mongodb move documents from one collection to another collection

Question

How can documents be moved from one collection to another collection in MongoDB?? For example: I have lot of documents in

Answer 1

It can be done on the server-side using the $merge operator (starting from MongoDB 4.2).

db.getCollection("sourceColl").aggregate([
  { $merge: {
     into: "targetColl",
     on: "_id",
     whenMatched: "fail",
     whenNotMatched: "insert"
  }}
]);
db.getCollection("sourceColl").deleteMany({})