arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/16156", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/16159", "_key" : "16159", "_rev" : "16159" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/16163", "_key" : "16163", "_rev" : "16163" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/16166", "_key" : "16166", "_rev" : "16166" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]