MongoDb Filter Array

问题

Data structure:

[{
  "_id": {
    "$oid": "5f1e91da1d840d673d159e69"
  },
  "product": [
    {
      "_id": "1",
      "name": "FirstWarehouseName1",
      "image": "FirstWarehousePhoto1",
      "manufacturer": "FirstWarehouseProducer1",
      "warehouse": "Warehouse1",
      "price": "32",
      "amount": 344
    },
    {
      "_id": "2",
      "name": "FirstWarehouseName2",
      "image": "FirstWarehousePhoto2",
      "manufacturer": "FirstWarehouseProducer2",
      "warehouse": "Warehouse1",
      "price": "12",
      "amount": 631
    },
    {
      "_id": "3",
      "name": "FirstWarehouseName3",
      "image": "FirstWarehousePhoto3",
      "manufacturer": "FirstWarehouseProducer3",
      "warehouse": "Warehouse1",
      "price": "66",
      "amount": 752
    }
  ],
  "_class": "pl.com.ttsw.intership.product_model.Products"
},{
  "_id": {
    "$oid": "5f1e91da1d840d673d159e6a"
  },
  "product": [
    {
      "_id": "1",
      "name": "SecondWarehouseName1",
      "image": "SecondWarehousePhoto1",
      "manufacturer": "SecondWarehouseProducerName1",
      "warehouse": "Warehouse2",
      "price": "32",
      "amount": 344
    },
    {
      "_id": "2",
      "name": "SecondWarehouseName2",
      "image": "SecondWarehousePhoto2",
      "manufacturer": "SecondWarehouseProducerName2",
      "warehouse": "Warehouse2",
      "price": "12",
      "amount": 631
    },
    {
      "_id": "3",
      "name": "SecondWarehouseName3",
      "image": "SecondWarehousePhoto3",
      "manufacturer": "SecondWarehouseProducerName3",
      "warehouse": "Warehouse2",
      "price": "66",
      "amount": 752
    }
  ],
  "_class": "pl.com.ttsw.intership.product_model.Products"
},{
  "_id": {
    "$oid": "5f1e91db1d840d673d159e6b"
  },
  "product": [
    {
      "_id": "1",
      "name": "ThirdWarehouseName1",
      "image": "ThirdWarehousePhoto1",
      "manufacturer": "ThirdWarehouse1",
      "warehouse": "Warehouse3",
      "price": "44",
      "amount": 123
    },
    {
      "_id": "2",
      "name": "ThirdWarehouseName2",
      "image": "ThirdWarehousePhoto2",
      "manufacturer": "ThirdWarehouse2",
      "warehouse": "Warehouse3",
      "price": "11",
      "amount": 442
    },
    {
      "_id": "3",
      "name": "ThirdWarehouseName3",
      "image": "ThirdWarehousePhoto3",
      "manufacturer": "ThirdWarehouse3",
      "warehouse": "Warehouse3",
      "price": "2",
      "amount": 2213
    }
  ],
  "_class": "pl.com.ttsw.intership.product_model.Products"
}]

IMG

I try too like this:

IMG2

ERROR

/////////////////////////////////////////////////////////////// I need filter array in array(products in warehouses) by their names; If I do without project response is Array with all products. Output results if (search By "Name3")

[{
  "_id": {
    "$oid": "5f1e91da1d840d673d159e69"
  },
  "product": [
    {
      "_id": "3",
      "name": "FirstWarehouseName3",
      "image": "FirstWarehousePhoto3",
      "manufacturer": "FirstWarehouseProducer3",
      "warehouse": "Warehouse1",
      "price": "66",
      "amount": 752
    }
  ]
},{
  "_id": {
    "$oid": "5f1e91da1d840d673d159e6a"
  },
  "product": [
    {
      "_id": "3",
      "name": "SecondWarehouseName3",
      "image": "SecondWarehousePhoto3",
      "manufacturer": "SecondWarehouseProducerName3",
      "warehouse": "Warehouse2",
      "price": "66",
      "amount": 752
    }
  ]
},{
  "_id": {
    "$oid": "5f1e91db1d840d673d159e6b"
  },
  "product": [
    {
      "_id": "3",
      "name": "ThirdWarehouseName3",
      "image": "ThirdWarehousePhoto3",
      "manufacturer": "ThirdWarehouse3",
      "warehouse": "Warehouse3",
      "price": "2",
      "amount": 2213
    }
  ]
}]

I tried all ways and I can't manage. ////////////////////////////////

回答1:

You can do

[{
    $unwind: {
        path: "$product",
        preserveNullAndEmptyArrays: false
    }
}, {
    $match: {
        "product.name": {
            $regex: "Name3"
        }
    }
}, {
    $group: {
        _id: "$_id",
        product: {
            $push: "$product"
        }
    }
}]

Working Mongo playground

回答2:

If you just filter an element in an array, even if only one of the element matches, the whole array will be returned, and nothing will be returned if there was no match. Therefore, you need to separate your array into different documents using the $unwind operator, and only after it, try to filter the results using $match.

The following query might solve your problem:

db.collection.aggregate([
  {"$unwind": "$product"},
  {"$match": {"product.name": "FirstWarehouseName1"}} // replace here with the name you want
])

Working mongoplayground

If I may, just a tip: You should store each product in a different document, although MongoDB is schemaless and allow us to have almost any format of document, remember that each document should contain the equivalent to one row of information in a regular relational database. Otherwise, you'll start to have these problems, and additionally, performance issues.

来源：https://stackoverflow.com/questions/63150083/mongodb-filter-array