Question 115349 in Mongodb Question posted in
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Mongodb – Copy a huge bunch of documents one collection to another in mongosh

I am trying to copy a million document in a collection to another colletion.

> db.source_collection.find().forEach(function(doc) { db.dest_collection.insertOne(doc)});

This works fine. but I wonder it might cause any trouble to operating Database if I loop a million documents.

Can I give a sleep while looping in mongh shell?
Is there any better solution for this?

Please advise me.

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2

Answers


  1. 0

    You can use bulkWrite() rather than insertOne , it will reduce your time significantly.

    var bulk = db.dest_collection.initializeUnorderedBulkOp();
var counter = 0;
db.source_collection.find().forEach(function(doc) {
  bulk.insert(doc);
  counter++;
  if (counter % 1000 == 0) {
    bulk.execute();
    bulk = db.dest_collection.initializeUnorderedBulkOp();
  }
});
if (counter % 1000 != 0) {
  bulk.execute();
}

    In this code For every 1000 documents, the code executes the bulk operation using the execute() method, and then re-initializes the bulk operation. Finally, after all documents are processed, the code executes the remaining bulk operation.

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  2. 0

    If you use the aggregation $out stage, you can copy the documents directly on the server and avoid the network round trip to the client.

    db.source_collection.aggregate([{$out:"destination_collection"}])
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