Get total count of in array embedded documents for a MongoDB collection [duplicate]

manpreet Best Answer 3 years ago

 Here is an example MongoDB collection of articles with embedded comments:

{
  _id: 1,
  name: "article_1",
  comments: [
    { title: 'title_1_1', ... },
    { title: 'title_1_2', ... }
  ]
}
{
  _id: 2,
  name: "article_2",
  comments: [
    { title: 'title_2_1', ... },
    { title: 'title_2_2', ... },
    { title: 'title_2_3', ... }
  ]
}

How can I efficiently query for the total count of comments? The result should be 5 for the example above.