[{name:"playlist name",urls:["url1","url2","url3"]}]

db.collection.update({},[{$set:{urls:{$concatArrays:[{$slice:["$urls",1/**Put Index 0,1,2...*/]},{$slice:["$urls",{$add:[1,1/**Put Index 0,1,2...*/]},{$size:"$urls"}]}]}}}])