Django 2.2 CheckContraint: how to check "min_foo < max_foo" ?

[Olivier]

hello,

Looking at [1], I can see examples where one can check at database level, that a model field min_foo satisfies a constraint such as "min_foo > 5".

How do you write a constraint involving two different fields like  "min_foo < max_foo" or "discounted_price < price" ?

PostgreSQL doc shows how to write such constraint but how to express those with Django 2.2 ?

[1] https://docs.djangoproject.com/en/2.2/ref/models/constraints/

Best regards

[Leonardo Rezende]

Hi,

   Didn't tested... Did you try the F expression?

from django.db import models

class Customer(models.Model):
    age = models.IntegerField()

    class Meta:
        constraints = [
            models.CheckConstraint(check=models.Q(discounted_price__lte=models.F('price')), name='age_gte_18'),
        ]

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Leonardo Rezende

[Olivier]

Yes, using things like models.F('price') made it !

Thank you very much, Leonardo, for this.

Le mercredi 13 novembre 2019 13:35:37 UTC+1, LRezende a écrit :

Hi,

   Didn't tested... Did you try the F expression?

from django.db import models

class Customer(models.Model):
    age = models.IntegerField()

    class Meta:
        constraints = [
            models.CheckConstraint(check=models.Q(discounted_price__lte=models.F('price')), name='age_gte_18'),
        ]

Em ter., 12 de nov. de 2019 às 14:14, Olivier <oza...@gmail.com> escreveu:

hello,

Looking at [1], I can see examples where one can check at database level, that a model field min_foo satisfies a constraint such as "min_foo > 5".

How do you write a constraint involving two different fields like  "min_foo < max_foo" or "discounted_price < price" ?

PostgreSQL doc shows how to write such constraint but how to express those with Django 2.2 ?

[1] https://docs.djangoproject.com/en/2.2/ref/models/constraints/

Best regards

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Leonardo Rezende