Hi,
You can do nested ifThenElses. One way to think about things is not as "big ol'
one-liners."
g.V.ifThenElse{ ifStatement } {
thenStatement
} {
elseStatement
}
With new lines, the embeddness then starts to look like plain ol' C-style
syntax.
Also note that in Gremlin 1.4 (releasing this week), the _() will not be needed
anymore for start objects. I learned how to solve that at SpringONE :).
Thanks,
Marko.
http://markorodriguez.com
On Dec 5, 2011, at 8:27 PM, Romiko Derbynew wrote:
> Marko,
>
> I am thinking of using this statement.
> g.V.ifThenElse{it.out('hasCentre').filter{it == aCentre}.hasNext()}{}{println
> "${it} has center unknown"}
>
> to get nodes that DO NOT have a relationship, is this the best way to do it?
> I guess so, if this is the case, I am now adding support to the .NET graph
> client to support ifThenElse expressions. I am wondering though, as I am
> designing the interface for it, can and ifThenElse have nested ifThenElse
> expressions as well? I guess "it" and _() can be used within them?
>
> Cheers
>
> -----Original Message-----
> From: user-boun...@lists.neo4j.org [mailto:user-boun...@lists.neo4j.org] On
> Behalf Of Marko Rodriguez
> Sent: Saturday, 3 December 2011 4:10 AM
> To: Neo4j user discussions
> Subject: Re: [Neo4j] Gremlin Query - Help
>
> Hi,
>
>> Scenario 1:
>> I would like to get all Nodes that do not have a relationship to another
>> node. What is the best way to do this Gremlin?
>>
>> Root => NodeA => NodeB
>> Root => NodeC
>>
>> Output should be NodeC
>
> I don't understand the problem.
>
>> Scenario 2:
>> Root = > User -> Centre
>>
>> I would like to get all centres for userA, and then get all users who
>> are also linked to the same centres of the userA
>
> userA.out('hasCentre').in('hasCentre').except([userA])
>
>> Scenario 3:
>> User => Centre
>> I would like to get all users that do not have a link to a Centre, and if
>> this is the case, do a projection that returns a fake centre with property
>> "Unknown"
>
> g.V.ifThenElse{it.out('hasCentre').filter{it ==
> aCentre}.hasNext()}{}{println "${it} has center unknown"}
>
> If you have an index of your Users, then its more efficient to hit that
> index, then iterate through all vertices (g.V). E.g.
>
> g.idx(T.v)[[type:'User']].ifThenElse....
>
>> Scenario 4:
>>
>> REFERRAL => PERSON
>>
>> I would like to combine a query that gets all Referrals that are
>> linked to a person and project a table result (contains referrals and
>> person property values (this is easy to do) However, I then want to do a
>> SPLIT query, that gets referrals without the persons, and then MERGE both
>> back into the table projection? So table projecton might look like this.
>> I guess this is done with .table().it{}....cap, but what I am not sure, is
>> how to do a split and merge in parallel and then get that merge projected
>> into the same table.
>
>
> I don't quite understand your problem, but here is an example of splitting
> and merging.
>
> g.v(1).out('knows').copySplit(_().out('knows').name,
> _().out('created').name).fairMerge
>
> This will get all the people that v[1] knows and then generate two parallel
> pipeline. Each friend of v[1] is copied to each of the 2 parallel pipelines.
> One pipeline will get their friend's names and one will get their created
> project's names. It will then merge those two parallel pipelines into a
> single stream. You can do either fairMerge or exhaustMerge depending on the
> merging algorithm you want. fairMerge is more memory efficient. I need to
> write more about split/merge in the Gremlin documentation.
>
> https://github.com/tinkerpop/gremlin/wiki/Split-Merge-Pattern <-- will
> work on it :)
>
> HTH,
> Marko.
>
> http://markorodriguez.com
>
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