexedRelationship > > > > > > Hi, > > > > > > As I mentioned a while ago I am looking at using IndexedRelationship's > > > within my application. The major thing that was missing for me to be > > able > > > to do this was IndexedRelationshipExpander being able to provide all the > > > relationships from the leaf end of indexed relationships through the the > > > root end. So I have been working on getting that support in there. > > > > > > However in writing this I have discovered a number of other issues that I > > > have also fixed, and at least one I am still working on. Since I was > > right > > > into the extra support for expanding the relationships it is hard to > > break > > > out these fixes as a separate commit (which I think would be ideal), so > > it > > > will most likely all come in together hopefully later today (NZ time). > > > > > > Just letting everyone know in case someone else is doing development > > against > > > indexed relationships. > > > > > > Quick run down of the issues, note: N -- IR(X) --> {A,B} below means > > there > > > is a indexed relationship from N to A & B, of type X. > > > > > > 1) Exception thrown when more than one IR terminates at a given node, > > e.g.: > > > N1 -- IR(X) --> {A,B,C,D} > > > N2 -- IR(X) --> {A,X,Y,Z} > > > Will throw an exception when using the IndexedRelationshipExpander on > > either > > > N1, or N2. > > > > > > 2) Start / End nodes are transposed when the IR has an direction of > > > incoming, i.e. the IR is created against N but across a set of incoming > > > relationships: > > > N <-- IR(Y) -- {A,B,C} > > > Will return 3 relationships N --> A, N --> B, N --> C. > > > > > > I have written tests for each of these, as well as a couple of other > > tests. > > > > > > Still completing (1) and have a little question about this. In order to > > fix > > > this I may need to introduce a unique ID stored against the IR both at > > the > > > root and at the leaves. Currently the relationship type is used to name > > the > > > IR at both root and leaves, but in the case above that means you can't > > tell > > > from node A which KEY_VALUE relationship belongs to which IR tree without > > > traversing the tree. > > > > > > So the question is adding this ID would mean that anyone who is already > > > using this wont have the ID, and therefore without care will be data > > > incompatible with the updated code. This could be managed via a check > > for > > > the ID when accessing the tree and if it isn't there doing a walk over > > the > > > tree to populate all the places where it is required. > > > > > > In general in developing against this code where do we sit on data > > > compatibility and API compatibility? > > > > > > Cheers > > > Bryce > > > _______________________________________________ > > > Neo4j mailing list > > > [email protected] > > > https://lists.neo4j.org/mailman/listinfo/user > > > > _______________________________________________ > > Neo4j mailing list > > [email protected] > > https://lists.neo4j.org/mailman/listinfo/user > > > _______________________________________________ > Neo4j mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ Neo4j mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
