Projection

Return only the fields your application needs. Fetching fewer fields saves network and memory, above all with large documents.

Requirements

• A connection with a user that has read on the database.

Choose fields

db.orders.find({ status: "paid" }, { customer: 1, total: 1, _id: 0 });

Trim an array

db.orders.find({}, { lines: { $slice: 3 } });

Check

The returned documents carry only the fields you asked for. _id always comes out unless you exclude it with _id: 0.

Common problems

• The projection fails because it mixes included and excluded fields; only _id can be excluded next to included fields.

See also

• Query documents
• Anti-patterns