Mongodb $match on objects field where the index is a known field

Question

Let's say I have an Document like so.

const User = {
    info: {
        id: 123,
    },
    data: {
        111:{},
        123:{value: 5},
        234:{value: 10},
    }
}

And I want to preform and aggregation that can check if 'data.123.value' is greater than 10.

Is something like that possible with mongo? This is what I have so far, but it's not working.

aggregate([
{
    $project: {
    UserId: '$info.id',
    }
},
{
    $match: {
        'data[$UserId].value: {$gt: 10},
    }
}
]

I can do some server side work to preform this operation, but i would be really cool if mongo could just do this for me.

Any help is appreciated!

Can You explain in detail what You want to achieve? Are You sure that this document example is correct one? What if You want just have users collection and `value: 10` and You want to get users that has value more than 10 ? — num8er, May 14 '18 at 22:00
I dummied up the document a little bit to simplify things. But I want to return all documents in the collection where their 'data' at the index of the 'info.id' is greater than 10. — caden311, May 14 '18 at 22:02
data can have other user info ids, so I need to index it by the info id for the given User doc. — caden311, May 14 '18 at 22:02
I think You should have 2 collections and models: 1. User (users collection), 2. UserData (user_data) and after that You can it using 2 requests to db: 1. get users id fields, 2. get user_data that has that object value. No-SQL databases does not like relational things and for that case You've to think different to achieve Your goal — num8er, May 14 '18 at 22:05
Presuming `var userId = '123'';` Then: ``{ "$match": { `data.${userId}.value`: 123 } }``. I see you used a "single" `\`` but you didn't get the rest of the interpolation correct. Also `$match` **first** always as this is not the same as `select * from d where this = "a"` and the "order" in an aggregation pipeline is important to performance. — Neil Lunn, May 15 '18 at 01:47

score 0 · Answer 1 · answered May 14 '18 at 22:26

0

   aggregate([
      {$project:{dataToarray:{$objectToArray: "$data"} }},     
      {$unwind:"$dataToarray"},
      {$match:{v:{$gt:10}}}
   ])

new in operator in 3.6 version

answered May 14 '18 at 22:26

Ahmed Kesha

Not what the question was asking. They wanted to use a variable to decide which key to search. Also, forcing projection in order to match on a value is a very bad idea in real world terms. – Neil Lunn May 15 '18 at 01:50

1 Answers1