All very good points! And i have learnt to never underestimate others experiences. However, I think that in some application garbage-collection might be useful, especially apps with very interconnected graphs.
A traverser would do the job, but what if there could be a hook in Neo that could be called whenever a connection/node is created/deleted. Ten we could at the end of the transaction check if a node has no more incoming connections and is not a root node. The node can be safely deleted, and this would cascade such that all unreachable nodes are deleted. Since a hook can be implemented outside of the neo core, this would then be an optional feature.... just a thought. -atle On Wed, 2009-11-11 at 12:43 -0500, Todd Stavish wrote: > Based on my experience with Object Databases, I can't recommend a > persistent garbage collector implementation (PGC). Just like all parts > of your object model don't need to be expressed in your graph, > persistence doesn't need garbage collectors. > > Based on what I've seen implemented by customers, GC's are meant for > dynamic memory allocation only. One consequence, we found, is that > the PGC often delays the application. To avoid this, you end up > avoiding or delaying the PGC for a long time, which means there is no > automatic GC, so ultimately the application is making a manual process > of a supposedly automatic operation. > > The delay also ends up bloating the database, ie the impact of not > deleting the nodes is that you end up using more storage space, when > you create new nodes you end up allocating more because the old ones > are still around. > > Not sure about Neo4j, but this also ended up fragmenting the database > files. So for us, we found that we were setting ourselves up for > bloat and fragmentation, and poor performance because you are going to > have access more data. It was also kind of fragile, because if you > make a mistake and not root something, you may end up having the PGC > accidentally delete something that you wanted. We had a tragically sad > experience were a customer was complaining about the PGC taking a long > time, the PGC was deleting more objects then they intended, good data > was lost (the performance was fine). > > Please take this as a data point on the decision, it's possible that > PGCs could be implemented in a way that don't experience these > problems, and end-users could be guided to avoid pitfalls, or PGCs > might work for a certain class of applications and not others. > > -Todd > > > > > > > > On Fri, Nov 6, 2009 at 12:47 PM, Johan Svensson <[email protected]> > wrote: > > I'll jump in on this one then. > > > > Node or relationship IDs will only be reused if they are deleted. > > There is no possibility that any IDs change without deleting. > > > > Regards, > > -Johan > > > > On Fri, Nov 6, 2009 at 3:11 PM, Andrea Puddu <[email protected]> wrote: > >> Hi Peter, > >> > >> I'm sorry if I jump in the discussion. I have a question about > >> "garbage collection". > >> Are node IDs reused only if some node is deleted? I mean, is there any > >> possibility that some IDs change without deleting any nodes? And what > >> about relationship IDs? > >> > >> Thank you in advance. > >> Andrea > >> > > _______________________________________________ > > Neo mailing list > > [email protected] > > https://lists.neo4j.org/mailman/listinfo/user > > > _______________________________________________ > Neo mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user _______________________________________________ Neo mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
