Meteor Counts in Router Level Subscription

Question

I have a list that subscribes to posts publication with a limit.

Publication

Meteor.publish('posts', function(options) {
  check(options, {
    sort: Object,
    limit: Number
  });

  var posts = Posts.find({}, options);

  return posts;
});

within the list, I have items under each

list.html

{{#each posts}}
  {{> postItem}}
{{/each}}

within each postItem, I would like to count its comment number.

I believe the code for above would be

Template.postItem.helpers({
   commentsCount: function () {
    return Comments.find({postId: this._id }).count();
   }
});

The problem with this is that I would have to publish all of comments inside posts publication which would really be inefficient.

I would like to make a publication where I could subscribe to it within Template level for each postItems and just return the resulting Counts I tried tmeasday:publish-counts but I did not figure out how to make it work in my case, or even if it would be used in this scenario.

Answer 1

Option 1: Keep track number of comment in the Posts collection itself.

Each time new Comment inserted, update the counter:

Posts.update(
 { _id: String },
 { $inc: { commentsCount: 1 } }
)

This way you doesn't need to subscribe Comments just to get the count, which will involve multiple round trip to server.

Option 2: Use Meteor.methods and Meteor.call to return the number of comment for each Posts. Multiple round trip to server will occur.

Option 3: Use aggregation to $group and count no of comment on server and map it back to Posts on client.

Option 4: Reactive joins

I strongly recommend option #1 for performance and reactivity.