Returning all comments of a specific user without other document fields using mongoose

Question

var mongoose = require('mongoose'); // defines the database schema for this object var schema = mongoose.Schema({ projectName : String, authorName : String comment : [{ id : String, authorName : String, authorEmailAddress : { type : String, index : true } }] }); 

})

 // Sets the schema for model var ProjectModel = mongoose.model('Project', schema); // Create a project exports.create = function (projectJSON) { var project = new ProjectModel({ projectName : projectJSON.projectName , authorName : projectJSON.authorName, comment : [{ id : projectJSON.comments.id, authorName : projectJSON.comments.authorName, authorEmailAddress : projectJSON.authorEmailAddress }); project.save(function(err) { if (err) { console.log(err); } else{ console.log("success"); } }); } 

Q: I would like to receive all comments (without other document fields) that the user made in all projects

My attempt:

 // assuming email address is unique per user, as user can always change displayName for instance exports.allCommentsByUser = function(userEmail, callback){ ProjectModel.find( {"comments.authorEmailAddress" : userEmail}, { "projectName" : 1, "comments.authorEmailAddress" : 1 }, callback); }; 

Answer 1

You can use the aggregation structure 2.2 for this type of query:

 ProjectModel.aggregate([ { // Only include the projectName and comments fields. $project: { 'projectName': true, 'comments': true, '_id': false } }, { // Get all project docs that contain comments by this user $match: { 'comments.authorEmailAddress': userEmail } }, { // Duplicate the project docs, one per comment. $unwind: '$comments' }, { // Filter that result to just the comments by this user $match: { 'comments.authorEmailAddress': userEmail } }], callback );