arangosh> db.names.ensureIndex({ type: "persistent", fields: [ "first" ] }); { "deduplicate" : true, "fields" : [ "first" ], "id" : "names/16051", "isNewlyCreated" : true, "sparse" : false, "type" : "persistent", "unique" : false, "code" : 201 } arangosh> db.names.save({ "first" : "Tim" }); { "_id" : "names/16054", "_key" : "16054", "_rev" : "_WcJRgYe--_" } arangosh> db.names.save({ "first" : "Tom" }); { "_id" : "names/16058", "_key" : "16058", "_rev" : "_WcJRgYi--_" } arangosh> db.names.save({ "first" : "John" }); { "_id" : "names/16061", "_key" : "16061", "_rev" : "_WcJRgYi--B" } arangosh> db.names.save({ "first" : "Tim" }); { "_id" : "names/16064", "_key" : "16064", "_rev" : "_WcJRgYi--D" } arangosh> db.names.save({ "first" : "Tom" }); { "_id" : "names/16067", "_key" : "16067", "_rev" : "_WcJRgYm--_" }