Optimization error: lookup was already seen with a different queryset. You may need to adjust the ordering of your lookups

[cpontvieux-systra]

I’m having this error (from django.db) with my actual schema for some queries, but only if the DjangoOptimizerExtension is in place.

I narrowed down my project to a minimum reproducible scenario.

My exact error message is:

"steps" lookup was already seen with a different queryset. You may need to adjust the ordering of your lookups

How to reproduce it ?

• Get the mini project archive: bug-prefetch-strawberry-django-plus.tar.gz
• Extract it to a folder of your choice
• Install dependencies with poetry and enter shell
• Prepare database (sqlite) and run a dev server:

./manage.py migrate
./manage.py runscript app.import
./manage.py runserver_plus

• Open your browser to /graphql/ to open GraphiQL and try this query:

query {
  allProjects {
    id
    name
    isPublished
    workflowTemplates {
      id
      name
      sequence
      steps {
        sequence
        type
        label
        days0
        daysX
      }
    }
  }
}

• Constat the error message about prefetch clashing.
• Open app/schema.py file and change with_optim = False ⇒ the bug disappear.

Site nodes

I know the optimizer is not a silver bullet and dynamically prefetching is hard. But I expect the query to complete, even if not correctly optimized.

• What I can do to my code to help the optimizer?
• How can I forsee when (and why) I need to help the optimizer (if it’s possible)?

If any information is missing, please ask. I also can be contacted directly by email at [email protected].