CODEWITHSUNDEEP
mongodbloopbackjsstrongloop
Carlos Chacon
Carlos Chacon

Reputation: 239

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

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

Upvotes: 2

Views: 193

Answers (3)

smile
smile

Reputation: 102

Creating a function inside our models

MyModel.observe('access', function logQuery(ctx, next) {
        Release.find({
            where: {
                release_id: 4
            }
        });
    });

Upvotes: 0

A.Z.
A.Z.

Reputation: 1648

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

Upvotes: 2

Harshit Laddha
Harshit Laddha

Reputation: 2124

According to the strongloop docs - https://docs.strongloop.com/display/public/LB/Querying+data

It provides ability to add multiple options for querying, filtering, limiting data on both REST endpoints as well as in Model Methods.

You can limit the fields in output in a remote method like this - 

Release.find(
   { fields : {"epoch_time":true} 
}, function(err, releases) {
   // ... your code here
} );

Or you can do it in operation hooks like this as specified in https://docs.strongloop.com/display/public/LB/Operation+hooks - 

MyModel.observe('access', function logQuery(ctx, next) {
  console.log('Accessing %s matching %s', ctx.Model.modelName, ctx.query.where);
  next();
});

Upvotes: 0

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