I want to add a record to the collection if the key doesn't already exist. I understand [MongoDB][1] offers the upsertfor this so I did a
db.collection.update({"_id":"key1"},{"_id":"key1"},True)
This seems to work.
However in the Pymongo documentation it says that update is deprecated and use to update_one().
But:
db.collection.update_one({"_id":"key1"},{"_id":"key1"},True)
Gives:
raise ValueError('update only works with $ operators')
ValueError: update only works with $ operators
I don't really understand why update_one is different and why I need to use a $ operator. Can anyone help?
2 Answers
This is because you didn't specify any update operator.
For example to $set the id value use:
db.collection.update_one({"_id":"key1"}, {"$set": {"id":"key1"}}, upsert=True)
Note that in the Mongo shell, this will simply replace the document with the new document.
Use replace_one() instead of update_one(). the 3rd parameter of replace_one() is upsert, too.
db.collection.replace_one({"_id": "key1"}, {"_id": "key1"}, True)
My personal opinion is this implementation of update_one() is inconsistent with the behaviour of MongoDB client. The upsert option in update_one() is actually meaningless. But the developers of pyMongo may just want to use this to distinguish update_one() and replace_one().
