Re: [Django] #29911: Standardize delete_cached_value API on model Fields (was: Standardize `delete_cached_value API` on model Fields)

[Django]

#29911: Standardize delete_cached_value API on model Fields
-+-
 Reporter:  Taylor Hakes |Owner:  nobody
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  2.1
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

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Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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Re: [Django] #29911: Standardize `delete_cached_value API` on model Fields (was: Standardize delete_cached_value API on model Fields)

[Django]

#29911: Standardize `delete_cached_value API` on model Fields
-+-
 Reporter:  Taylor Hakes |Owner:  nobody
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  2.1
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Description changed by Taylor Hakes:

Old description:

> 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

New description:

 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

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Ticket URL: 
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