CODEWITHSUNDEEP
node.jsmongodbmongodumpmongoexport
Omprakash Amarwal
Omprakash Amarwal

Reputation: 41

How to export a single field from a collection in MongoDB?

I want to export a single field from a single collection. Like collection name is products and field name is tag.
All tag will create new collection. I have tried this command: 

mongodump --host 192.168.1.46 --port 27017 --db myDb --collection products --fields tag -o bson  --out C:\Users\Desktop\tag

Upvotes: 0

Views: 1611

Answers (2)

Kevin Smith
Kevin Smith

Reputation: 14436

So lets start by inserting some products in to our collection:

db.products.insertMany([
    { name: 'TV', tags: ['livingroom', 'electronics']},
    { name: 'Radio', tags: ['bedroom', 'electronics']},
    { name: 'Computer', tags: ['bedroom', 'electronics']}
]);

{
        "acknowledged" : true,
        "insertedIds" : [
                ObjectId("586bae0ec5a9a94b2674943d"),
                ObjectId("586bae0ec5a9a94b2674943e"),
                ObjectId("586bae0ec5a9a94b2674943f")
        ]
}

We can now write a simple aggreation query to go though all the documents

db.products.aggregate([
    {$unwind: '$tags'},
    {$group: {_id: '$tags' }},
    {$out: 'productTags'}
]);

The {$unwind: '$tags'} will deconstruct the tags array field in to a document for each tag. Then the {$group: {_id: '$tags' }} will group each item and create a new document for each tag. Then the {$out: 'productTags'} will create us a productTags collection with the output of the documents.

now if we query the productTags collection we'll get the following output:

> db.productTags.find()
{ "_id" : "bedroom" }
{ "_id" : "electronics" }
{ "_id" : "livingroom" }

Upvotes: 1

Sourbh Gupta
Sourbh Gupta

Reputation: 833

mongodump doesn't support the selected field's backup. But you can use mongoexport/mongoimport to backup selected fields as:

mongoexport -c test --db testing -f key --out dump.json

Upvotes: 1

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