Building a Meteor query in MongoDB using $in operator while handling duplicate values

Question

Building a Meteor query in MongoDB using $in operator while handling duplicate values

I have a collection of songs that I want to present to a user. Each song is associated with a specific id. The issue I am encountering is that some songs should be displayed multiple times. Currently, I am using the $in operator in my MongoDB query, but it only returns three unique song ids, limiting the number of objects returned to just three. Consequently, when I use spacebars to iterate over these objects in my template, I am unable to display the same song multiple times. Any guidance on how to resolve this would be greatly appreciated.

Current Song Display Order:

My Everything
This an That
Going off Again

Desired Song Display Order:

My Everything
My Everything
This an That
Going off Again

Below is the code snippet I am using:

Template.songList.helpers({
songs: function () {

  var idsOfSongs = ["cEbeGLR5ujCEFPtnH", "cEbeGLR5ujCEFPtnH", "qcRfAPeYMQycwodLA", "7oK4TKZiEfvZoC5Jz"]    
  return Songs.find({"_id":{$in: idsOfSongs}}).fetch();

  } 
});

Objects returned from Songs.find:

[Object, Object, Object]
0: Object
_id: "cEbeGLR5ujCEFPtnH"
album: "My Everything"
artist: "Ariana Grande"

1: Object
_id: "qcRfAPeYMQycwodLA"
album: "This an That"
artist: "Mark Miller"

2: Object
_id: "7oK4TKZiEfvZoC5Jz"
album: "Going off Again"
artist: "Pick up Sticks"

javascript mongodb meteor

Answer 1

Answer №1

@Blake Seven is correct in pointing out that mongo does not have native support for this operation. (However, a SQL database could handle this using an outer join or cross-product).

One approach to achieving this is:

Template.songList.helpers({
  songs: function () {
    var songIds = ["cEbeGLR5ujCEFPtnH", "cEbeGLR5ujCEFPtnH", "qcRfAPeYMQycwodLA", "7oK4TKZiEfvZoC5Jz"];  
    var songsWithCount = [];
    songIds.forEach(function(id){
      songsWithCount.push(Songs.findOne({_id: id})); 
    }
    return songsWithCount;
  } 
});

Answer 2

@Blake Seven is correct in pointing out that mongo does not have native support for this operation. (However, a SQL database could handle this using an outer join or cross-product).

One approach to achieving this is:

Template.songList.helpers({
  songs: function () {
    var songIds = ["cEbeGLR5ujCEFPtnH", "cEbeGLR5ujCEFPtnH", "qcRfAPeYMQycwodLA", "7oK4TKZiEfvZoC5Jz"];  
    var songsWithCount = [];
    songIds.forEach(function(id){
      songsWithCount.push(Songs.findOne({_id: id})); 
    }
    return songsWithCount;
  } 
});

Answer 3

Answer №2

To iterate through the array of songIDs, you can use {{#each}} and then within the loop, utilize {{#with}} to access each individual song.

{{#each songIds}}
    {{#with song}}
        <li><em>{{album}}</em> by {{artist}}</li>
    {{/with}}
{{/each}}

Template.songList.helpers({
    songIds: function () {
        return ["cEbeGLR5ujCEFPtnH", ...]
    },
    song: function () {
        return Songs.findOne({_id: this});
    }
});

Answer 4

To iterate through the array of songIDs, you can use {{#each}} and then within the loop, utilize {{#with}} to access each individual song.

{{#each songIds}}
    {{#with song}}
        <li><em>{{album}}</em> by {{artist}}</li>
    {{/with}}
{{/each}}

Template.songList.helpers({
    songIds: function () {
        return ["cEbeGLR5ujCEFPtnH", ...]
    },
    song: function () {
        return Songs.findOne({_id: this});
    }
});

Building a Meteor query in MongoDB using $in operator while handling duplicate values

Answer №1

Answer №2

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