diff options
| -rw-r--r-- | docs/topics/serialization.txt | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/docs/topics/serialization.txt b/docs/topics/serialization.txt index b81a552ff9..f95db92c16 100644 --- a/docs/topics/serialization.txt +++ b/docs/topics/serialization.txt @@ -387,7 +387,12 @@ Consider the following two models:: birthdate = models.DateField() class Meta: - unique_together = [['first_name', 'last_name']] + constraints = [ + models.UniqueConstraint( + fields=["first_name", "last_name"], + name="unique_first_last_name", + ), + ] class Book(models.Model): name = models.CharField(max_length=100) @@ -431,7 +436,12 @@ name:: objects = PersonManager() class Meta: - unique_together = [['first_name', 'last_name']] + constraints = [ + models.UniqueConstraint( + fields=["first_name", "last_name"], + name="unique_first_last_name", + ), + ] Now books can use that natural key to refer to ``Person`` objects:: @@ -454,12 +464,12 @@ into the primary key of an actual ``Person`` object. Whatever fields you use for a natural key must be able to uniquely identify an object. This will usually mean that your model will - have a uniqueness clause (either unique=True on a single field, or - ``unique_together`` over multiple fields) for the field or fields - in your natural key. However, uniqueness doesn't need to be - enforced at the database level. If you are certain that a set of - fields will be effectively unique, you can still use those fields - as a natural key. + have a uniqueness clause (either ``unique=True`` on a single field, or a + ``UniqueConstraint`` or ``unique_together`` over multiple fields) for the + field or fields in your natural key. However, uniqueness doesn't need to be + enforced at the database level. If you are certain that a set of fields + will be effectively unique, you can still use those fields as a natural + key. Deserialization of objects with no primary key will always check whether the model's manager has a ``get_by_natural_key()`` method and if so, use it to @@ -479,7 +489,12 @@ Firstly, you need to add another method -- this time to the model itself:: objects = PersonManager() class Meta: - unique_together = [['first_name', 'last_name']] + constraints = [ + models.UniqueConstraint( + fields=["first_name", "last_name"], + name="unique_first_last_name", + ), + ] def natural_key(self): return (self.first_name, self.last_name) |