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 collection A and I want to move all 1 month older documents to collection B (these 1 month older documents should not be in collection A).

Using aggregation we can do copy. But what I am trying to do is moving of documents. What method can be used to move documents?

Answer 1

The bulk operations @markus-w-mahlberg showed (and @mark-mullin refined) are efficient but unsafe as written. If the bulkInsert fails, the bulkRemove will still continue. To make sure you don't lose any records when moving, use this instead:

function insertBatch(collection, documents) {    var bulkInsert = collection.initializeUnorderedBulkOp();    var insertedIds = [];    var id;    documents.forEach(function(doc) {      id = doc._id;      // Insert without raising an error for duplicates      bulkInsert.find({_id: id}).upsert().replaceOne(doc);      insertedIds.push(id);    });    bulkInsert.execute();    return insertedIds;  }    function deleteBatch(collection, documents) {    var bulkRemove = collection.initializeUnorderedBulkOp();    documents.forEach(function(doc) {      bulkRemove.find({_id: doc._id}).removeOne();    });    bulkRemove.execute();  }    function moveDocuments(sourceCollection, targetCollection, filter, batchSize) {    print("Moving " + sourceCollection.find(filter).count() + " documents from " + sourceCollection + " to " + targetCollection);    var count;    while ((count = sourceCollection.find(filter).count()) > 0) {      print(count + " documents remaining");      sourceDocs = sourceCollection.find(filter).limit(batchSize);      idsOfCopiedDocs = insertBatch(targetCollection, sourceDocs);        targetDocs = targetCollection.find({_id: {$in: idsOfCopiedDocs}});      deleteBatch(sourceCollection, targetDocs);    }    print("Done!")  }