Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-06-17 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by Marco Glauser):

 We ran into the same issue. We tried to switch the responsible user of a
 task depending on some simple business logic that could be evaluated by
 the GeneratedField.

 The ForeignObject approach is working for us.

 For anyone stumbling on this discussion later on, we observed a caching
 issue with ForeignObject. The cache of the field doesn't get refreshed
 when `refresh_from_db` gets called.
 We had to explicitly override `refresh_from_db` on the Task model

 {{{
 def refresh_from_db(self, using=None, fields=None):
 super(Task, self).refresh_from_db(using=using, fields=fields)
 responsible_user_field = self._meta.get_field("responsible_user")
 if responsible_user_field.is_cached(self):
responsible_user_field.delete_cached_value(self)
 }}}
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-03 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by fero):

 Replying to [comment:7 Simon Charette]:
 > You don't need any `GeneratedField` subclass to achieve what you're
 after, simply use `ForeignObject` which is the accessor base of
 `ForeignKey`.

 Thank you very much for the snippet Simon, I am going to try for sure!

 > I also believe there is no reason to add this feature in core as with
 these two primitives it should be trivial to implement a
 `ForeignGeneratedField(ForeignObject)` that does exactly what you're after
 in a third-party application for the rare use case this is useful.

 I am not sure this is a rare case, but you could be right.
 If not, it would be useful to have it imho because needs internal
 knowledge.

 Let's try and see if I am able to build a 3rd party app. Thanks
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-03 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by Simon Charette):

 You don't need any `GeneratedField` subclass to achieve what you're after,
 simply use `ForeignObject` which is the accessor base of `ForeignKey`.

 {{{#!python
 from django.db.models.fields.related_fields import ForeignObject

 class Event(models.Model):
 last_updated_by_id = models.GeneratedField(
 expression=Greatest("created_by", "confirmed_by", "canceled_by"),
 output_field=models.BigIntegerField(),
 db_index=True,
 db_persist=True,
 )
 last_updated_by = ForeignObject(
 User,
 models.SET_NULL,
 from_fields=["last_updated_by_id"],
 to_fields=["id"],
 related_name="last_updated_events_set",
 null=True,
 )
 }}}

 I also believe there is no reason to add this feature in core as with
 these two primitives it should be trivial to implement a
 `ForeignGeneratedField(ForeignObject)` that does exactly what you're after
 in a third-party application for the rare use case this is useful.
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-03 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by fero):

 Hello Sarah,
 thanks for the answer

 Replying to [comment:4 Sarah Boyce]:
 > Hi Perrine,

 Perrine?!? Sorry...I think you are answering me, and not Perrine. I hope
 to be right.

 > this ticket should only be re-opened if you do as Mariusz requested and
 provide a valid column DDL definition that you believe is not currently
 supported.

 I have opened the issue without a DDL because the matter is just a way on
 how Django give an accessor to ForeignKey attributes, mainly very useful
 lookup. And this can be done (at least in PostgreSQL) even without
 constraints. So no DDL really required for this feature.

 > I believe this will not be possible as
 [https://www.postgresql.org/docs/current/ddl-generated-columns.html the
 linked documentation states] and Mariusz mentioned, `GeneratedFields`
 cannot reference anything other than the current row in **any way** and
 being a `ForeignKey` is a reference to an external model.

 Yes, the GeneratedField can reference only info of its own row. I have had
 the problem when I wanted to created a generated field with a CASE WHEN
 and apply a Now(), aka CURRENT_TIMESTAMP as a default value. This cannot
 be done.

 But in this case the ForeignKey is just and ID and it is computed from
 data of its own row. It is really the same as a BigIntegerField (or a
 CharField if you use id like ssn), but it gives you a quicker way to
 access to the related model.

 So, I really appreciate your answer, but my humble opinion disagrees with
 the position that implementing this feature would imply that
 GeneratedField relies in external data.


 > Thank you for the sample project and I can see what you're trying to do.
 As what you're suggesting would be a new feature to Django, the
 recommended path forward is to first propose and discuss the idea with the
 community and gain consensus that this would be a desirable addition to
 Django. To do that, please consider starting a new conversation on the
 [https://forum.djangoproject.com/c/internals/5 Django Forum], where you'll
 reach a wider audience and likely get extra feedback.
 >
 > I'll close this ticket, but if there is a community agreement for the
 feature request, you are welcome to create a ticket for the new feature
 and point to the forum topic. For more details, please see
 [https://docs.djangoproject.com/en/stable/internals/contributing/bugs-and-
 features/#requesting-features the documented guidelines for requesting
 features].
 >

 I leave the ticket closed, but I have answered here to return you with a
 feedback, and to link the ticket in the forum where I will go.

 Thank you very much!
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-02 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Natalia Bidart):

 * type:  Bug => New feature

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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-02 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  invalid
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Sarah Boyce):

 * resolution:   => invalid
 * status:  new => closed

Comment:

 Hi Perrine, this ticket should only be re-opened if you do as Mariusz
 requested and provide a valid column DDL definition that you believe is
 not currently supported.
 I believe this will not be possible as
 [https://www.postgresql.org/docs/current/ddl-generated-columns.html the
 linked documentation states] and Mariusz mentioned, `GeneratedFields`
 cannot reference anything other than the current row in **any way** and
 being a `ForeignKey` is a reference to an external model.

 Thank you for the sample project and I can see what you're trying to do.
 As what you're suggesting would be a new feature to Django, the
 recommended path forward is to first propose and discuss the idea with the
 community and gain consensus that this would be a desirable addition to
 Django. To do that, please consider starting a new conversation on the
 [https://forum.djangoproject.com/c/internals/5 Django Forum], where you'll
 reach a wider audience and likely get extra feedback.

 I'll close this ticket, but if there is a community agreement for the
 feature request, you are welcome to create a ticket for the new feature
 and point to the forum topic. For more details, please see
 [https://docs.djangoproject.com/en/stable/internals/contributing/bugs-and-
 features/#requesting-features the documented guidelines for requesting
 features].
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-02 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  5.0
  (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
-+-
Changes (by fero):

 * resolution:  needsinfo =>
 * status:  closed => new

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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-04-02 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  needsinfo
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Comment (by fero):

 Hello, I think I have developed something that would do for this bug. With
 RelatedField on a GeneratedField it is possible to use all wonderful
 Django ORM lookup features.

 https://github.com/feroda/play-django-generatedfk

 Now my implementation requires a separate field (I have called
 NoopForeignKey https://github.com/feroda/play-django-
 generatedfk/blob/main/noopfk/fields.py), in addition to the
 GeneratedField, but I think it is not too much work to integrate the
 feature in a dedicated field to be used as `output_field` (maybe:
 models.GeneratedForeignKey?) and I am almost confident that it could be a
 benefit also for referencing F() foreign key fields that should not
 provide only the value of the foreign key, but also the RelatedManager
 too.

 What do you think about it?
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Re: [Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-03-04 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
 Reporter:  Perrine L.   |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  5.0
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  needsinfo
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Mariusz Felisiak):

 * resolution:   => needsinfo
 * status:  new => closed

Comment:

 Related fields were never intended to be used as `output_field`s.
 Moreover, as far as I'm aware, `GeneratedField`s cannot refer fields from
 external models, so I'm not exactly sure what kind of column you want to
 add. Please add a sample project that reproduces your issue, and provide a
 valid column DDL definition that you believe is not currently supported.
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[Django] #35269: GeneratedFields can't be defined on RelatedFields

2024-03-04 Thread Django 
#35269: GeneratedFields can't be defined on RelatedFields
-+-
   Reporter:  Perrine|  Owner:  nobody
  L. |
   Type:  Bug| Status:  new
  Component:  Database   |Version:  5.0
  layer (models, ORM)|
   Severity:  Normal |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |
Needs documentation:  0  |Needs tests:  0
Patch needs improvement:  0  |  Easy pickings:  0
  UI/UX:  0  |
-+-
 It is not possible to define a GeneratedField with a ForeignKey or a
 ManyToManyField as an output_field.
 When those RelatedFields are defined as output_field, an error is raised

 ```AttributeError: 'ForeignKey' object has no attribute 'opts'``` line
 190, in _check_relation_model_exists or line 494, in related_query_name
 (cf.
 
https://github.com/django/django/blob/3d4fe39bac082b835a2d82b717b6ae88ea70ea15/django/db/models/fields/related.py)

 At least with Postgres as a backend, there doesn't seem to be any
 technical impossibility to make a GeneratedField on a ForeignKey or
 ManyToMany fields : https://www.postgresql.org/docs/current/ddl-generated-
 columns.html
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