[Neo4J 2.1.2] / Cypher / Returning array property associated to an aggregate in one shot

[Michael Azerhad]

Hi,

Let's suppose this Cypher query snippet: 

RETURN user.name, count(game.name)

=> a user can have multiple video games

No matter the example is, the important thing is that I can count names of user's video games associated with the user's name. 

Result would be:

            NAME                    NUMBER_OF_GAMES
            Michael                       18

Now, suppose that the user.name is replaced by an array property: let's imagine user.ranks       

I expect the output to be:

           RANKS                  NUMBER_OF_GAMES
          [1,2,3]                      18  

However the result is a cartesian product over the array:

          RANKS                  NUMBER_OF_GAMES
              1                     ... //no matter the number of games is
              2                     ...
              3                     ...

          

Why isn't it possible to return the array in one shot ?

Thanks,

Michael 

[Michael Azerhad]

I managed to do the trick with: 

RETURN extract(d IN user.ranks | d) as ranks, count(game.name) 

=> one shot :)

Michael

[Michael Hunger]

Something is wrong there.

An array property is never converted into individual rows by cypher you must have done something differently.

Can you please share the full query?

Just tried it, works perfectly fine.

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[Michael Azerhad]

Hi Michael :)

So here's the initial full query (with the non-expected output, no "one shot").

The context is:  I want to retrieve the number of participants corresponding to meetings that the user 123 made (meaning participated too), associated to a meeting's array properties.

MATCH (meeting:Meeting)<-[:TO]-(part)-[:PARTICIPATES]->(user:User {id: "123"})   //traverse user123's participations
MATCH (meeting)<-[:TO]-(participation)-[:PARTICIPATES]->(participant)  //traverse to retrieve all the participants for the meetings matched
RETURN meeting.myArrayProperties AS myArrayProperties, count(participant) AS total_participants

Didn't display the whole array in one column. 

However, if I replace the array properties with a standard field like, meeting.title, it works.

So, arrays are weird.. IMHO ;)

Here's what I did to fix it:

MATCH (meeting:Meeting)<-[:TO]-(part)-[:PARTICIPATES]->(user:User {id: "123"})
MATCH (meeting)<-[:TO]-(participation)-[:PARTICIPATES]->(participant)
RETURN extract(property IN meeting.myArrayProperties | property) AS myArrayProperties, count(participant) AS total_participants

Thanks for your feedback, I appreciate.

Michael

[Michael Azerhad]

Hi Michael,

What better than a GraphGist to show you the issue :) 

http://gist.neo4j.org/?fc9672035185189521cf

So I would expect the output: 

MyMeetingTitle

[1, 2, 3]

2

rather than:

MyMeetingTitle	[1, 2, 3]	1
MyMeetingTitle	[1, 2, 3]	1

Do you see an obvious reason ?

Many thanks, 

Michael

 

[Michael Azerhad]

I've just updated the graphgist: http://gist.neo4j.org/?fc9672035185189521cf  in order to better explain my issue.

In case where someone already opened it..

[Michael Hunger]

Hi Michael,

thanks again for pointing it out. It was a Cypher Bug which is fixed in the next release.

A workaround is to convert the array into a collection as you already showed.

Cheers,

Michael

[michael azerhad]

Hi Michael,

Good to know :) 

Thanks a lot for warning me!

Michael 

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