Cypher - loading results while optionally adding count of relationships

Question

I'm using a graph database to establish a relationship between folders, their children and users (be it owners or sharers of the folder).

Here is an example of my structure. Where orange are folders and blue are users. -

What I want my query to achieve: It should return direct children of the folder under query, and while doing so determine if the child folder being returned is being shared.

My query

MATCH (:Folder { name: 'Nick Hamill' })-[:CHILD]->(children:Folder)

WITH children

OPTIONAL MATCH path = (children)<-[*]-(:User)

UNWIND RELATIONSHIPS(path) AS r WITH children, r

WHERE TYPE(r) = 'SHARES'

RETURN children AS model, COUNT(r) > 0 AS shared

So the query works brilliantly (perhaps a little optimisation needed?) when there is a related user (see below), however, the query fails to return any result if there is no user relationship. I personally can't see why this is because it's an optional match, and surely the count could just return empty?

╒══════════════════════════════════════════════════════════════════════╤════════╕
│"model"                                                               │"shared"│
╞══════════════════════════════════════════════════════════════════════╪════════╡
│{"name":"Dr. Denis Abshire","created_at":"2019-10-11 13:54:58","id":"c│true    │
│f5e084f-d963-35d3-9c6f-fe29b86f6d43","updated_at":"2019-10-11 13:54:58│        │
│"}                                                                    │        │
└──────────────────────────────────────────────────────────────────────┴────────┘

The query should be relatively self-explanatory but for the sake of clarity here's some expected outputs -

| Query Folder         | Returned Folder  | Shared? |
|----------------------|------------------|---------|
| Miss Dessie Oritz II | Nick Hamill      | TRUE    |
| Nick Hamill          | Dr Denis Abshire | TRUE    |
| Samara Russell       | Shemar Huels PhD | FALSE   |
| Shemar Huels PhD     | Hazle Ward       | FALSE   |

I'm running neo4j 3.5.11 community edition. I feel like this should be a fairly easy solution, I'm just meeting the limits of my extremely limited cypher knowledge.

Appreciate any help!

You should tell us which version of the language you are using and provide some examples of expected results on the provided database — Sterconium
@Sterconium - thanks, I've added an example result and version — Chris
I saw it, but what about the other folders? What should it return with, say, "Samara Russel" ? — Sterconium

logisima logisima · Accepted Answer · 2019-10-11T14:19:20

I don't undertsand why you are using this in your query :

OPTIONAL MATCH path = (children)<-[*]-(:User)
UNWIND RELATIONSHIPS(path) AS r WITH children, r
WHERE TYPE(r) = 'SHARES'

With (children)<-[*]-(:User) you are searching all the path (without restriction on its size) between the children & User nodes. And with the WHERE TYPE(r) = 'SHARES' you only want the SHARES relationship ...

So your query will work on this kind of pattern : (children)<-[:CHILD]-(:Folder)<-[:CHILD]-(:Folder)<-[:SHARES]-(:User)

Is it what you want ?

If so, can you try this query :

MATCH (:Folder { name: 'Nick Hamill' })-[:CHILD]->(children:Folder)
RETURN children AS model, size((children)<-[:CHILD*0..]-(:Folder)<-[:SHARES]-(:User)) > 0 AS shared

Cypher - loading results while optionally adding count of relationships

1 Answers