Unable to use $elemMatch in aggregation

Question

As the title suggests I am unable to use $elemMatch inside aggregate. I have attached my code below, and I would like to know if there is an alternative to this code. I'm trying to match and get all the elements of an array.

db.collection.aggregate([
  {
    $match: {
      s: "A",
      $or: [
        {
          id: "123"
        }, 
        {
          name: "Raj"
        }
      ],
      condition: {
        $elemMatch: {
          $and: [
            {
              "depend.id": "123",
              "depend.ques": "test ques"
            }, 
            {
              depend: {
                $size: 1
              }
            }
          ]
        }
      }
    }
  },
  {
    $lookup: {
      from: "categories",
      localField: "category",
      foreignField: "_id",
      as: "category"
    }
  },
  {
    $unwind: "$category"
  }
])

Sample document:

{
  "_id" : ObjectId("5d723e34ef5e6630fde5b71d"),
  "id" : 1,
  "name" : "Raj",
  "category" : 123,
  "condition" : [
    {
      "depend" : [
        {
          "id" : 1,
          "ques" : "test ques"
        }
      ]
    },
    {
      "depend" : [
        {
          "id" : 2,
          "ques" : "test 2nd ques"
        }
      ]
    }
  ]
}

The sample document should be matched with the above query.

Answer 1

This Query is perfectly working on your data.

db.getCollection('stackans').aggregate([
      {
        $match: {
          $or: [
            {
              id: 1
            }, 
            {
              name: "Raj"
            }
          ],
          condition: {
            $elemMatch: {
              $and: [
                {
                  "depend.id": 1,
                  "depend.ques": "test ques"
                }, 
                {
                  depend: {
                    $size: 1
                  }
                }
              ]
            }
          }
        }
      } ,{
        $lookup: {
          from: "categories",
          localField: "category",
          foreignField: "_id",
          as: "category"
        }
      }
    ])

Answer 2

Issues:

• There is no s field in the sample document and you are applying a filter on in i.e. s: "A"
• Both id and depend.id are numeric but are matched with string literals
• There is no document in condition array with depend.id as 123

Please refer the following query:

db.collection.aggregate([
  {
    $match:{
      $or:[
        {
          "id":123
        },
        {
          "name":"Raj"
        }
      ],
      "condition":{
        $elemMatch:{
          $and:[
            {
              "depend.id":1,
              "depend.ques": "test ques"
            },
            {
              "depend":{
                $size:1
              }
            }
          ]
        }
      }
    }
  }
]).pretty()