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

Insert and remove:

var documentsToMove = db.collectionA.find({});
documentsToMove.forEach(function(doc) {
    db.collectionB.insert(doc);
    db.collectionA.remove(doc);
});

note: this method might be quite slow for large collections or collections holding large documents.