arango> db.demo.getIndexes()
[
  { 
    "id" : "demo/0", 
    "type" : "primary",
    "fields" : [ "_id" ]
  }, 
  { 
    "id" : "demo/2290971", 
    "unique" : true, 
    "type" : "hash", 
    "fields" : [ "a" ] 
  }, 
  { 
    "id" : "demo/2946331",
    "unique" : false, 
    "type" : "hash", 
    "fields" : [ "b" ] 
  },
  { 
    "id" : "demo/3077403", 
    "unique" : false, 
    "type" : "skiplist", 
    "fields" : [ "c" ]
  }
]