Mongoengine如何在集合中的EmbeddedDocumentListField中检索过滤的子文档

Question

I have a document model as follows:

class MyDocumentModel(DynamicDocument):
    subdocuments = EmbeddedDocumentListField(MySubdocumentModel)

class MySubdocumentModel(EmbeddedDocument):
    some_field = StringField()

What I want to be able to do is get a list of all MySubdocumentModel embedded documents contained in MyDocumentModel documents in the entire collection by filtering subdocuments on some_field . Does anyone know if this is possible/how to accomplish this in mongoengine ? My research up to this point has not yielded anything that has worked.

Things I've tried:

MyDocumentModel.objects(subdocuments__some_field="my_field_value")
MyDocumentModel.objects(subdocuments__match={"some_field": "my_field_value"})

Any advice would be greatly appreciated.

Answer 1

With some additional searching and experimenting, I found you can do this:

subdocs = MyDocumentModel._get_collection().aggregate([
            {"$unwind": "$subdocuments"},
            {"$match": {'subdocuments.some_field':'my_field_value'}}
          ])

I hope this helps others who need to do something similar.