🦸 Saving to a Collection

You can export the result of an aggregation pipeline to a different DB/collection. To do that, just add a last aggregation stage to your pipeline:

Atlas UI

Run this from the source collection

[{ $out: { db: "<output-db>", coll: "<output-collection>" } }]

MongoDB Shell

db.sourceCollection.aggregate[{ $out: { db: "<output-db>", coll: "<output-collection>" } }]

You can omit the db attribute, and the new collection will be created in the current DB.

{ $out: "<output-collection>" }

👐 Create a copy of the books with exactly 100 pages and output as a new collection named OneHundredPagesBooks.

Answer

Atlas UI

[
    {$match: {pages: 100}},
    {$out: "OneHundredPagesBooks"}
]

MongoDB Shell

let oneHundredPagesBooks = {$match: {pages: 100}};
let saveToNewCollection = {$out: "OneHundredPagesBooks"}

db.books.aggregate([
    oneHundredPagesBooks,
    saveToNewCollection
]);

After running this, we should see a new collection with:

show collections