DjangoConnectionField discards select_related

[crucialfelix]

graphene-django==1.3

https://github.com/graphql-python/graphene-django/blob/master/graphene_django/fields.py#L59

When you do this:

# DjangoFilterConnection

    @classmethod
    def merge_querysets(cls, default_queryset, queryset):
        return default_queryset & queryset

you discard any select_related or prefetch_related or annotate that might have been applied to the query set.

When we write a def resolve_things(self,... method and return a customized QuerySet it is then merged into the default_queryset and this discards everything (I think) except the filtering.

queryset = Deals.objects.select_related('client')

> /usr/local/lib/python2.7/dist-packages/graphene_django/fields.py(58)merge_querysets()
     56             return self.model._default_manager
     57
---> 58     @classmethod
     59     def merge_querysets(cls, default_queryset, queryset):
     60         return default_queryset & queryset

ipdb> queryset[0].client
[0.051] SELECT "clients_deal"."id",
       "clients_deal"."client_id",
       "clients_deal"."agent_id",
       "clients_deal"."type",
       "clients_deal"."open",
       "clients_deal"."stage",
       "clients_deal"."created_on",
       "clients_deal"."modified_on",
       "clients_deal"."client_last_active_on",
       "clients_client"."id",
       "clients_client"."contact_id",
       "clients_client"."email",
       "clients_client"."fname",
       "clients_client"."lname",
       "clients_client"."phone",
       "clients_client"."work",
       "clients_client"."verified",
       "clients_client"."suggested_listings",
       "clients_client"."referral_source_id",
       "clients_client"."created_on",
       "clients_client"."modified_on",
       "clients_client"."created_by_id"
FROM "clients_deal"
INNER JOIN "clients_client" ON ("clients_deal"."client_id" = "clients_client"."id")
WHERE ("clients_deal"."agent_id" = 769
       AND "clients_deal"."open" = true
       AND "clients_deal"."agent_id" = 769)
ORDER BY "clients_deal"."client_last_active_on" DESC
LIMIT 1

# no extra query required
<Client: BOb Hop>

# here is after merging using &
ipdb> merged = default_queryset & queryset
ipdb> merged[0].client
[0.006] SELECT "clients_deal"."id",
       "clients_deal"."client_id",
       "clients_deal"."agent_id",
       "clients_deal"."type",
       "clients_deal"."open",
       "clients_deal"."stage",
       "clients_deal"."created_on",
       "clients_deal"."modified_on",
       "clients_deal"."client_last_active_on"
FROM "clients_deal"
WHERE ("clients_deal"."agent_id" = 769
       AND "clients_deal"."open" = true
       AND "clients_deal"."agent_id" = 769)
ORDER BY "clients_deal"."client_last_active_on" DESC
LIMIT 1

[0.006] SELECT "clients_client"."id",
       "clients_client"."contact_id",
       "clients_client"."email",
       "clients_client"."fname",
       "clients_client"."lname",
       "clients_client"."phone",
       "clients_client"."work",
       "clients_client"."verified",
       "clients_client"."suggested_listings",
       "clients_client"."referral_source_id",
       "clients_client"."created_on",
       "clients_client"."modified_on",
       "clients_client"."created_by_id"
FROM "clients_client"
WHERE "clients_client"."id" = 188672

I'm not quite sure what the purpose of merging it with the default query is.

[hassa]

+1 Why does default_queryset even come into play here? Shouldn't it just be the iterable from the resolver:

https://github.com/graphql-python/graphene-django/blob/master/graphene_django/fields.py#L86

or the default_queryset if none is specified?

This also affects DjangoFilterConnectionField (may need a new ticket) where instead of the queryset from the resolver being filtered, the default from the manager is being filtered.

https://github.com/graphql-python/graphene-django/blob/master/graphene_django/filter/fields.py#L76

which is very wrong unless I am totally missing something.

The resolved iterable may already be filtered based on context (for example I only want to show you rows you are allowed to see), but then the filter ends up just filtering the default - showing rows the user may not be allowed to see, and merging those...

[crucialfelix]

I think it's a bug and we should do a PR and fix it. At the moment I am using my own DjangoFilterConnectionField subclass that patches the problem.

[camd]

Any tips on working around this? @crucialfelix would you be up for sharing a bit of your code? :)

[crucialfelix]

from graphene_django.fields import DjangoConnectionField as _DjangoConnectionField

class DjangoConnectionField(_DjangoConnectionField):

    """
    Temporary fix for select_related issue
    """

    @classmethod
    def merge_querysets(cls, default_queryset, queryset):
        """
        This discarded all select_related and prefetch_related:
        # return default_queryset & queryset
        """
        return queryset

[camd]

Thanks @crucialfelix. I ended up doing something similar to this, borrowed some ideas from others in threads similar to this and created my own implementation of applying select_related and prefetch_related where I needed it.

In case it helps someone else, here's my gist: https://gist.github.com/camd/cae123923ba8ce2442ebd6e1be34377e

[crucialfelix]

This bug also affects all auto-generated resolvers for ManyToMany fields

Given:

class Apt(models.Model)
    neighborhoods = models.ManyToManyField("Neighborhood")

class Apt(DjangoObjectType):

    class Meta:
        model = models.Apt

No custom fields or resolve_neighborhoods defined.

query {
  apt(pk: 1) {
    neighborhoods {
      edges { node { id name }}
  }
}

The default resolver returns the apt.neighborhoods.all() but then tries to merge it into Apt.objects.all()

    return Promise.resolve(next(*a, **b))
  File "/usr/local/lib/python2.7/dist-packages/graphene_django/fields.py", line 93, in connection_resolver
    iterable = cls.merge_querysets(default_queryset, iterable)
  File "/usr/local/lib/python2.7/dist-packages/graphene_django/fields.py", line 60, in merge_querysets
    return default_queryset & queryset
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 307, in __and__
    combined.query.combine(other.query, sql.AND)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py", line 513, in combine
    "Cannot combine queries on two different base models."
AssertionError: Cannot combine queries on two different base models.