Filter events

Receive only the events you care about with a pipeline in watch.

Receive only the events you care about by passing a pipeline to watch. The filter runs on the server, so the other events do not travel over the network.

Requirements

A user with the find and changeStream privileges on what you watch.

Filter by type and by field

JavaScript

const stream = db.orders.watch([
  { $match: { operationType: "update", "updateDescription.updatedFields.status": "paid" } },
  { $project: { documentKey: 1, "updateDescription.updatedFields": 1 } },
]);

Bring the whole document

JavaScript

const stream = db.orders.watch([], { fullDocument: "updateLookup" });

Check

With the stream open, an updateOne that changes the status to paid produces an event and one that changes another field does not.

Common problems

A $project that removes _id leaves the event without a resume token and the stream fails.