如果 mongodb 中不存在，如何添加大子元素？答案

【问题标题】：How to add grand children elements if it do not exist in mongodb?如果 mongodb 中不存在，如何添加大子元素？
【发布时间】：2020-06-11 10:43:13
【问题描述】：

我需要向大子元素添加新元素。例如，我需要为现有产品添加新仓库。在此示例中，所有 size.wares 都有 LAX，但是产品“aaaa”、尺寸“42”和产品“bbbb”、尺寸“45”中缺少“NYC”

所以我需要检查所有产品及其尺寸，如果商品“NYC”存在，则添加新商品“NYC”

[
{
"_id": ObjectId("5db72c636309f84479ec0c7b"),
"productCode": "aaaa",
"brand": "Nike",
"image": "some.jpg",
"sizes": [
    {
    "_id": ObjectId("5db72c636309f84479ec0c7e"),
    "size": "41",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c80"),
        "ware": "LAX",
        "amount": 100
        },
        {
        "_id": ObjectId("5db72c636309f84479ec0c7f"),
        "ware": "NYC",
        "amount": 7
        }
    ]
    },
    {
    "_id": ObjectId("5db72c636309f84479ec0c7c"),
    "size": "42",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c7d"),
        "ware": "LAX",
        "amount": 16
        }
    ]
    }
]
},
{
"_id": ObjectId("5db72c636309f84479ec0c7X"),
"productCode": "bbbb",
"brand": "Nike",
"image": "some.jpg",
"sizes": [
    {
    "_id": ObjectId("5db72c636309f84479ec0c7D"),
    "size": "41",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c8G"),
        "ware": "LAX",
        "amount": 100
        },
        {
        "_id": ObjectId("5db72c636309f84479ec0c7R"),
        "ware": "NYC",
        "amount": 7
        }
    ]
    },
    {
    "_id": ObjectId("5db72c636309f84479ec0c7q"),
    "size": "45",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c7n"),
        "ware": "LAX",
        "amount": 16
        }
    ]
    }
]
}]

例如产品“bbbb”尺寸“45”

{
    "_id": ObjectId("5db72c636309f84479ec0c7q"),
    "size": "45",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c7n"),
        "ware": "LAX",
        "amount": 16
        }
    ]
    }

在“upsert”之后应该是这样的吗

{
    "_id": ObjectId("5db72c636309f84479ec0c7q"),
    "size": "45",
    "wares": [
        {
        "_id": ObjectId("5db72c636309f84479ec0c7n"),
        "ware": "LAX",
        "amount": 16
        },{
        "_id": ObjectId("5db72c636309f84479ec0c7x"),
        "ware": "NYC",
        "amount": 0
        }

    ]
    }

【问题讨论】：

标签： arrays mongodb updates

【解决方案1】：

会是这个：

db.collection.updateOne(
   { productCode: "bbbb" },
   {
      $push: {
         "sizes.$[item].wares": {
            _id: ObjectId("5db72c636309f84479ec0c7a"),
            ware: "NYC",
            amount: 0
         }
      }
   },
   { arrayFilters: [{ "item.size": "45" }] }
)

注意，为了避免重复，您可以使用$addToSet 而不是$push。

【讨论】：