Standardize delete_cached_value API on model Fields

[Taylor H]

I created a custom Django model field that is expensive to calculate and I store a cached value on the model. I am not able to clear the cache when some uses the refresh_from_db() method though, since there is no standard API to hook into it. It appears that there is a custom behavior for ForeignKey that calls the delete_cached_value function, if it detects it's a ForeignKey

​https://github.com/django/django/blob/master/django/db/models/base.py#L569

It would be great to allow any custom Field to implement delete_cached_value and have it called inside refresh_from_db. What are your thoughts? I would be happy to submit a PR if this seems reasonable

[Tim Graham]

Could you detail a bit more about what your use case looks like? It's not clear to me what changes in Django are needed to solve it.

[Tim Graham]

Comment from Carlton Gibson: "My initial thought here is just to override refresh_from_db(). I appreciate that’s slightly more involved than just using the field on the model, but it does mean no extra API in Django. "

[Carlton Gibson]

Hi taylor, I'm going to close this as-is. If you can follow-up with answers to the questions we may re-open. Thanks.