Move a collection from one DB to another DB within the same MongoDB instance

Question

I have many collections in database A. I want to copy some of them to database B in the same MongoDB.

I tried to copy whole database using db.copyDatabase('A', 'B'), but it has more than 300 GB data. It will take ages to copy and I just want to copy a few collections from database A to database B.

Does anyone know how can I do it?

Shaishab Roy · Accepted Answer · 2017-01-20 06:07:44Z

13

You can try it using mongo shell. you can copy collection from one db to another db using renameCollection. the renameCollection can run from admin database so first need to switch to admin db.

so ca follow bellow steps in mongo shell:

step-1: run this comment use admin

step-2: run bellow comment

db.runCommand({renameCollection:"sourcedb.sourceCollection",to:"targetdb.tragetCollection"})

for example:

use admin
db.runCommand({renameCollection:"funnel.countries",to:"test.countries"})

copied countries collection from funnel db to test db.

In background MongoDB will create dump for source collection and restore the dump automatically to target db collection

edited Jan 20, 2017 at 6:07

answered Jan 20, 2017 at 5:46

Shaishab Roy

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6 Comments

Emily Chen Over a year ago

It is working perfectly! Thank you so much . I thought renameCollection only works when you want to change the collection name!

Emily Chen Over a year ago

Also, I wonder will it work if i put different collections in one query, or I only can move one collection at each time. I am going to try

Bajal Over a year ago

This will move the collection, not a copy (as it is a rename)

Reed Over a year ago

It is a dump and restore. I just renamed a 3GB collection to another DB. It took a few minutes.

Ikar Pohorský Over a year ago

Note: collection indices are not preserved with this operation! You may want to re-create them.

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ares · Accepted Answer · 2017-01-20 05:42:24Z

4

Use mongodump to dump the collections:

mongodump  --db A --collection coll --out yourbackupdir

and then import the collections using mongorestore:

mongorestore --db B --collection coll yourbackupdir/

answered Jan 20, 2017 at 5:42

ares

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2 Comments

Emily Chen Over a year ago

Thanks for answering. But in my case , I just want to move few collections because it is too much to dump whole database.

Wernfried Domscheit Over a year ago

There is no need to store it to a file. Use STDOUT and STDIN: mongodump --db=A --collection=coll --archive=- | mongorestore --nsFrom="A.coll " --nsTo="B.coll " --archive=- Collections can be specified by wild-card characters.

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