Retreiving nested json or a tree from ArangoDB

Question

ArangoDB is great for retrieving a graph of data. A tree is a kind of graph.
We want to store data of buildings in a database. The structure of a building can be thought of as a hierarchy of parts.
The data structure is very simple: assemblies containing other assemblies, unlimited levels deep. Assemblies are stored as documents, and linked by an edge collection contains .

The data that I need, can be fetched with

FOR v, e, path IN 1..3 OUTBOUND
'assemblies/14810426' contains
RETURN path

The data is there, however, I want to have a json like

{name: "Office Building", 
 assemblies: [{name: "Director's office",
   assemblies: [{name: "Chair"}, {name: "Desk"}]}, 
{name: "Toilet}]}

Is there a way to get this format straight from ArangoDB, or do I need to write code myself to convert the graph path to a tree?
I guess writing a Foxx service is an option, but I would like to avoid that.

There is a similar question, with answer , but that was for the previous version of ArangoDB. It requires a bit of foxx code. I was hoping to have a solution, straight from AQL.

Answer 1

You could make use of subquery to aggregate results and add it to your return result.

AQL Query like this

FOR doc IN assemblies 
FILTER doc._id=='assemblies/14810426'
LET conn_docs=(
  FOR v,e,path IN 1..3 
    OUTBOUND doc contains RETURN {'name':v.name}
) 
RETURN {'name':doc.name,'assemblies':conn_docs}

would do the task, which aggregates the connected assemblies to a query doc and place those in the return result

Answer 2

I know you want to avoid Foxx, but if interested I've answered this for someone else who wanted to have recursive nesting for menu trees.

Have a look at my answer for Arangodb AQL recursive graph traversal for more info.