Great work Nils! /peter
Sent from my phone. On Jul 4, 2011 11:39 PM, "Niels Hoogeveen" <[email protected]> wrote: > > Made some more changes to the SortedTree implementation. Previously SortedTree would throw an exception if a duplicate entry was being added. > I changed SortedTree to allow a key to point to more than one node, unless the SortedTree is created as a unique index, in which case an exception is raised when an attempt is made to add a node to an existing key entry. > A SortedTree once defined as unique can not be changed to a non-unique index or vice-versa. > SortedTrees now have a name, which is stored in the a property of the TREE_ROOT relationship and in the KEY_VALUE relationship (a new relationship that points from the SortedTree to the Node inserted in the SortedTree). The name of a SortedTree can not be changed. > SortedTrees now store the class of the Comparator, so a SortedTree, once created, can not be used with a different Comparator. > SortedTree is now an Iterable, making it possible to use it in a foreach-loop. > Since there are as of yet, no unit tests for SortedTree, I will create those first before pushing my changes to Git. Preliminary results so far are good. I integrated the changes in my own application and it seems to work fine. > Todo: > Decide on an API for indexed relationships. (Community input still welcome).Write unit tests.Make SortedTree thread safe (Community help still welcome). > Niels > >> From: [email protected] >> To: [email protected] >> Date: Mon, 4 Jul 2011 15:49:45 +0200 >> Subject: Re: [Neo4j] Indexed relationships >> >> >> I forgot to add another recurrent issue that can be solved with indexed relationships: guaranteed unicity constraints. >> > From: [email protected] >> > To: [email protected] >> > Date: Mon, 4 Jul 2011 01:55:08 +0200 >> > Subject: [Neo4j] Indexed relationships >> > >> > >> > In the thread [Neo4j] traversing densely populated nodes we discussed the problems arising when large numbers of relationships are added to the same node. >> > Over the weekend, I have worked on a solution for the dense-relationship-nodes using SortedTree in the neo-graph-collections component. After some minor tweaks to the implementation of SortedTree, I have managed to get a workable solution, where two nodes are not directly linked by a relationship, but by means of a BTree (entirely stored in the graph). >> > Before continuing this work, I'd like to have a discussion about features, since what we have now is not just a solution for the dense populated node issue, but is actually a full fledges indexed relationship, which makes it suitable for other purposes too. >> > An indexed relationship can for example be used to maintain a sorted set of relationships in the graph, that is not necessarily huge, but large enough to make sorting on internal memory too expensive an operation, or situations where only one out of a large number of relationships is actually traversed in most cases. >> > There are probably more use cases for in-graph indexed relationships, so I'd like to know what features are desirable and what API would Neo4J users appreciate. >> > P.S. I still think it would be good to consider, if technically possible, partitioning the relationship store per relationship type and per direction. The indexed relationship solution works, but is of course slower than a direct relationship, both with respect to insert time and traversal time. If dense relationships are never traversed going out of the dense node, the extra structure maintained by the BTree is only extra burden. >> > P.P.S. If there are people with experience to make an implementation thread safe, please volunteer to help make the implementation production proof. >> > Niels >> > _______________________________________________ >> > 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
