Mongoid，按名称和编号聚合模型

Question

我有一个名为 Shop 的模型，它有 name、image。有可能会有多个同名店铺。

例如，如果我有这些商店：

 [{_id: "1", name: "Shop A", image: "ImageShopA.jpg"},
  {_id: "2", name: "Shop A", image: "ImageShopA1.jpg"},
  {_id: "3", name: "Shop B", image: "ImageShopB.jpg"},
  {_id: "4", name: "Shop B", image: "ImageShopB1.jpg"},
  {_id: "5", name: "Shop C", image: "ImageShopC.jpg"}]

我想得到这样的结果：

 [{name: "Shop A", ids: ["1", "2"], image: "ImageShopA.jpg"}, 
  {name: "Shop B", ids: ["3", "4"], image: "ImageShopB.jpg"},
  {name: "Shop C", ids: ["5"], image: "ImageShopC.jpg"}]

它创建 JSON 个对象，这些对象具有按 name 分组的分组模型的 ID，并获取第一个找到的模型的图像。

是否可以通过聚合来做到这一点？

Answer 1

是的，有可能。如果您运行 mongo shell 中的以下聚合管道具有给定的数据样本

db.collection.aggregate([
    {
        "$sort": {
            "_id": 1
        }
    },
    {
        "$group": {
            "_id": "$name",
            "ids": {
                "$push": "$_id"
            },
            "image": {
                "$first": "$image"
            }
        }
    },
    {
        "$project": {
            "name": "$_id", "ids": 1, "image": 1
        }
    }
])

你会得到想要的结果：

/* 0 */
{
    "result" : [ 
        {
            "_id" : "Shop C",
            "ids" : [ 
                "5"
            ],
            "image" : "ImageShopC.jpg",
            "name" : "Shop C"
        }, 
        {
            "_id" : "Shop B",
            "ids" : [ 
                "3", 
                "4"
            ],
            "image" : "ImageShopB.jpg",
            "name" : "Shop B"
        }, 
        {
            "_id" : "Shop A",
            "ids" : [ 
                "1", 
                "2"
            ],
            "image" : "ImageShopA.jpg",
            "name" : "Shop A"
        }
    ],
    "ok" : 1
}

您需要将其转换为适当的ruby实现

Mongoid，按名称和编号聚合模型

Mongoid, aggregate models by name and number

ruby

ruby-on-rails

mongodb

mongoid