Nested array query does not work with Mongoose

Question

I have a mongo documnet of

{
    "locationId": "5f2084f756dc2428e96fcda4",
    "information": [{
        "category": ["5e5150c6c52a3904b74d6ff7"],     
        "date": {
            "$date": {
                "$numberLong": "1601407317343"
            }
        },
        "private": true
    }, {     
     "category": ["5e5150c6c52a3904b74d6ff7"], 
        "date": {
            "$date": {
                "$numberLong": "1601407317343"
            }
        },
        "private": false
    },
    }],
}

So far, what I have is to query the nested array.

const f = await info.aggregate([
  {
    $match: {
      $and: [
          {'locationId': '5f2084f756dc2428e96fcda4'},
          {'information.private': true}
      ]
    },
  },
]);

I am trying to query information.private = true. However, I receive both 'private: false' and 'private: true'. The outcome is

[
  {
    "_id": ObjectId("5a934e000102030405000000"),
    "information": [
      {
        "category": [
          "5e5150c6c52a3904b74d6ff7"
        ],
        "date": ISODate("2020-09-29T19:21:57.343Z"),
        "private": true
      },
      {
        "category": [
          "5e5150c6c52a3904b74d6ff7"
        ],
        "date": ISODate("2020-09-29T19:21:57.343Z"),
        "private": false
      }
    ],
    "locationId": "5f2084f756dc2428e96fcda4"
  }
]

I also tried with elemMatch and returns the same results. I'd looked up multiple answers on Stackoverflow but the dot notation and elemMatch do not work in this case. I know that I have done something wrong but I can't figure it out.

turivishal · Accepted Answer · 2020-10-04 07:50:41Z

1

You can try $filter,

$match your conditions
$addFields to add field information and $filter to iterate loop of array and get match documents as per condition

const f = await info.aggregate([
  {
    $match: {
      locationId: "5f2084f756dc2428e96fcda4",
      "information.private": true
    }
  },
  {
    $addFields: {
      information: {
        $filter: {
          input: "$information",
          cond: { $eq: ["$$this.private", true] }
        }
      }
    }
  }
])

Playground

Other option you can try $redact,

$match your condition
$redact Restricts the contents of the documents based on information stored in the documents themselves.

const f = await info.aggregate([
  { $match: { locationId: "5f2084f756dc2428e96fcda4" } },
  {
    $redact: {
      $cond: [{ $eq: ["$private", false] }, "$$PRUNE", "$$DESCEND"]
    }
  }
])

Playground

The find projection can accept aggregation expressions and syntax starting from MongoDB 4.4.

const f = await info.find([
  locationId: "5f2084f756dc2428e96fcda4",
  "information.private": true
},
{
  locationId: 1,
  information: {
    $filter: {
      input: "$information",
      cond: { $eq: ["$$this.private", true] }
    }
  }
})

Playground

edited Oct 4, 2020 at 7:50

answered Oct 1, 2020 at 5:16

turivishal

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5 Comments

chichi Over a year ago

Is there any reason why information.private is not working?

turivishal Over a year ago

Its a behavior, we can't access array element direct from match condition, match will just match condition. it will return whole document where array element match.

chichi Over a year ago

This happens when I use .find() as well. Do I always have to get the document and work it out?

turivishal Over a year ago

If you know there is single element in array and i want only one that, so you can use find({"information.private": true}, {"information.$": 1}) this will return single matching element from array, this is a only limited option, otherwise you can use aggregate() like my answer.

turivishal Over a year ago

Added one more option in find() method from mongodb4.4.

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