MongoDB query with elemMatch for nested array data matching from inside objects

Question

MongoDB query with elemMatch for nested array data matching from inside objects. Here we have three project objects and each contains an array of exams with multiple objects. Here when "project_id" : ObjectId("5b6959e3dc68d21c6613c82d") , The "exams" array contain two times "writer.user_id":ObjectId("5b6959e3dc68d21c6613c77d") how could i get these two data filtered from the first project object ?

db.exams.insert([{
"project_id" : ObjectId("5b6959e3dc68d21c6613c82d"),
"exams" : [ 
    {
        "allotment_type" : "manual",
        "exam_id" : 1,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77d"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 2,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77e"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 3,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77d"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }]

},
{
"project_id" : ObjectId("5b6959e3dc68d21c6613c82e"),
"exams" : [ 
    {
        "allotment_type" : "manual",
        "exam_id" : 1,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77d"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 2,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77e"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 3,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77c"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }]

},
{
"project_id" : ObjectId("5b6959e3dc68d21c6613c82f"),
"exams" : [ 
    {
        "allotment_type" : "manual",
        "exam_id" : 1,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77d"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 1,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 2,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77e"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 2,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }, 
    {
        "allotment_type" : "manual",
        "exam_id" : 3,
        "topic" : "something",
        "word_count" : 5,
        "key_word_density" : 2,
        "writer" : {
            "user_id" : ObjectId("5b6959e3dc68d21c6613c77c"),
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "editor" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        },
        "manager" : {
            "user_id" : 3,
            "versions" : [ 
                {
                    "id" : 1,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 2,
                    "file_path" : "abcd"
                }, 
                {
                    "id" : 3,
                    "file_path" : "abcd"
                }
            ]
        }
    }]

}]);

score 1 · Answer 1 · answered Aug 07 '18 at 17:33

1

You can try with $filter aggregation

db.collection.aggregate([
  { "$project": {
    "exams": {
      "$filter": {
        "input": "$exams",
        "as": "exam",
        "cond": {
          "$eq": [ "$$exam.writer.user_id", ObjectId("5b6959e3dc68d21c6613c77d") ]
        }
      }
    }
  }}
])

answered Aug 07 '18 at 17:33

Ashh

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Thanks. Perfect solution. – ABDUL JAMAL Aug 07 '18 at 17:47
Can we do the same by using $elemMatch ? – ABDUL JAMAL Aug 07 '18 at 17:48
`$elemMatch` always returns first matching element not all matching elments – Ashh Aug 07 '18 at 17:51
Thanks for your valid replay. Please help me in this also! , if I need to pass the project_id where should I can pass?. like one more condition where project_id= ObjectId("") – ABDUL JAMAL Aug 07 '18 at 17:55
Hi Anthony Winzlet, am a beginner in MongoDB. I found that we can use $match data with aggregation. { $match:{"project_id" : ObjectId("5b6959e3dc68d21c6613c82d")} }, Once again thanks a lot.. – ABDUL JAMAL Aug 07 '18 at 18:22
Yes you can use `$match` on the first stage before `$project` – Ashh Aug 08 '18 at 02:44

MongoDB query with elemMatch for nested array data matching from inside objects

1 Answers1