Vertex Centric Indexes for sorting

Question

Let's say I have supernodes with many edges and would like to quickly return top N edges for a given node. How can I do it with ArangoDB Vertex Centric Index https://docs.arangodb.com/3.11/index-and-search/indexing/working-with-indexes/vertex-centric-indexes/?

I can create skiplist Vertex Centric Index

arangosh> db.collection.ensureIndex({ type: "skiplist", fields: [ "_from", "points" ] })

but the optimiser does not pick it up with sort query

FOR edge IN collection
  FILTER edge._from == "vertices/123456" 
  SORT edge.points DESC
  LIMIT 0, 10
  RETURN edge

It also seems that arango optimizer does not pick up skiplist Vertex Centric Index in traversal syntax however documentation says it should:

FOR v, e, p IN 3..5 OUTBOUND @start GRAPH @graphName
  FILTER p.edges[*].points ALL >0
  RETURN v

Answer 1

quickly return top N edges for a given node

It would be better to start with the node:

FOR v, e IN 1..1 ANY @start @edges
  SORT e.points DESC
  LIMIT 10
  RETURN e

This should be about as good as you can get with the current version (3.3) of ArangoDB, assuming you let ArangoDB index _from -- I doubt that adding a skiplist for .points is going to make any (beneficial) difference, unless perhaps you use it in a FILTER.

(I believe that indexing _from using a skiplist would be unwise here. If edges is an Edges collection, it will already be properly indexed.)