OperationalError: cursor “_django_curs_” does

Question

We have an online store web-app which is powered by django, postgresql and heroku.

For a specific campaign (you can think a campaign like a product to purchase), we have sold 10k+ copies successfully. Yet some of our users are encountered this error according to our Sentry reports. Common specification of these users is; none of them have address information before the purchase. Generally, users fill out address form right after registering. If they don't, they need to fill the form while purchasing the product and submit them together.

This is how the trace looks like:

OperationalError: cursor "_django_curs_140398688327424_146" does not exist

(66 additional frame(s) were not displayed)
...
  File "store/apps/store_main/templatetags/store_form_filters.py", line 31, in render_form
    return render_to_string('widgets/store_form_renderer.html', ctx)
  File "store/apps/store_main/templatetags/store_form_filters.py", line 20, in render_widget
    return render_to_string('widgets/store_widget_renderer.html', ctx)
  File "store/apps/store_main/widgets.py", line 40, in render
    attrs=attrs) + "<span class='js-select-support select-arrow'></span><div class='js-select-support select-arrow-space'><b></b></div>"

OperationalError: cursor "_django_curs_140398688327424_146" does not exist 

So another weird common thing, there are exception messages between sql queries before the failure. You can see it in the image below:

I'm adding it if they are somehow related. What may also be related is, the users who get this error are the users who tries to purchase the campaign right after a bulk mailing. So, extensive traffic might be the reason yet we are also not sure.

We asked Heroku about the problem since they are hosting the postgres, yet they do not have any clue either.

I know the formal reason of this error is trying to reach the cursor after a commit. Since it is destroyed after transaction, trying to reach it cause this error yet I don't see this in our scenario. We are not touching the cursor in any way. What am I missing? What may produce this error? How to prevent it? Any ideas would be appreciated.

Answer 1

If you're using django-pytest and have enabled the optimization --reuse-db and have made DB migrations between test runs you need to re-create the DB tables again.

pytest --create-db

Answer 2

The reason for your error might be that you added fields to a model and forgot to makemigrations and migrate.

Have a look at this answer: When in run test cases then I will get this error: psycopg2.OperationalError: cursor "_django_curs_140351416325888_23" does not exist