StrongLoop: does it support Limit Fields to Return from a Query for MongoDB databases?

Question

Does anyone know if strongloop supports limit fields to return from a Query for MongoDB databases? I think strongloop doesnt support all the MongoDB query features so I'm afraid this might not be supported.

This is what I want to achieve using strongloop:

https://docs.mongodb.org/v3.0/tutorial/project-fields-from-query-results/

MongoDB operations example (executed within the database):

Without Limiting the Fields:

> db.Releases.find({epoch_time: {$gte: 1451417675, $lt: 1483717675}})
{ "_id" : ObjectId("5682bbcbab755688f9bfd939"), "release_id" : 3, "event_id" : 1, "epoch_time" : 1451417675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93a"), "release_id" : 4, "event_id" : 2, "epoch_time" : 1452717675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93b"), "release_id" : 5, "event_id" : 2, "epoch_time" : 1453717675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93c"), "release_id" : 6, "event_id" : 3, "epoch_time" : 1461207675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93d"), "release_id" : 7, "event_id" : 3, "epoch_time" : 1461407675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93e"), "release_id" : 8, "event_id" : 4, "epoch_time" : 1461417675 }
{ "_id" : ObjectId("5682bbccab755688f9bfd93f"), "release_id" : 9, "event_id" : 1, "epoch_time" : 1472717675 }
{ "_id" : ObjectId("5682bbd1ab755688f9bfd940"), "release_id" : 10, "event_id" : 5, "epoch_time" : 1473717675 }

Limiting the fields:

> db.Releases.find({epoch_time: {$gte: 1451417675, $lt: 1483717675}},{_id:0,release_id:0,event_id:0})
{ "epoch_time" : 1451417675 }
{ "epoch_time" : 1452717675 }
{ "epoch_time" : 1453717675 }
{ "epoch_time" : 1461207675 }
{ "epoch_time" : 1461407675 }
{ "epoch_time" : 1461417675 }
{ "epoch_time" : 1472717675 }
{ "epoch_time" : 1473717675 }

I tried something like this in StrongLoop but I still get all the fields in the query.

Release.find({where: {...query expression...} },
  {_id:0,release_id:0,event_id:0},  //trying to limit return fields
  function (err, releases) {
  ...
  }
);

Thanks, Carlos

Answer 1

Yes, loopbackjs supports limiting fields in query. Diffrence between limiting fileds in mongodb and loopback query is that loopbackjs defaults return all fields to false when using fields filter. You have to explicitly say which fields you want query to return.

Release.find({where: {release_id : 4}, fields: {epoch_time: true}},  //return only epoch_time
  function (err, releases) {
  ...
  }
);

fields filter docs