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From Dmitry Unkovsky <oil.cray...@gmail.com>
Subject Re: Map-reduce graph traversal in CouchDB?
Date Sat, 04 Jul 2009 13:36:58 GMT
For all I can imagine you can have view, say, 'edges', with key [type,start,end]
To traverse graph for query 'friends-of-friends' you do multiple
queries to view's _bulk_doc with
(at first)
include_docs=false (that is default) and
start_key=[<type-of-edge>,<current-node-id>,'aaaaaaaaa'] and
end_key=[<type-of-edge>,<current-node-id>,'ZZZZZZZZZZ']
then, having all neighbor nodes on output from this query, you iterate
over their neighbours, having each node's neighbours in alike query at
each turn.

That will probably work good for not too intensive and deep
traversals, but you may get too many queries for deep and frequent
"graph queries".
For what I have read from neo4j papers, they have tight compressed
edges structure with memory mapped io on it, so if IO to edges don't
have a very 'long tail', i.e. many edges are accessed frequently, and
you have fair big ratio of ram/pending io on edges, neo4j will give
you stronger platform for deep traversal.

These are rather diffuse reasonings,
But you can get the real answer suitable to you if you do benchmark on
your estimated avarage use-case.

2009/7/3 David Beckwith <thirdreplicator@gmail.com>:
> Hi,
>
> I'm deciding between CouchDB and Neo4j for a project.  What's really
> important to me is the speed of graph traversal and scalability.
>
> CouchDB wins in scalability I think, but probably Neo4j wins in graph
> traversal.
>
> http://highscalability.com/neo4j-graph-database-kicks-buttox
>
> How well does CouchDB with graph traversal.  And is there a way to map-
> reduce graph traversal?
>
> Thanks,
> David :)
>

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