CODEWITHSUNDEEP
mongodbmeteor
Vice Sallés
Vice Sallés

Reputation: 97

Meteor collection sort by $size issue

This is about likes and dislikes on comments. I'd like to sort comments by likeness, so a comment with more likes will appear first. The issue is that comments with dislikes appear before than comments with no dislikes.

What i want:

What I'm actually getting:

My mongo query on my meteor helper:

Missatges.find({ topic: 'xxx' }, { sort: { like:{ $size: -1}, dislike:{ $size: 1}, date: -1 } }).fetch();

Note that I use $size because like and dislike are arrays of user _id's. Here my comment schema:

author: {
    type: String

},
authorId: {
    type: SimpleSchema.RegEx.Id
}
isAnswer: {
    type: Boolean
},
parentId: {
    type: SimpleSchema.RegEx.Id,
    optional: true
},
date: {
    type: Date
},
topic: {
    type: String
},
likes: {
    type: [SimpleSchema.RegEx.Id]
},
dislikes: {
    type: [SimpleSchema.RegEx.Id]
},
answers: {
    type: [SimpleSchema.RegEx.Id],
    optional: true
},
text: {
    type: String,
    max: 900,        
}

Upvotes: 1

Views: 102

Answers (1)

David Weldon
David Weldon

Reputation: 64312

According to the answer to this question you can't use $size to sort in mongo. One solution is to fetch the matching documents and sort them in the helper. Here's an example (note this is untested and may require some tweaking):

Template.something.helpers({
  sortedThings: function () {
    return Missatges
      .find({ topic: 'xxx' })
      .fetch()
      .sort(function (b, a) {
        var al = a.likes.length;
        var ad = a.dislikes.length;
        var bl = a.likes.length;
        var bd = a.dislikes.length;
        var d1 = a.date;
        var d2 = b.date;

        // compare by likes
        if (al > bl) return 1;
        if (al < bl) return -1;

        // compare by dislikes
        if (ad < bd) return 1;
        if (ad > bd) return -1;

        // compare by date
        if (d1 > d2) return 1;
        if (d1 < d2) return -1;

        // they are equal
        return 0;
      });
  },
});

Upvotes: 1

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