Cypher q: function to get start/end nodes of relationships?

[Aseem Kishore]

Just like you can dynamically WHERE on the type of a relationship, I thought there was a way to dynamically WHERE on the direction as well -- by comparing the start and end nodes of a relationship.

But neither START(rel) / END(rel) nor rel.start / rel.end work for me, and neither on 1.6 nor on 1.8/9 (whatever's on console.neo4j.org). And looking through the docs, I can't find any mention of these functions.

Is this not implemented yet and my memory was only of a discussion / feature request? Or is it some other name? Thanks!

Aseem

[Wes Freeman]

There is a feature request for that, I think:

https://github.com/neo4j/community/issues/693

Aseem

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[Michael Hunger]

There is a feature request for that: https://github.com/neo4j/community/issues/693

Also treating relationships as a short path would be a nice thing.

so one can do nodes(r). or head(nodes(r)) tail(nodes(r)).

Michael

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[Aseem Kishore]

Ah cool, thanks guys.

It occurred to me that in the meantime, you could use a pattern WHERE:

MATCH (a) -[r:FOLLOWS]- (b)

WHERE (a) -[r]-> (b)

Cool, at least that's possible. Were pattern WHEREs added in 1.7?

Aseem

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[Andres Taylor]

On Sat, Oct 13, 2012 at 4:59 PM, Aseem Kishore <aseem....@gmail.com> wrote:

Ah cool, thanks guys.

It occurred to me that in the meantime, you could use a pattern WHERE:

MATCH (a) -[r:FOLLOWS]- (b)

WHERE (a) -[r]-> (b)

Hehe... Didn't realise that. Cool! :)

 

Cool, at least that's possible. Were pattern WHEREs added in 1.7?

 No, they made it in in 1.8.

Andrés

[Aseem Kishore]

Thanks Andrés!

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[Michael Hunger]

actually you can even use 

MATCH p = (a) -[r:FOLLOWS]- (b)

WHERE a = head(nodes(p))

Michael

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[Andres Taylor]

On Sat, Oct 13, 2012 at 5:43 PM, Michael Hunger <michael...@neotechnology.com> wrote:

actually you can even use 

MATCH p = (a) -[r:FOLLOWS]- (b)

WHERE a = head(nodes(p))

Sorry amigo, but that doesn't work. The path always follows the pattern you have described - in this pattern, a will _always_ be a the head of p.  

Andrés

[Michael Hunger]

Sure I know :)

Was just demonstrating a "true" case

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[Aseem Kishore]

Ah, in my case at least, I'm interested in both directions -- hence not specifying a direction in MATCH. I'm having trouble imagining a case where you *wouldn't* be interested in both directions if you wanted to WHERE on the direction.

(In my case, my WHERE looks something like (direction in AND foo) OR (direction out AND bar).)

Aseem

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[Wes Freeman]

Another use case for this is something like this, match both directions where one direction or foo:

http://stackoverflow.com/questions/12814038/neo4j-cypher-query-filter-specific-relation/12815197#12815197

Wes

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[Peter Neubauer]

Agreed Wes,
Looks like a very useful addition.

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Cheers,

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