How to push an item into an array within an object within an array

Question

I have the following objects in MongoDB


 {
    "_id": {
        "$oid": "5f7274fe0fef0e383459e3ae"
    },
    "pwd": "$2a$10$AmA3lqNRdt315pgA3z9vNOkFMwisnu5zfcq0qVJzVSVm/0VYy3uQu",
    "daysfree": [{
        "date": {
            "$date": "2020-10-12T21:00:00.000Z"
        },
        "friends": ["pota", "toto", "loto"]
    }]
}

{
    "_id": {
        "$oid": "5f7b372d1c70e33c1cc41ec3"
    },
    "pwd": "$2a$10$H.2LGua3T2/wRhik792RtuPHJSzhRSJj5f6eV5bz/iGHywQ7Ylr2y",
    "daysfree": [{
        "date": {
            "$date": "2020-10-12T21:00:00.000Z"
        },
        "friends": ["hi", "hilo", "pota", "toto", "loto", "pota", "toto", "loto"]
    }]
}

And I want to update them such that for each document if the daysfree contains an object with the field date being set to "2020-10-12T21:00:00.00Z" then in the same exact object push to friends a new String.

Here are the queries I have tried that do half the job.


db.collection.update({
    "daysfree":{
        $elemMatch:{
            "date":{
                "$gte":ISODate("2020-10-12T00:00:00Z"),
                "$lt": ISODate("2020-10-13T00:00:00Z")
                }
            }
        }
    },{
        $push:{
            "daysfree.$.friends":"Josef"
        }
    }
);

The problem is that the query only updates the first document and not both of them.

Regards.

Wernfried Domscheit · Accepted Answer · 2020-10-21 19:40:34Z

1

update updates only the first matching document. Either use updateMany (which I prefer) or put optional parameter {multi: true}.

db.collection.update({
    "daysfree":{
        $elemMatch:{
            "date":{
                "$gte":ISODate("2020-10-12T00:00:00Z"),
                "$lt": ISODate("2020-10-13T00:00:00Z")
                }
            }
        }
    },
    { $push:{ "daysfree.$.friends":"Josef" } },
    { multi: true }
);

db.collection.updateMany({
    "daysfree":{
        $elemMatch:{
            "date":{
                "$gte":ISODate("2020-10-12T00:00:00Z"),
                "$lt": ISODate("2020-10-13T00:00:00Z")
                }
            }
        }
    },
    { $push:{ "daysfree.$.friends":"Josef" } },
);

edited Oct 21, 2020 at 19:40

answered Oct 21, 2020 at 19:35

Wernfried Domscheit

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