CODEWITHSUNDEEP
foreachneo4jcypher
LearnerFreak
LearnerFreak

Reputation: 69

Neo4j Cypher Query Error while executing nested Foreach

I am trying to execute the following cypher query to create a relationship between all the nodes which are present in the collection nodelist.

    START n=node(*)
    MATCH(n)
    WHERE has(n.Gender)
    WITH n.Gender as Gender
    WITH collect(n) as nodelist 
    FOREACH (i in RANGE(0,length(nodelist-2))|
    FOREACH(si in [nodelist[i]|
    FOREACH(si2 in[nodelist[i+1] |
    CREATE UNIQUE (si-[:KNOWS]->si2))))

It gives me an error in the second FOREACH loop at nodelist[i] .

I tried putting nodelist(i) and it gives me an error saying `-' expected but '|' found

Any idea where I am going wrong?

Upvotes: 1

Views: 940

Answers (2)

Luanne
Luanne

Reputation: 19373

If you want to create a knows relation between all nodes in a collection:

 MATCH(n)
 WHERE has(n.Gender)
 WITH collect(n) as nodelist 
 FOREACH (x IN nodelist | 
     FOREACH (y IN filter(z IN  nodelist WHERE NOT (z=x)) | 
         MERGE (x)-[:knows]-(y)
     )
 )

Note the direction of your relations. Each node will be connected to each other node in nodelist once in a particular direction. If you want double relations i.e. a-[knows]->b as well as b-[:knows]->a you'll have to modify the query accordingly.

Upvotes: 2

Sumeet Sharma
Sumeet Sharma

Reputation: 2583

Your first FOREACH should be like below. Also I think line 4 is redundant in your query. In case you want to collect gender you can directly do collect(n.Gender) as Gender. Incase you do need to use that line you need to pass n in the first WITH too, otherwise it wont be reconginized at the second WITH clause. Also you dont need to start with START n=node(*)

Try below

MATCH(n)
WHERE has(n.Gender)
WITH collect(n) as nodelist,collect(n.Gender) as Gender 
FOREACH (i in RANGE(0,length(nodelist)-2)|
FOREACH(si in [nodelist[i]]|
FOREACH(si2 in [nodelist[i+1]] |
CREATE UNIQUE (si)-[:KNOWS]->(si2) )))

Upvotes: 1

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