How to copy a collection from one database to another in MongoDB

The best way is to do a mongodump then mongorestore. You can select the collection via:

mongodump -d some_database -c some_collection

[Optionally, zip the dump (zip some_database.zip some_database/* -r) and scp it elsewhere]

Then restore it:

mongorestore -d some_other_db -c some_or_other_collection dump/some_collection.bson

Existing data in some_or_other_collection will be preserved. That way you can "append" a collection from one database to another.

Prior to version 2.4.3, you will also need to add back your indexes after you copy over your data. Starting with 2.4.3, this process is automatic, and you can disable it with --noIndexRestore.

Actually, there is a command to move a collection from one database to another. It's just not called "move" or "copy".

To copy a collection, you can clone it on the same database, then move the cloned collection.

To clone:

> use db1
switched to db db1

> db.source_collection.find().forEach(
      function(x){
          db.collection_copy.insert(x)
      }
  );

To move:

> use admin
switched to db admin

> db.runCommand(
      {
          renameCollection: 'db1.source_collection',
          to              : 'db2.target_collection'
      }
  );

The other answers are better for copying the collection, but this is especially useful if you're looking to move it.

I would abuse the connect function in mongo cli mongo doc. so that means you can start one or more connection. if you want to copy customer collection from test to test2 in same server. first you start mongo shell

use test
var db2 = connect('localhost:27017/test2')

do a normal find and copy the first 20 record to test2.

db.customer.find().limit(20).forEach(function(p) { db2.customer.insert(p); });

or filter by some criteria

db.customer.find({"active": 1}).forEach(function(p) { db2.customer.insert(p); });

just change the localhost to IP or hostname to connect to remote server. I use this to copy test data to a test database for testing.

If between two remote mongod instances, use

{ cloneCollection: "<collection>", from: "<hostname>", query: { <query> }, copyIndexes: <true|false> } 

See http://docs.mongodb.org/manual/reference/command/cloneCollection/

I'd usually do:

use sourcedatabase;
var docs=db.sourcetable.find();
use targetdatabase;
docs.forEach(function(doc) { db.targettable.insert(doc); });

for huge size collections, you can use Bulk.insert()

var bulk = db.getSiblingDB(dbName)[targetCollectionName].initializeUnorderedBulkOp();
db.getCollection(sourceCollectionName).find().forEach(function (d) {
    bulk.insert(d);
});
bulk.execute();

This will save a lot of time. In my case, I'm copying collection with 1219 documents: iter vs Bulk (67 secs vs 3 secs)

Unbelievable how many up-votes are given for agonizingly slow one-by-one copy of data.

As given in other answers the fastest solution should be mongodump / mongorestore. There is no need to save the dump to your local disk, you can pipe the dump directly into mongorestore:

mongodump --db=some_database --collection=some_collection --archive=- | mongorestore --nsFrom="some_database.some_collection" --nsTo="some_or_other_database.some_or_other_collection" --archive=-

In case you run a sharded cluster, the new collection is not sharded by default. All data is written initially to your primary shard. This may cause problems with disk space and put additional load to your cluster for balancing. Better pre-split your collection like this before you import the data:

sh.shardCollection("same_or_other_database.same_or_other_collection", { <shard_key>: 1 });
db.getSiblingDB("config").getCollection("chunks").aggregate([
   { $match: { ns: "some_database.some_collection"} },
   { $sort: { min: 1 } },
   { $skip: 1 }
], { allowDiskUse: true }).forEach(function (chunk) {
   sh.splitAt("same_or_other_database.same_or_other_collection", chunk.min)
})

You can use aggregation framework to resolve your issue

db.oldCollection.aggregate([{$out : "newCollection"}])

It should be noted, that indexes from oldCollection will not copied in newCollection.

There are different ways to do the collection copy. Note the copy can happen in the same database, different database, sharded database or mongod instances. Some of the tools can be efficient for large sized collection copying.

Aggregation with $merge: Writes the results of the aggregation pipeline to a specified collection. Note that the copy can happen across databases, even the sharded collections. Creates a new one or replaces an existing collection. New in version 4.2. Example: db.test.aggregate([ { $merge: { db: "newdb", coll: "newcoll" }} ])

Aggregation with $out: Writes the results of the aggregation pipeline to a specified collection. Note that the copy can happen within the same database only. Creates a new one or replaces an existing collection. Example: db.test.aggregate([ { $out: "newcoll" } ])

mongoexport and mongoimport: These are command-line tools. mongoexport produces a JSON or CSV export of collection data. The output from the export is used as the source for the destination collection using the mongoimport.

mongodump and mongorestore: These are command-line tools. mongodump utility is for creating a binary export of the contents of a database or a collection. The mongorestore program loads data from a binary database dump created by mongodump into the destination.

db.cloneCollection(): Copies a collection from a remote mongod instance to the current mongod instance. Deprecated since version 4.2.

db.collection.copyTo(): Copies all documents from collection into new a Collection (within the same database). Deprecated since version 3.0. Starting in version 4.2, MongoDB this command is not valid.

NOTE: Unless said the above commands run from mongo shell.

Reference: The MongoDB Manual.

You can also use a favorite programming language (e.g., Java) or environment (e.g., NodeJS) using appropriate driver software to write a program to perform the copy - this might involve using find and insert operations or another method. This find-insert can be performed from the mongo shell too.

You can also do the collection copy using GUI programs like MongoDB Compass.

Using pymongo, you need to have both databases on same mongod, I did the following:

db = original database
db2 = database to be copied to

cursor = db["<collection to copy from>"].find()
for data in cursor:
    db2["<new collection>"].insert(data)

I know this question has been answered however I personally would not do @JasonMcCays answer due to the fact that cursors stream and this could cause an infinite cursor loop if the collection is still being used. Instead I would use a snapshot():

http://www.mongodb.org/display/DOCS/How+to+do+Snapshotted+Queries+in+the+Mongo+Database

@bens answer is also a good one and works well for hot backups of collections not only that but mongorestore does not need to share the same mongod.

This might be just a special case, but for a collection of 100k documents with two random string fields (length is 15-20 chars), using a dumb mapreduce is almost twice as fast as find-insert/copyTo:

db.coll.mapReduce(function() { emit(this._id, this); }, function(k,vs) { return vs[0]; }, { out : "coll2" })

If RAM is not an issue using insertMany is way faster than forEach loop.

var db1 = connect('<ip_1>:<port_1>/<db_name_1>')
var db2 = connect('<ip_2>:<port_2>/<db_name_2>')

var _list = db1.getCollection('collection_to_copy_from').find({})
db2.collection_to_copy_to.insertMany(_list.toArray())

Many right answers here. I would go for mongodump and mongorestore in a piped fashion for a large collection:

mongodump --db fromDB --gzip --archive | mongorestore --drop --gzip --archive --nsFrom "fromDB.collectionName" --nsTo "toDB.collectionName"

although if I want to do quick copy, its slow but it works:

use fromDB 
db.collectionName.find().forEach(function(x){
   db.getSiblingDB('toDB')['collectionName'].insert(x);
});"

This won't solve your problem but the mongodb shell has a copyTo method that copies a collection into another one in the same database:

db.mycoll.copyTo('my_other_collection');

It also translates from BSON to JSON, so mongodump/mongorestore are the best way to go, as others have said.

In case some heroku users stumble here and like me want to copy some data from staging database to the production database or vice versa here's how you do it very conveniently (N.B. I hope there's no typos in there, can't check it atm., I'll try confirm the validity of the code asap):

to_app="The name of the app you want to migrate data to"
from_app="The name of the app you want to migrate data from"
collection="the collection you want to copy"
mongohq_url=`heroku config:get --app "$to_app" MONGOHQ_URL`
parts=(`echo $mongohq_url | sed "s_mongodb://heroku:__" | sed "s_[@/]_ _g"`)
to_token=${parts[0]}; to_url=${parts[1]}; to_db=${parts[2]}
mongohq_url=`heroku config:get --app "$from_app" MONGOHQ_URL`
parts=(`echo $mongohq_url | sed "s_mongodb://heroku:__" | sed "s_[@/]_ _g"`)
from_token=${parts[0]}; from_url=${parts[1]}; from_db=${parts[2]}
mongodump -h "$from_url" -u heroku -d "$from_db" -p"$from_token" -c "$collection" -o col_dump
mongorestore -h "$prod_url" -u heroku -d "$to_app" -p"$to_token" --dir col_dump/"$col_dump"/$collection".bson -c "$collection"

You can always use Robomongo. As of v0.8.3 there is a tool that can do this by right-clicking on the collection and selecting "Copy Collection to Database"

For details, see http://blog.robomongo.org/whats-new-in-robomongo-0-8-3/

This feature was removed in 0.8.5 due to its buggy nature so you will have to use 0.8.3 or 0.8.4 if you want to try it out.

use "Studio3T for MongoDB" that have Export and Import tools by click on database , collections or specific collection download link : https://studio3t.com/download/

The simplest way to import data from the existing MongoDB atlas cluster DB is using mongodump & mongorestore commands.

To create the dump from existing DB you can use:

mongodump --uri="<connection-uri>"

There are other options for connection which can be lookup here: https://www.mongodb.com/docs/database-tools/mongodump/

After the dump is successfully created in a dump/ directory, you can use import that data inside your other db like so:

mongorestore --uri="<connection-uri-of-other-db>" <dump-file-location>

Similarly for mongorestore, there are other connection options that can be looked up along with commands to restore specific collections: https://www.mongodb.com/docs/database-tools/mongorestore/

The dump file location will be inside the dump directory. There may be a subdirectory with the same name as DB name which you dumped. For example if you dumped test DB, then dump file location would be /dump/test

Starting in version 4.2, MongoDB removes the deprecated copydb command and clone command.

As an alternative, users can use mongodump and mongorestore (with the mongorestore options --nsFrom and --nsTo).

For example, to copy the test collection from source database to the target database, you can:

1. Use mongodump to dump the test collection from source database to an archive test.agz:

mongodump --gzip --archive=/backup/path/to/test.agz --db=source --collection=test

2. Use mongorestore with --nsFrom and --nsTo to restore (with database name change) from the archive:

mongorestore --gzip --archive=/backup/path/to/test.agz --nsFrom='source.test' --nsTo='target.test'

NOTE: Provide authentication, if necessary, with the --uri parameter if MongoDB is running on an external instance, or a combination of the --username and --password parameters if MongoDB is running on a local instance.

Reference: mongodump — MongoDB Database Tools

I found it easy to export collection data in MongoDB Compass, which is free, and then import it (ADD DATA button) via MongoDB Compass to another db collection

In my case, I had to use a subset of attributes from the old collection in my new collection. So I ended up choosing those attributes while calling insert on the new collection.

db.<sourceColl>.find().forEach(function(doc) { 
    db.<newColl>.insert({
        "new_field1":doc.field1,
        "new_field2":doc.field2,
        ....
    })
});`

To copy a collection (myCollection1) from one database to another in MongoDB,

**Server1:**
myHost1.com 
myDbUser1
myDbPasword1
myDb1
myCollection1

outputfile:
myfile.json 

**Server2:**
myHost2.com 
myDbUser2
myDbPasword2
myDb2
myCollection2 

you can do this:

mongoexport  --host myHost1.com --db myDb1 -u myDbUser1  -p myDbPasword1 --collection myCollection1   --out  myfile.json 

then:

mongoimport  --host myHost2.com --db myDb2 -u myDbUser2  -p myDbPasword2 --collection myCollection2   --file myfile.json 

Another case , using CSV file:

Server1:
myHost1.com 
myDbUser1
myDbPasword1
myDb1
myCollection1
fields.txt
    fieldName1
    fieldName2

outputfile:
myfile.csv

Server2:
myHost2.com 
myDbUser2
myDbPasword2
myDb2
myCollection2

you can do this:

mongoexport  --host myHost1.com --db myDb1 -u myDbUser1  -p myDbPasword1 --collection myCollection1   --out  myfile.csv --type=csv

add clolumn types in csv file (name1.decimal(),name1.string()..) and then:

mongoimport  --host myHost2.com --db myDb2 -u myDbUser2  -p myDbPasword2 --collection myCollection2   --file myfile.csv --type csv --headerline --columnsHaveTypes

You could use the $out aggregation function to copy everything to another table.

https://www.mongodb.com/docs/manual/reference/operator/aggregation/out/

I came here looking for a way to transfer a collection, so thanks to Anuj Gupta for the second part of his solution, based on db.runCommand({renewCollection.... Similar kudos to Alexander Makarov's aggregate solution, and particularly to C0_42's comment.

For the rest, I see many solutions based on one-by-one read-write, which are what I would call, from the privileged standpoint of late 2023, "Winter Code". All those extra CPU cycles sure keep us warm... This includes the forEach solutions, explicit, disguised by cursor or initializeUnorderedBulkOp.

As for foreign tools, I don't really think that dump / restore or export / import are the ideal solutions. These work around the issue, avoiding mongosh, which is not ideal. I extend this assessment to recommendations such as Studio3T. Although I am a Python developer, resorting to pymongo seems to me like yet another workaround for those who refuse to learn mongosh, which is 99.7% good old JavaScript. Furthermore, the pymongo solution posted here also reads and inserts one by one.

On this same note, I found an online article here that on late May 2023 still suggests the extinct collection method copyTo, together with a bunch of scattered mentions (like the forEach or the aggregate) that are never developed into the theme of the title: "How to Copy a DB and a Collection?". Quite useless and worse: it's part of an online course, so useless and irresponsible. Watch out for responses here recommending both this method and db.copyDatabase. If your pet is a T-Rex, I guess your Mongo still has these.

My solution is similar to what I saw from Uday Krishna's post. I just made it as a function:

function transfer(collection, sourceDb, target_db) {
    db.getSiblingDB(targetDb).getCollection(collection).insertMany(
        db.getSiblingDB(sourceDb).getCollection(collection).find().toArray()
    )
}

Notice how this solution does not even force you to be using any of the DBs involved. The trick here is to do the .toArray() at the end, so that the result can be used as argument to insertMany.

Switch to the source database

use sourceDB;

Fetch all documents from the source collection

let documents = db.sourceCollection.find().toArray();

Switch to the target database

use targetDB;

Insert the documents into the target collection

db.targetCollection.insertMany(documents);

This can be done using Mongo's db.copyDatabase method:

db.copyDatabase(fromdb, todb, fromhost, username, password)

Reference: http://docs.mongodb.org/manual/reference/method/db.copyDatabase/