CODEWITHSUNDEEP
pythonmongodbpymongo
Swetank Poddar
Swetank Poddar

Reputation: 1291

Is it possible to rename "_id" to something else while aggregating in mongodb?

I have the following query

collection.aggregate([
        {"$match": {"timestamp": {"$gte": lastDateInUnix}} },
        {   "$group": {
                "_id": {
                    "$dateToString": {
                        "format": "%d-%m-%Y",
                        "date": {
                            "$toDate": {
                                "$multiply": [1000, "$timestamp"]
                            }
                        }
                    }
                },
                "totalMessages": {"$sum": 1 }
            }
        }
    ])

This returns something like this:

[
    {
        "_id": "05-01-2020",
        "totalMessages": 4
    }
]

As "_id" is a required field, is it possible to rename "_id" to say "dateOccurred"?

Upvotes: 1

Views: 73

Answers (1)

whoami - fakeFaceTrueSoul
whoami - fakeFaceTrueSoul

Reputation: 17915

You use a $project to do that, _id is a required field for documents existing in DB, but you transform the document or result the way you like using .aggregate() or .find() which are two ways you retrieve data from DB :

collection.aggregate([
    { "$match": { "timestamp": { "$gte": lastDateInUnix } } },
    {
        "$group": {
            "_id": {
                "$dateToString": {
                    "format": "%d-%m-%Y",
                    "date": {
                        "$toDate": {
                            "$multiply": [1000, "$timestamp"]
                        }
                    }
                }
            },
            "totalMessages": { "$sum": 1 }
        }
    },
    { $project: { dateOccurred: '$_id', totalMessages: 1, _id: 0 } }
])

Upvotes: 1

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