CODEWITHSUNDEEP
node.jsmongodb
Goose
Goose

Reputation: 190

Using MongoDB $out aggregation operator in node.js

Does anybody know how one would go about using the $out operator to push the results of a MongoDB aggregation function into a new collection in node.js?

This is what I have:

var fs = require('fs');
var assert = require('assert');
var ObjectId = require('mongodb').ObjectID;
var MongoClient = require('mongodb').MongoClient
    , format = require('util').format;

var createGroups = function(db, callback) {
   db.collection('people').aggregate(
     [
       { $group: { "_id": "$code", "sendees" : {$push : "$email"}, "count": { $sum: 1 } } }

     ]
   ).toArray(function(err, result) {
     assert.equal(err, null);
     console.log(result);
     callback(result);

   });
};

MongoClient.connect('mongodb://localhost:12121/systest', function(err, db) {
  assert.equal(null, err);
  createGroups(db, function() {
      db.close();
  });
});

Which outputs to the console fine, exactly as I'd expect - but I'm having little luck trying to export this to a new collection.

Thanks!

Upvotes: 2

Views: 2473

Answers (3)

Goose
Goose

Reputation: 190

Thanks for your answers folks - both very helpful. As it happens I was using an outdated version of mongo from before $out came into being - but once I sorted this out and did as you suggested above it worked perfectly.

Upvotes: 0

chridam
chridam

Reputation: 103335

You could try use the mongo-aggregate-out package which saves aggregation results to a collection for Mongo versions < 2.6. If your MongoDB version is 2.6 or newer, the module would behave as passthrough and will use the native feature:

var aggregateOut = require('mongo-aggregate-out'),
    pipelineArray = [
       { 
           $group: { 
               "_id": "$code", 
               "sendees" : {$push : "$email"}, 
               "count": { $sum: 1 } 
           } 
       }
    ];

var createGroups = function(db, callback) {
    aggregateOut(db.collection('people'), pipelineArray, { out: "newCollection"}, 
        function (err) {
            assert.equal(err, null);
            var cur = db.collection('newCollection').find();
            callback(cur);
    });
};

Upvotes: 0

Pio
Pio

Reputation: 4064

You just need to supply $out in your aggregation. See the docs.

So your code should look like:

 db.collection('people').aggregate(
     [
       { 
         $group: {
           "_id": "$code", 
           "sendees" : {$push : "$email"}, 
           "count": { $sum: 1 } 
          } 
        },
        {
          $out: "collection name"
        }
     ]
   )

Upvotes: 1

Related Questions