Mongodb - Find in deeply nested array

Question

I am trying to find if type=conv is present in given rs , which is present in d --> ds --> rs --> type.

DOCUMENT

{
    "_id" : ObjectId("5ec25873bd796ff191e695b1"),
    "c_name" : "c1",
    "t_name" : "t1",
    "d" : [ 
        {
            "name" : "d1",
            "ds" : [ 
                {
                    "name" : "ds1",
                    "rs" : [ 
                        {
                            "type" : "conv"
                        }
                    ]
                }
            ]
        }, 
        {
            "name" : "d2",
            "ds" : [ 
                {
                    "name" : "ds2",
                    "rs" : []
                }
            ]
        }
    ]
}

QUERY:


filter = {
    "$and": [
        {"c_name": {'$eq': 'c1'}},
        {"t_name": {'$eq': 't1'}},
        {"d.name": {'$eq': 'd2'}},
        {"d.ds.name": {'$eq': 'ds2'}},
        {"d.ds.rs.type": {'$eq': 'conv'}}

    ]
}

OUTPUT

It is returning me document, i guess it is looking for presence of type = conv in full document, even though it is not present on ds2 ( part of d2), but present on ds1 ( part of d1).

Do we have simpler way to find if it exists or not, I would like to first find and then using array filters , we can update the specific element inside deeply nested array.

Could someone please suggest how should I approach this problem? ( if we have any solution without using aggregation )

@prasad_ - 1. projection can not be used on multi level nested array. 2. problem is mainly to find if an element type=conv exists for given d --> ds--> rs , it is finding it based on filter i am using , since type is present another d-->ds — nukul
– nukul, Commented May 18, 2020 at 10:45
"1. projection can not be used on multi level nested array." It can be used. — prasad_
– prasad_, Commented May 18, 2020 at 10:46
Can you pls provide me an example, of filter based on above, i can try to confirm to be aligned with you? — nukul
– nukul, Commented May 18, 2020 at 10:47

Puneet Singh · Accepted Answer · 2020-05-18 11:15:39Z

2

You need to use $elemMatch for these type of condition, And you can match strings without $eq operator

filter = {"$and": [
    {"c_name": "c1"},
    {"t_name": "t1"},
    { "d": { $elemMatch: { "name": "d2", "ds.name": "ds2" , "ds.rs.type": "conv"} } }
]}

With $elemMatch It will search only in the array where all condition will be true

answered May 18, 2020 at 11:15

Puneet Singh

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nukul · Accepted Answer · 2020-05-18 11:55:39Z

0

Thanks @puneet , i need to try above. However, i am using now this

filter_query = {
                "$and": [
                    {"c_name": {'$eq': 'c1'}},
                    {"t_name": {'$eq': 't1'}},
                    {
                        'd': {
                            '$elemMatch': {
                                'name': 'd2',
                                'ds': {
                                    '$elemMatch':
                                        {'name': 'ds2',
                                         'rs':
                                             {'$elemMatch':
                                                 {
                                                     "type": 'conv'}
                                             }
                                         }
                                }
                            }
                        }
                    }]}

This is also working !!

answered May 18, 2020 at 11:55

nukul

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3 Comments

Puneet Singh Over a year ago

Nice, you are checking the condition on every lever, Yes it depends on requirement :)

Puneet Singh Over a year ago

Happy to help :)

nukul Over a year ago

Thanks, indeed, array element is not unique, can be located across different array indices.

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