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

From MongoDB 3.0 up, you can use the copyTo command with the following syntax:

db.source_collection.copyTo("target_collection")

Then you can use the drop command to remove the old collection:

db.source_collection.drop()

Answer 2

First option (Using mongo dump)

1.Get a dump from collection

mongodump -d db -c source_collection

2.Restore from collection

mongorestore -d db -c target_collection dir=dump/db_name/source_collection.bson

Second Option

Running aggregate

db.getCollection('source_collection').aggregate([ { $match: {"emailAddress" : "apitester@mailinator.com"} }, { $out: "target_collection" } ])

Third Option (Slowest)

Running a through for loop

db.getCollection('source_collection').find().forEach(function(docs){ db.getCollection('target_collection').insert(docs); }) print("Rolleback Completed!");

Answer 3

Update 2

Please do NOT upvote this answer any more. As written @jasongarber's answer is better in any aspect.

Update

This answer by @jasongarber is a safer approach and should be used instead of mine.

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Provided I got you right and you want to move all documents older than 1 month, and you use mongoDB 2.6, there is no reason not to use bulk operations, which are the most efficient way of doing multiple operations I am aware of:

> var bulkInsert = db.target.initializeUnorderedBulkOp()
> var bulkRemove = db.source.initializeUnorderedBulkOp()
> var date = new Date()
> date.setMonth(date.getMonth() -1)
> db.source.find({"yourDateField":{$lt: date}}).forEach(
    function(doc){
      bulkInsert.insert(doc);
      bulkRemove.find({_id:doc._id}).removeOne();
    }
  )
> bulkInsert.execute()
> bulkRemove.execute()

This should be pretty fast and it has the advantage that in case something goes wrong during the bulk insert, the original data still exists.

---

Edit

In order to prevent too much memory to be utilized, you can execute the bulk operation on every x docs processed:

> var bulkInsert = db.target.initializeUnorderedBulkOp()
> var bulkRemove = db.source.initializeUnorderedBulkOp()
> var x = 10000
> var counter = 0
> var date = new Date()
> date.setMonth(date.getMonth() -1)
> db.source.find({"yourDateField":{$lt: date}}).forEach(
    function(doc){
      bulkInsert.insert(doc);
      bulkRemove.find({_id:doc._id}).removeOne();
      counter ++
      if( counter % x == 0){
        bulkInsert.execute()
        bulkRemove.execute()
        bulkInsert = db.target.initializeUnorderedBulkOp()
        bulkRemove = db.source.initializeUnorderedBulkOp()
      }
    }
  )
> bulkInsert.execute()
> bulkRemove.execute()