How to QUERY a deeply nested json document?

问题

I have imported a huge json file into mongoDB. It has imported as one whole document (with one _id). My json looks like this:

       {
  "_id": ObjectId("bas8adsfa832034821"),
  "Spele": {
    "Laiks": "2017/01/11",
    "Skatitaji": 6740,
    "Vieta": "Newlands Stadium",
    "T": [
      {
        "Uzvards": "Antamo",
        "Vards": "Dennis"
      },
      {
        "Uzvards": "Prompa",
        "Vards": "Pedro"
      }
    ],
    "Komanda": [
      {
        "Nosaukums": "Barcelona",
        "Speletaji": {
          "Speletajs": [
            {
              "Loma": "V",
              "Nr": 16,
              "Uzvards": "Sam",
              "Vards": "Sidney"
            },
            {
              "Loma": "A",
              "Nr": 17,
              "Uzvards": "Cisovsky",
              "Vards": "Marian"
            }
          ]
        }
      }
    ]
  }
}

So with every query I try, it returns the whole document. Setting specific parameters don't help like: db.games.find({"Spele.Komanda.Speletaji.Speletajs.Nr" : 16})

When I'd expect it to return

{ "Loma" : "V",
   "Nr" : 16,
   "Uzvards" : "Sam"
   "Vards" : ""Sidney"
}

But it returns the whole document instead. Maybe I'm not using the query right, or I have to provide every nested document with _id, but I don't know how. I can use mongo shell or PHP to do this.

回答1:

You can try below aggregation query.

$filter inner array and $arrayElemAt to project the matched element.

$map to output all matching Speletajs elements across all Kamadas.

$arrayElemAt to reduce to a single match. For multiple matches remove $arrayElemAt.

db.games.aggregate([
  {"$match":{"Spele.Komanda.Speletaji.Speletajs.Nr":16}},
  {"$project":{
    "Speletaji":{
      "$arrayElemAt":[
        {"$map":{
          "input":"$Spele.Komanda",
          "in":{
            "$arrayElemAt":[
              {"$filter":{
                "input":"$$this.Speletaji.Speletajs",
                "cond":{"$eq":["$$this.Nr",16]}

              }},
            0]
          }
        }},
      0]
    }
  }}
])

回答2:

This is because you only specify the query part of the .find({}) operation and not the projection part. This is the syntax of the .find({}):

db.collection.find({query}, {projection});

So your query should be more similar to something similar to:

db.games.find({"Spele.Komanda.Speletaji.Speletajs.Nr":16},{"Spele.Komanda.Speletaji.Speletajs":1});

However this will return more than what you want. To return preceiselly what you want you will need projection operators: https://docs.mongodb.com/manual/reference/operator/projection/

来源：https://stackoverflow.com/questions/48128835/how-to-query-a-deeply-nested-json-document

标签

php

json

mongodb

nested