Converting aggregation results to umongo objects

I’m using umongo to gather documents using mongos aggregation framework:

MyDocumentClass.collection.aggregate([
            {'$match': {
                'field1': value1,
                'field2': value2
            }},
            # more pipes
        ])

The resulting documents are plain dictionaries. It wouldn’t be that bad since i want to convert them to json for serving over an api anyway, but i loose umongos nice integration for dump() that way and i would have to convert objectIDs, Dates etc myself.

My current solution is iterating over the results and converting them into my desired umongo Class

raw_docs = await above_future.to_list(None)
docs = [MyDocumentClass.build_from_mongo(docs) for docs in raw_docs]

Is there a better way to do this or what is your recommended solution for converting aggregate results to umongo Document objects (i can totally see why you wouldn’t do this automatically since aggregation results don’t have to be anyway structured like modeled Document classes)?

[touilleMan]

My Problem now is that i have to define a Document subclass if i want to use umongos abstraction and another Schema subclass, thats nearly the same, for using aggregation. Resulting problems when doing this are inconsistences f.e. my ID field is called id on umongo and _id on marshmallow schemas.

I don’t get the trouble: given the result of your aggregation is the document itself why your first solution doesn’t work anymore ?

raw_docs = await above_future.to_list(None)
docs = [MyDocumentClass.build_from_mongo(docs) for docs in raw_docs]

Beside, I think we can make thing more elegant for your needs by adding a bind_as attribute to the aggregate function in order to do the construction of the Documents inside the returned cursor:

@instance.register
class AggregatedObj(EmbeddedDocument):
    field1 = fields.StrField()
    field2 = ...

results = MyDocumentClass.collection.aggregate([
            {'$match': {
                'field1': value1,
                'field2': value2
            }},
            # more pipes
        ], bind_as=AggregatedObj)

(await results.to_list(None))[0]
# <object EmbeddedDocument __main__.AggregatedObj({'field1': ...})>

What do you think ?

[lafrech]

Closing this as

the result of the aggregation can be very different to the orginal document