Question 115309 in Mongodb Question posted in
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Mongodb – How to add a key in a mongo document on the basis of an existing key?

I have a document as follows:

{
    "_id": "1234",
    "created_at": 1678787680
}

I want to modify the document and add a new key updated_at which will be a datetime equivalent of the created_at UNIX timestamp.

{
    "_id": "1234",
    "created_at": 1678787680,
    "updated_at": "2023-03-14 15:39:18.767232"
}

Is there a way to perform this operation using updateMany?

Tags:

2

Answers


  1. 0

    Try this one:

    db.collection.aggregate([
   { $set: { updated_at: { $toDate: { $multiply: ["$created_at", 1000] } } } }
])
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  2. 0

    Use $toDate. You are better off storing dates as proper BSON date types (not as strings in your example).

    mongosh:

    db.mycollection.updateMany({}, [{'$set': {'updated_at': {'$toDate': {'$multiply': ['$created_at', 1000]}}}}])

    pymongo:

    db.mycollection.update_many({}, [{'$set': {'updated_at': {'$toDate': {'$multiply': ['$created_at', 1000]}}}}])

    full example:

    from pymongo import MongoClient

db = MongoClient()['mydatabase']


db.mycollection.insert_one({
    "_id": "1234",
    "created_at": 1678787680
})

db.mycollection.update_many({}, [{'$set': {'updated_at': {'$toDate': {'$multiply': ['$created_at', 1000]}}}}])
print(db.mycollection.find_one())

    prints:

    {'_id': '1234', 'created_at': 1678787680, 'updated_at': datetime.datetime(2023, 3, 14, 9, 54, 40)}
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