[{"_id":ObjectId("605c666a15d2612ed0afedd2"),"name":"Anna","data":[{"code":"a","qty":3},{"code":"b","qty":4}]},{"_id":ObjectId("605c666a15d2612ed0afedd3"),"name":"James","data":[{"code":"c","qty":5},{"code":"d","qty":6}]}]

db.collection.update({},[{$set:{data:{$reduce:{input:"$data",initialValue:[],in:{$concatArrays:["$$value",[{$cond:[{$eq:[{$size:"$$value"},0]},{$mergeObjects:["$$this",{code:"$name"}]},"$$this"]}]]}}}}}],{multi:true})