How to use PyMongo find() to search nested array attribute?

Question

Using PyMongo, how would one find/search for the documents where the nested array json object matches a given string.

Given the following 2 Product JSON documents in a MongoDB collection..

[{
    "_id" : ObjectId("5be1a1b2aa21bb3ceac339b0"),
    "id" : "1",
    "prod_attr" : [ 
        {
            "name" : "Branded X 1 Sneaker"
        },  
        {
            "hierarchy" : {
                "dept" : "10",
                "class" : "101",
                "subclass" : "1011"
            }
        }
    ]
},
{
    "_id" : ObjectId("7be1a1b2aa21bb3ceac339xx"),
    "id" : "2",
    "prod_attr" : [ 
        {
            "name" : "Branded Y 2 Sneaker"
        },  
        {
            "hierarchy" : {
                "dept" : "10",
                "class" : "101",
                "subclass" : "2022"
            }
        }
    ]
}
]

I would like to 1. return all documents where prod_att.hierarchy.subclass = "2022" 2. return all documents where prod_attr.name contains "Sneaker"

I appreciate the JSON could be structured differently, unfortunately that is not within my control to change.

vinsce · Accepted Answer · 2018-11-21 16:29:42Z

1. Return all documents where prod_attr.hierarchy.subclass = "2022"

Based on the Query an Array of Embedded Documents documentation of MongoDB you can use dot notation concatenating the name of the array field (prod_attr), with a dot (.) and the name of the field in the nested document (hierarchy.subclass):

collection.find({"prod_attr.hierarchy.subclass": "2022"})

2. Return all documents where prod_attr.name contains "Sneaker"

As before, you can use the dot notation to query a field of a nested element inside an array. To perform the "contains" query you have to use the $regex operator:

collection.find({"prod_attr.name": {"$regex": "Sneaker"}})

Another option is to use the MongoDB Aggregation framework:

collection.aggregate([
    {"$unwind": "$prod_attr"},
    {"$match": {"prod_attr.hierarchy.subclass": "2022"}}
])

the $unwind operator creates a new object for each object inside the prod_attr array, so you will have only nested documents and no array (check the documentation for details).
The next step is the $match operator that actually perform a query on the nested object.

This is a simple example but playing with the Aggregators Operators you have a lot of flexibility.

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How to use PyMongo find() to search nested array attribute?

1 Answer 1

1. Return all documents where prod_attr.hierarchy.subclass = "2022"

2. Return all documents where prod_attr.name contains "Sneaker"

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Collectives™ on Stack Overflow

1 Answer 1

1. Return all documents where prod_attr.hierarchy.subclass = "2022"

2. Return all documents where prod_attr.name contains "Sneaker"

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