PyMongo: Using $push to update an existing document with a reference to another document

Question

I have a teams collection and a players collection. I am trying to insert documents into the teams* collection from the **players collection using $push.

Here are the data models for both:

Teams:

        {
            "team_id": 1,
            "team_name": team_name,
            "general_manager": general_manager,
            "players": [

            ]
        }

Players:

        {
            "_id": "5c076550c779ce4fa2d4c9fd"
            "first_name": first_name,
            "last_name": last_name,
        }

Here is the code I'm using:

        player = players.find_one({ "$and": [
        {"first_name": first_name},
        {"last_name": last_name}] })


    teams.update(
        {"team_name": team_name},
        {"$push":
             {"players": {
                 "$ref": "players",
                 "$id": player["_id"],
                 "$db": db
             }}})

When I execute this, I get the following error message:

pymongo.errors.WriteError: Found $id field without a $ref before it, which is invalid.

What am I doing wrong? Thanks in advance!

Answer 1

I simplified your queries a bit. Try below (explanation in comments)

//Locate the player record
player = players.find_one({"first_name": first_name,"last_name": last_name})

//push this into the "players" array of the team
teams.update_one({"team_name": team_name},
    {"$push":  {"players":  player } } 
)

I used update_one instead of update, as I assume you only need to update one document in the teams collection.