what’s the namespace ?

[cmfunc]

this namespace is mongodb's collection and field ?
in this example, namespace == "users.users" ,namespace == "users.status", "users" is collection name? "status" is mongo document's field name?

func PipeBuilder(namespace string, changeStream bool) ([]interface{}, error) {

	// to build your pipelines for change events you will want to reference
	// the MongoDB reference for change events at 
	// https://docs.mongodb.com/manual/reference/change-events/

	// you will only receive changeStream == true when you configure gtm with
	// ChangeStreamNS (requies MongoDB 3.6+).  You cannot build pipelines for
	// changes using legacy direct oplog tailing

	if namespace == "users.users" {
		// given a set of docs like {username: "joe", email: "joe@email.com", amount: 1}
		if changeStream {
			return []interface{}{
				bson.M{"$match": bson.M{"fullDocument.username": "joe"}},
			}, nil
		} else {
			return []interface{}{
				bson.M{"$match": bson.M{"username": "joe"}},
			}, nil
		}
	} else if namespace == "users.status" && changeStream {
		// return a pipeline that only receives events when a document is 
		// inserted, deleted, or a specific field is changed. In this case
		// only a change to field1 is processed.  Changes to other fields
		// do not match the pipeline query and thus you won't receive the event.
		return []interface{}{
			bson.M{"$match": bson.M{"$or": []interface{} {
				bson.M{"updateDescription": bson.M{"$exists": false}},
				bson.M{"updateDescription.updatedFields.field1": bson.M{"$exists": true}},
			}}},
		}, nil
	}
	return nil, nil
}

[rwynn]

In this case the namespace is database + . + collection. So users is a database and both users and status are MongoDB collections in that database.

This example also references fields username and field1 within those collections.