mongodb - 在 mongoDB 预测中添加新字段

Question

我有一个如下所示的 mongo 系列(商店详细信息)...

{
    _id: "",
    storeName: "store1",
    items: [
        {
            itemName: "mongo",
            itemPrice: 20,
            itemAvailablity: 100 
        },
        {
            itemName: "apples",
            itemPrice: 50,
            itemAvailablity: 70 
        }
    ]
},
{
    _id: "",
    storeName: "store2",
    items: [
        {
            itemName: "banana",
            itemPrice: 10,
            itemAvailablity: 30 
        },
        {
            itemName: "apple",
            itemPrice: 45,
            itemAvailablity: 90 
        }
    ]
},
{
    _id: "",
    storeName: "store3",
    items: [
        {
            itemName: "apple",
            itemPrice: 10,
            itemAvailablity: 30 
        },
        {
            itemName: "mongo",
            itemPrice: 30,
            itemAvailablity: 50 
        }
    ]
}

根据上述数据，我想获取特定商品的详细信息以及商店名称。

如果我想从所有商店获取“mongo”详细信息，那么我的预期输出将是这样的

[
    {
        itemName: "mongo",
        itemPrice: 20,
        itemAvailablity: 100,
        storeName: "store1"
    },
    {
        itemName: "mongo",
        itemPrice: 30,
        itemAvailablity: 50,
        storeName: "store3" 
    }
]

我尝试使用不同的 mongo 聚合查询，但没有得到预期的输出

谁能帮我解决这个问题

谢谢

Answer 1

您可以通过此聚合实现此目的:

db.collection.aggregate([
  {
    $project: {
      storeName: "$$CURRENT.storeName",
      items: {
        $filter: {
          input: "$items",
          as: "item",
          cond: { $eq: ["$$item.itemName","mongo"] }
        }
      }
    }
  },
  { $unwind: "$items" },
  { $addFields: { "items.storeName": "$storeName"} },
  { $replaceRoot: { newRoot: "$items" }}
])

可以看到working here