Pymongo update_one issue with nested fields

Working with Data Drivers
,
1

I have a document with nested objects in the following format:

{
    ...
    search_preferences: {
        ...
        bad_job_titles: []
    }
}

Now, we update the nested field using the update_one method and $set operator.

db[collection].update_one({"id": id}, {"$set": {"search_preferences.bad_job_titles": ["xyz"]}})

It works mostly, but sometimes in production we are seeing documents where instead of updating the bad_job_titles, there’s a separate field in the document as “search_preferences.bad_job_titles” in the follow format:

{
    ...
    search_preferences: {
        ...
        bad_job_titles: []
    },
    search_preferences.bad_job_titles: ["xyz"]
}

I have been scratching my head, but not sure what’s happening here, and why it would happen only to some documents.

2

In principal running the same code with the same data leads to the same results. I do not see any reason why $set would start to ignore the dot notation.

What I suspect is one of the following scenario:

1 - someone used Compass to create the field with the dot
2 - someone used $setField to create the field with the dot