node.js - Populate + Aggregate in Mongoose -

this question has answer here:

• mongoose - how group , populate? 2 answers

i have 2 mongoose models: 1 transactions , other 1 tags associated them. in order implement reports, need aggregate code this:

transaction.aggregate([   { $unwind: '$tags' },   {     $group: {       _id: '$tags',       amount: {         $sum: '$amount'       }     }   } ]) 

question

this produces output containing _id , amount. now, i'd populate other fields (e.g. name) model, keeping calculated amount column. can within simple populate?

edit

the schemas models i'm describing:

var transactionschema = new schema({   description: {     type: string,     trim: true   },   amount: {     type: number,     required: 'forneça um valor',   },   date: {     type: date,     required: 'forneça uma data',     default: date.now   },   fromofx: {     type: boolean,     default: false   },   created: {     type: date,     default: date.now   },   correlated: {     type: boolean,     default: false   },   tags: [{     type: schema.types.objectid,     ref: 'transactiontag'   }],   correlates: [{     type: schema.types.objectid,     ref: 'transaction'   }],   user: {     type: schema.types.objectid,     ref: 'user'   } });  var transactiontagschema = new schema({   name: {     type: string,     required: 'forneça um nome',     trim: true   },   description: {     type: string,     trim: true   },   amount: {     type: number   } }); 

you can populate aggregation after fetched data mongodb. this:

// aggregate query question transaction.aggregate([{                             $unwind: '$tags'                         }, {                             $group: {                                 _id: '$tags',                                 amount: {                                     $sum: '$amount'                                 }                             }                         }])     .exec(function(err, transactions) {         // don't forget error handling         // callback transactions         // assuming having tag model         tag.populate(transactions, {path: '_id'}, function(err, populatedtransactions) {             // populated translactions inside populatedtransactions         });     });