[Neo4j] Lucene Index on Relationships
Paul A. Jackson
Paul.Jackson at pb.com
Mon Jun 21 14:44:14 CEST 2010
I am not sure was a per-node relationship index is. I concur that a relationship index doesn't help if each node has a relationship of the type we are interested in (like in a graph of employees, each employee would have a Manager relation). However, in a graph where there are lots of nodes and only a few of them have a relationship of the type we are interested in, it seems logical to me that the optimal way to start a query is with the index into the relationships.
From: user-bounces at lists.neo4j.org [mailto:user-bounces at lists.neo4j.org] On Behalf Of Mattias Persson
Sent: Monday, June 21, 2010 8:36 AM
To: Neo4j user discussions
Subject: Re: [Neo4j] Lucene Index on Relationships
how do you guys expect indexing for relationships to work? Would it be
an index just as for nodes... or per node? I often hear that it'd
speed up traversals if a node has many, many neighbours. But if the
relationship index would be for the entire graph (not per node) that
wouldn't really help, would it?
2010/6/21 Craig Taverner <craig at amanzi.com>:
> A side comment, since I think indexing relationships with lucene might be
> good, but think there might be alternatives for your current example.
> You said that the relationship property is a float from 0 to 1, so you
> cannot use relationship types, but actually, when you consider that any
> index is usually created by breaking data ranges (continuous or discrete)
> into fewer, more discrete ranges, you can use a relationship type to
> represent a range of floats. For example, if you have roughly even
> distribution of floats between 0 and 1, try divide that into 100 parts
> (0%-100%, or 0.01 to 1.00), and make a relationship type for each. This
> would certainly facilitate traversing relationships of specific float values
> (at least improve the performance dramatically, as in an index).
> Of course, this example focuses on traversing from a particular document. If
> you are searching for all relationships in the entire database with
> particular float values, then a separate index would be better.
> On Mon, Jun 21, 2010 at 2:11 PM, Marius Kubatz <marius.kubatz at udo.edu>wrote:
>> Hello guys, hello community!
>> I'm currently evaluating neo4j for my thesis and have a wish :)
>> I have already opened a ticket for this,(
>> https://trac.neo4j.org/ticket/241 ) but
>> I would like to hear what you guys think about it.
>> Basically it just involves the ability to index Neo4j Relationships with
>> Lucene Index.
>> Neo4j works great on sparse graphs, but what happens when you have a very
>> tight graph with several thousands of neighbors to one node?
>> Additionally as soon as you store informations on Relationships you will
>> into trouble, because you will have to iterate through all those edges to
>> find the
>> properties you seek.
>> If this sounds far fetched please take a look at this example where one
>> might need properties on Relationships:
>> One "Document" node is related to another Document node by a similarity
>> function which is stored in the Relationships between those document nodes.
>> Lets just say that we save a float between [0 - 1] on those relationships,
>> which makes it impossible to create RelationshipTypes for every value.
>> Using Index to fetch Relationships by their indexed properties would
>> speed up the process and increase the attractiveness of using properties on
>> Relationships. I would love to have quick access to Relationship properties
>> where I could add and implement fuzzy
>> logic, probabilities, Bayesian networks, similarities, ranking ... and so
>> ... As said thank you for Relationship properties, they are great and
>> already there, but what I miss is quick access to them.
>> Thank you very much and best regards!
>> "Programs must be written for people to read, and only incidentally for
>> machines to execute."
>> - Abelson & Sussman, SICP, preface to the first edition
>> Neo4j mailing list
>> User at lists.neo4j.org
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Mattias Persson, [mattias at neotechnology.com]
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