Ticket: Migration, Having a problem with pymongo

MongoDB University M220P: MongoDB for Python Developers
#1

Hi,
Having a problem with pymongo
bson.errors.InvalidDocument: Cannot encode object: {‘lastupdated’, datetime.datetime(2015, 8, 26, 0, 3, 50)}

How did you people solve this? any ideas?

#2

Welcome to the community @Haki_Dere,

This looks related to the Ticket: Migration exercise and the updates for movie_last_updated_migration.py, can you confirm if my understanding is correct?

If this is correct, have you edited this file and specifically updated this line:

predicate = {"some_field": {"$some_operator": "some_expression"}}

In terms of the update necessary to the code, it will involve the field “lastupdated” and two operators ("$exists" and “$type”).

Can you share the code you have updated for those two lines as both of these need to be updated in the file movie_last_updated_migration.py for that specific exercise?

Hope this helps and please let me know if I’ve mistaken your question and it relates to a different lesson/exercise.

Kindest regards,
Eoin

1 Like
#3

Hey Eoin,
Thanks for your response, very kind of you!.
Here is the code:

pymongo version: pymongo==3.7.2

predicate = {"lastupdated": {"$type": "string"}}
projection = {"lastupdated": 1}

cursor = mflix.movies.find(predicate, projection)

# this will transform the "lastupdated" field to an ISODate() from a string
movies_to_migrate = []
for doc in cursor:
    doc_id = doc.get('_id')
    lastupdated = doc.get('lastupdated', None)
    movies_to_migrate.append(
        {
            "doc_id": ObjectId(doc_id),
            "lastupdated": parser.parse(lastupdated)
        }
    )

print(f"{len(movies_to_migrate)} documents to migrate")

try:

    # build the UpdateOne so it updates the "lastupdated" field to contain
    # the new ISODate() type
    bulk_updates = [UpdateOne(
        {"_id": movie.get("doc_id")},
        {"$set": {"lastupdated", movie.get("lastupdated")}}
    ) for movie in movies_to_migrate]

    # here's where the bulk operation is sent to MongoDB
    bulk_results = mflix.movies.bulk_write(bulk_updates)
    print(f"{bulk_results.modified_count} documents updated")

except InvalidOperation:
    print("no updates necessary")
except Exception as e:
    raise e
#4

Hi @Haki_Dere

You should also add “$exists”: True to your predicate, the rest of your code looks correct.

Kindest regards,
Eoin