How to display relationships ids in the apoc.convert.toTree json result?

Question

I'm using the apoc.convert.toTree procedure for my neo4j database. I would like to get the ids of the relationships like the nodes but I can't find how.

In the exemple, we can see that the id of the node is displayed :

{
         "_type":"Movie",
         "_id":33,
         "title":"Something's Gotta Give",
         "acted_in.roles":[
            "Julian Mercer"
         ]
}

But I would like to have also the id of the relationship :

{
         "_type":"Movie",
         "_id":33,
         "title":"Something's Gotta Give",
         "acted_in.roles":[
            "Julian Mercer"
         ]
         "acted_in._id": 65
}

I've tried to use the map config to get them :

CALL apoc.convert.toTree(paths, true, {
  rels:  {acted_in: ['_id']}
})

Unfortunately, It doesn't work. Do you have any suggestions ?

Answer 1

Unfortunately, that APOC function does not return the _id value of the relationship :ACTED_IN. Notice that the variable is a class variable which is preceded by _, so it implicitly added in the result.

Try to experiment on the APOC and put a property in the relationship that doesn't exists like 'roleX':

CALL apoc.convert.toTree(paths, true, {
  rels:  {acted_in: ['roleX']}
})

The result is none of the relationship properties (like roles), will be shown. It is because it cannot find a match on the list of properties in the relationship :ACTED_IN. The property _id is not an explicit property on :ACTED_IN so it does not work.

I would suggest a hack so it is up to you if you like it. 1) create another property named: id which is the same value with id(rel) 2) then do your query such as {acted_in: ['id']}.

Sample below:

MATCH ()-[r:ACTED_IN]->() 
SET r.id = id(r)

then:

CALL apoc.convert.toTree(paths, true, {
  rels:  {acted_in: ['id']}
})

Result:

{
  "born": 1964,
  "_type": "Person",
  "name": "Keanu Reeves",
  "acted_in": [
    {
      "_type": "Movie",
      "_id": 154,
      "acted_in.id": 221,
      "title": "Something's Gotta Give",
      "released": 2003
    }
  ],
  "_id": 1
}