Query efficiency and performance - Retrieving only the queried fields from the database by implementing deafult resolvers for both ReferenceField & CachedReferenceField.

Author: Arun S Kumar

graphene_mongo/converter.py

@@ -6,7 +6,7 @@
 from mongoengine.base import get_document
 
 from . import advanced_types
-from .utils import import_single_dispatch, get_field_description, get_query_fields
+from .utils import import_single_dispatch, get_field_description, get_query_fields, camel_to_snake
 
 singledispatch = import_single_dispatch()
 
@@ -172,13 +172,13 @@ def convert_field_to_dynamic(field, registry=None):
 
     def reference_resolver(root, *args, **kwargs):
         document = getattr(root, field.name or field.db_name)
-        only_fields = get_query_fields(args[0]).keys()
-        return field.document_type.objects().only(*only_fields).get(pk=document.id)
+        only_fields = [camel_to_snake(i) for i in get_query_fields(args[0]).keys()]
+        return field.document_type.objects().no_dereference().only(*only_fields).get(pk=document.id)
 
     def cached_reference_resolver(root, *args, **kwargs):
-        document = getattr(root, field.name or field.db_name)
-        only_fields = get_query_fields(args[0]).keys()
-        return field.document_type.objects().only(*only_fields).get(pk=document)
+        only_fields = [camel_to_snake(i) for i in get_query_fields(args[0]).keys()]
+        return field.document_type.objects().no_dereference().only(*only_fields).get(
+            pk=getattr(root, field.name or field.db_name))
 
     def dynamic_type():
         _type = registry.get_type_for_model(model)
@@ -201,10 +201,9 @@ def convert_lazy_field_to_dynamic(field, registry=None):
     model = field.document_type
 
     def lazy_resolver(root, *args, **kwargs):
-        if getattr(root, field.name or field.db_name):
-            only_fields = get_query_fields(args[0]).keys()
-            document = getattr(root, field.name or field.db_name)
-            return document.document_type.objects().only(*only_fields).get(pk=document.pk)
+        document = getattr(root, field.name or field.db_name)
+        only_fields = [camel_to_snake(i) for i in get_query_fields(args[0]).keys()]
+        return document.document_type.objects().no_dereference().only(*only_fields).get(pk=document.pk)
 
     def dynamic_type():
         _type = registry.get_type_for_model(model)

graphene_mongo/fields.py

@@ -199,7 +199,7 @@ def get_queryset(self, model, info, only_fields=list(), **args):
             else:
                 args.update(queryset_or_filters)
 
-        return model.objects(**args).order_by(self.order_by)
+        return model.objects(**args).only(*only_fields).order_by(self.order_by)
 
     def default_resolver(self, _root, info, only_fields=list(), **args):
         args = args or {}