ej9.mongodb

/**
 * Ejercicio 9:
 *      Crear una vista con los 5 géneros con mayor cantidad de comentarios, junto con la
cantidad de comentarios.
 */

use('mflix');

pipeline_operation = [
  {
    $lookup: {
      from: 'comments',
      localField: '_id',
      foreignField: 'movie_id',
      as: 'comment_data'
    }
  },
  {
    $addFields: {
      amount_comments: {
        $size: '$comment_data'
      }
    }
  },
  {
    $unwind: '$genres'
  },
  {
    $group: {
      _id: '$genres',
      amount_comments: {
        $sum: '$amount_comments'
      }
    }
  },
  {
    $sort: {
      amount_comments: -1
    }
  },
  {
    $limit: 5
  },
  {
    $project: {
      _id: 0,
      genre: '$_id',
      amount_comments: '$amount_comments'
    }
  }
];

db.createView(
  'top5_commented_genres',
  'movies',
  pipeline_operation
);

db.top5_commented_genres.find({}).pretty();