Prefetch_related in root resolver not preserved in children resolvers

It seems that prefetch_related is not preserved in children resolvers. (select_related is no problem).

Example

This example is a simplified version of the code I am working with.

Models

class Family(models.Model):
    name = models.CharField(max_length=255)


class Person(models.Model):
    name = models.CharField(max_length=256)
    family = models.ForeignKey('Family', related_name='members')

Nodes

class PersonNode(DjangoObjectType):
    class Meta:
        model = Person
        interfaces = (graphene.relay.Node,)


class FamilyNode(DjangoObjectType):
    members = graphene.ConnectionField(PersonNode)

    class Meta:
        model = Family
        interfaces = (graphene.relay.Node,)

“Endpoint”

class Query(graphene.ObjectType):
    families = graphene.ConnectionField(Family)

    def resolve_families(self, args, context, info):
        qs = Family.objects.prefetch_related('members')
        return qs

Query

{
  families {
    edges {
      node {
        members {
          edges {
            node {
              name
            }
          }
        }
      }
    }
  }
}

Problem

The family members were prefetched in the root resolver but that is definitely not used in children resolvers as a db query is made for person data each time a family is resolved.

Question

Does anyone have an idea how to get prefetch_related used in children resolvers?

[jkimbo]

@japrogramer @hgylfason @jonbesga I think I’ve found the issue that is meaning that prefetch_related is not preserved. It’s a bug and this PR should fix it: https://github.com/graphql-python/graphene-django/pull/693

[jkimbo]

And thanks @japrogramer for helping figure out the problem. Made fixing it very simple 😄