Query with double nested array of elements

Question

I am stuck at this. I'm trying to query two levels of nested documents with the index i.e [0]. Here's my mongoDb document.

[
  {
    "_id": ObjectId("5b8803a07078906483e2e8a9"),
    "vote": [
      [
        "a4d77175-250d-4990-bc1c-d79c8175c1f0",
        "5b82e2d1b47b3513f3f25854"
      ],
      [
        "a934cf1d-ecb1-4764-b8bb-9c3c40c1128d",
        "5b82e355b47b3513f3f25858"
      ]
    ],
    "election_id": ObjectId("5b82e3cfb47b3513f3f2585a"),
    "user_id": ObjectId("5b82e2d1b47b3513f3f25854"),
    "date": "Thu Aug 30 2018 17:48:00 GMT+0300 (EAT)",
    "__v": 0
  }
]

I'm trying to get to this value "a4d77175-250d-4990-bc1c-d79c8175c1f0" inside vote. I tried this to no avail.

exports.getVotesByPosts = (req, res, next) => {
  Vote.find({'vote[0][0]': req.params.id}, (err, vote) => {
    res.json(vote);
  }).sort( { date: -1 });
}

Thanks in advance for your help. Regards

do you know both the vote[0][0] and vote[0][1]?

mehta-rohan
– mehta-rohan

2018-09-08 13:52:13 +00:00
Commented Sep 8, 2018 at 13:52 — mehta-rohan
– mehta-rohan, Commented Sep 8, 2018 at 13:52

Ashh · Accepted Answer · 2018-09-08 13:51:57Z

1

You need to use $elemMatch query with the $eq operator

Vote.find({
  "vote": {
    "$elemMatch": {
      "$elemMatch": {
        "$eq": "a4d77175-250d-4990-bc1c-d79c8175c1f0"
      }
    }
  }
})

answered Sep 8, 2018 at 13:51

Ashh

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6 Comments

mehta-rohan Over a year ago

can we use positional character $ in that to fetch only matched array?

Ashh Over a year ago

$ is the projection operator we cannot use it to query.

mehta-rohan Over a year ago

yeah the question is can we use projection here

mehta-rohan Over a year ago

sir that's my question to you

Dng Over a year ago

Thanks Anthony Winzlet

|

Dng · Accepted Answer · 2018-09-08 14:29:23Z

0

Here's how i fixed it using Anthony's answer

    Vote.find({
      "vote": {
        "$elemMatch": {
          "$elemMatch": {
            "$eq": req.params.id
          }
        }
      }
    });

answered Sep 8, 2018 at 14:29

Dng

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