Collation, Hint, and Comment Ignored During QuerySet Update/Delete/Aggregate

[Winedays]

Hi everyone, I encountered an issue when using collation for index creation, and then querying with that collation.

I discovered this problem when using collation for index creation and performing queries. I found that when collation is set on a QuerySet, and operations like update, delete, or aggregate are performed, MongoEngine does not propagate the collation options to the corresponding PyMongo functions. As a result, the index is not used, leading to collection scans (COLLSCAN).

Initially, I discovered this issue with collation, but further inspection of the source code revealed that both hint and comment settings also suffer from the same problem.

Steps to Reproduce
Create a Document with Index Using Collation:

class MyDoc(Document):
    name = StringField()
    
    meta = {
        'indexes': [
            {'fields': ['name'], 'collation': {'locale': 'en', 'strength': 2}}
        ]
    }

Perform a Query with Collation, Then Attempt to Update or Delete Documents:

# Query with collation specified
qs = MyDoc.objects(name='alice').collation(locale='en', strength=2)

# The following operations do not pass collation, hint, or comment to PyMongo
qs.update(set__name='Alice')  # Update
qs.delete()                   # Delete
qs.aggregate([{'$group': {'_id': '$name'}}])  # Aggregate

Observe the Result in MongoDB: MongoDB performs a collection scan (COLLSCAN) instead of utilizing the index due to collation.

I noticed that hint and comment seem to be suffering from a similar problem, they are not being delivered correctly. While I haven't specifically tested it, the source code suggest these are possible.

Environment

• MongoEngine Version: 0.28.2
• PyMongo Version: 4.8.0
• Python Version: 3.12