从AQL遍历返回单个顶点和边的文档

Question

When I do a traversal in Arango I get an array of json structures that look like this:

{
  "vertex" : {
    "_id" : "vertices/857831247835",
    "_key" : "857831247835",
    "_rev" : "857831247835",
  },
  "path" : {
    "edges" : [
      {
      "_id" : "edges/857831575515",
      "_key" : "857831575515",
      "_rev" : "857831575515",
      "_from" : "vertices/857831247835",
      "_to" : "vertices/857821417435",
    }
    ],
    "vertices" : [
      {
      "_id" : "vertices/857821417435",
      "_key" : "857821417435",
      "_rev" : "857821417435",
    },
    {
      "_id" : "vertices/857831247835",
      "_key" : "857831247835",
      "_rev" : "857831247835",
    }
    ]
  },
  "startVertex" : "vertices/857821417435"
}

Is there a way of getting all edges/vertices found in the traversal into a single structure like the one above using AQL?

Answer 1

You can actually use two ways to get your result:

Easy-way extend your AQL-query:

FOR x IN (<<Your previous query here>>) RETURN {edges: x.path.edges, vertices: x.path.vertices, vertex: x.vertex, startVertex: x.startVertex}

More performant way (you short-circuit the object creation): Register a user-defined function following: https://docs.arangodb.com/AqlExtending/Functions.html One time using arangosh .

This should be something like this:

require("org/arangodb/aql/functions").register("myVisitors::flatVisitor", function (config, result, vertex, path) { result.push({ vertex: vertex, edges: path.edges, vertices: path.vertices}); });

And then in your AQL add the additional option visitor: "myVisitors::flatVisitor" same as paths: true .

BTW: paths: true will be ignored in this case as it was used in our default visitor only.

HINT: If you only need certain attributes in your result instead of the complete document only return these ones in your visitor. This will give a significant performance improvement.

Answer 2

A bit old but for the sake of new visitors to this question. another way is to accumulate edges from the path uniquely (syntax is of the arangojs official client):

graph.traversal('verticies/startkey', {
    direction: 'any',
    init: `result.verticies = [];
    result.edges = [];`,
    visitor: `
        path.edges
            .forEach(function (x) {
                if (result.edges.indexOf(x) === -1) {
                    result.edges.push(x);
                }
            });
        result.verticies.push(vertex);
    `,
    uniqueness: {
        "vertices": "global",
        "edges": "global"
    }
});