Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  closed
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution:  wontfix|   Keywords:
   Triage Stage:  Design |  Has patch:  0
  decision needed|Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
  UI/UX:  0  |
-+-
Changes (by mtredinnick):

 * status:  new => closed
 * ui_ux:   => 0
 * resolution:   => wontfix


Comment:

 I'm with Alex for most of the same reasons. Retrofitting the database
 level behaviour of a parent class feels a bit fragile. Model inheritance
 differs from Python class inheritance in a few ways and overriding is one
 of them. A field validator is probably one solution here.

 The reuse argument doesn't convince me a lot, either. If the field is
 genuinely intended to be reused as unique, it should be marked as such.
 It's not really subclassing when it's both unique and non-unique in
 different situations -- it's attempting to reuse something of the same
 name in different context, not using "is-a" relationships.

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage:  Design |  Has patch:  0
  decision needed|Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Comment (by julien):

 That's fair enough. Thanks for your feedback. I'm not too precious about
 this and I won't mind if it gets wontfixed.

 Just for the sake of argumentation, the case could also be made that the
 framework could allow the overriding of certain field properties at the
 `Model` level, in the same way as, like noted above, a form field's
 `widget` property can be overridden at the `ModelForm` level. Purely as a
 convenience.

 Also, I often see many of the constraints linked to model inheritance,
 like to one pointed out by this ticket, quite unfortunate as they
 drastically limit the possibilities of making apps reusable. In my case,
 it's a shame that the abstract class `A` cannot be reused so easily in any
 context, where certain of its fields may or may not be unique. One
 approach would be to have the app ship some mixins `A1` and `A2`, both
 defining a `blah` field but the former setting `unique=False` and the
 latter `unique=True`. But again, this would mean the app would have to
 anticipate every use case it might be used in, which again goes against
 the principles of reusability.

 Anyway, for me this would be a nice-to-have feature rather than something
 essential. Maybe this is also highlighting some bigger issues with
 Django's handling of model inheritance and therefore should be part of a
 broader discussion.

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage:  Design |  Has patch:  0
  decision needed|Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-
Changes (by Alex):

 * stage:  Unreviewed => Design decision needed


Comment:

 I'm -1 on this feature, it moves a field level option to the model level,
 which is wrong, also if the issue is inheritance solving just one special
 case is the complete wrong way to do this.  Finally, a strong argument can
 be made that it's completely inappropriate to allow changing the field on
 subclasses (even in the abstract case, it obviously is in the MTI case).
 Marking as DDN for now, but I'm inclined to wontfix it.

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Comment (by julien):

 Just a note. The new feature suggested here would be in the same spirit as
 `ModelForm.Meta.widgets` [1], which allows to override the widgets for
 given individual form fields instead of having to redefine the entire
 fields themselves. So, even if it were possible to override an entire
 `Model` field, I think it would still be nice to be able to override
 certain field properties, like `unique` for example.

 I understand that we don't want to overload the `Meta` options, but
 hopefully it would make sense in this case. I don't know enough about the
 ORM to predict if there could be bad side effects so I'm leaving it up to
 the ORM experts to decide ;-)

 [1] http://docs.djangoproject.com/en/dev/topics/forms/modelforms
 /#overriding-the-default-field-types-or-widgets

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-
Changes (by jonash):

 * cc: jonas-django@… (added)


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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Comment (by jezdez):

 Uh, seems like a bug to me, but the ORM isn't my strong field.. waiting
 for someone capable to review it.

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Comment (by julien):

 Replying to [comment:3 jezdez]:
 > Wouldn't overriding the `blah` field in class B solve the issue?

 Unfortunately not -- you get the following error:

 {{{
 django.core.exceptions.FieldError: Local field 'blah' in class 'B' clashes
 with field of similar name from base class 'A'
 }}}

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Comment (by jezdez):

 Wouldn't overriding the `blah` field in class B solve the issue?

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-
Description changed by julien:

Old description:

> I'm dealing with this case:
>
> {{{#!python
> class A(models.Model):
> blah = models.CharField(max_length=100)
>
> class Meta:
> abstract = True
>
> class B(A):
> pass
> }}}
>
> ... where `A` is in a separate app than `B` and is used in multiple
> different contexts. I need to have the `blah` field be unique for `B`,
> whereas it shouldn't necessarily be unique in every other context where
> it is used. The only way I've found so far is:
>
> {{{#!python
> class B(A):
> pass
>
> B._meta.get_field('blah')._unique = True # Ugliness alert!
> }}}
>
> Is it envisageable to allow setting the `unique` flag for individual
> fields from the Meta options, in the same way as with `unique_together`?
> Something like this for example:
>
> {{{#!python
> class B(models.Model):
>
> class Meta:
> unique = ('blah',)
> }}}

New description:

 I'm dealing with this case:

 {{{#!python
 class A(models.Model):
 blah = models.CharField(max_length=100)

 class Meta:
 abstract = True

 class B(A):
 pass
 }}}

 ... where `A` is in a separate app than `B` and is used in multiple
 different contexts. I need to have the `blah` field be unique for `B`,
 whereas it shouldn't necessarily be unique in every other context where it
 is used. The only way I've found so far is:

 {{{#!python
 class B(A):
 pass

 B._meta.get_field('blah')._unique = True # Ugliness alert!
 }}}

 Is it envisageable to allow setting the `unique` flag for individual
 fields from the Meta options, in the same way as with `unique_together`?
 Something like this for example:

 {{{#!python
 class B(A):

 class Meta:
 unique = ('blah',)
 }}}

--

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Re: [Django] #15953: Allow setting individual fields as 'unique' from the model Meta options

[Django]

#15953: Allow setting individual fields as 'unique' from the model Meta options
-+-
   Reporter:  julien |  Owner:  nobody
   Type:  New| Status:  new
  feature|  Component:  Database layer
  Milestone: |  (models, ORM)
Version:  1.3|   Severity:  Normal
 Resolution: |   Keywords:
   Triage Stage: |  Has patch:  0
  Unreviewed |Needs tests:  0
Needs documentation:  0  |  Easy pickings:  0
Patch needs improvement:  0  |
-+-

Old description:

> I'm dealing with this case:
>
> {{{#!python
> class A(models.Model):
> blah = models.CharField(max_length=100)
>
> class Meta:
> abstract = True
>
> class B(models.Model):
> pass
> }}}
>
> ... where `A` is in a separate app than `B` and is used in multiple
> different contexts. I need to have the `blah` field be unique for `B`,
> whereas it shouldn't necessarily be unique in every other context where
> it is used. The only way I've found so far is:
>
> {{{#!python
> class B(models.Model):
> pass
>
> B._meta.get_field('blah')._unique = True # Ugliness alert!
> }}}
>
> Is it envisageable to allow setting the `unique` flag for individual
> fields from the Meta options, in the same way as with `unique_together`?
> Something like this for example:
>
> {{{#!python
> class B(models.Model):
>
> class Meta:
> unique = ('blah',)
> }}}

New description:

 I'm dealing with this case:

 {{{#!python
 class A(models.Model):
 blah = models.CharField(max_length=100)

 class Meta:
 abstract = True

 class B(A):
 pass
 }}}

 ... where `A` is in a separate app than `B` and is used in multiple
 different contexts. I need to have the `blah` field be unique for `B`,
 whereas it shouldn't necessarily be unique in every other context where it
 is used. The only way I've found so far is:

 {{{#!python
 class B(A):
 pass

 B._meta.get_field('blah')._unique = True # Ugliness alert!
 }}}

 Is it envisageable to allow setting the `unique` flag for individual
 fields from the Meta options, in the same way as with `unique_together`?
 Something like this for example:

 {{{#!python
 class B(models.Model):

 class Meta:
 unique = ('blah',)
 }}}

--

Comment (by julien):

 (fixed description: `B` inherits from `A`)

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