'filter object from array and select field

I've got a list of objects with name value pairs in them and I can't figure out how to retrieve a value from an array where name is a certain value.

For instance:

    {
            "ordernumber" : "192915",
            "orderparameters" : {
                    "list" : [
                            {
                                    "composite" : null,
                                    "name" : "CURRENCY_CODE",
                                    "value" : "NOK",
                                    "type" : "String"
                            },
                            {
                                    "composite" : null,
                                    "name" : "NEED_CUSTOMS_DOCUMENT",
                                    "value" : "True",
                                    "type" : "Boolean"
                            }
              ]}
    }

Now I need to find the value of the item with

"name": "NEED_CUSTOMS_DOCUMENT"

so in this case

"value": "True"

I can list all the values with

 db.orders.aggregate({ $match: { ordernumber:'1234' } }, { $project: { 'orderparameters.list.name': 1 } }).pretty()

But then how to retrieve the value field from the index with that name?

The index could be different on every document so I cant simply query "orderparameters.list.1.value"

mongodbmongodb-queryaggregation-framework


Solution 1:[1]

There is an operator especially made for this

$elemMatch

The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.

db.orders.aggregate({ $match: { 'orderparameters.list': { $elemMatch: { name: "NEED_CUSTOMS_DOCUMENT", value: "True" } } } })

db.orders.find({ 'orderparameters.list': { $elemMatch: { name: "NEED_CUSTOMS_DOCUMENT", value: "True" } } })

Sources

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Source: Stack Overflow

Solution Source
Solution 1 GCloony

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