Define indexes on Embedded Models in Top-Level Model

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      Context

      Currently, if a user wants to define an index on an embedded field within a model, they have to do this within the `EmbeddedModel` abstraction. Conceptually this doesn't make sense as EmbeddedModels are not collections themselves, so they allow for reusability between top-level models. We did this at first because top level models validate the existence of a field and there existed built-in method to validate embedded fields prior to the django-mongodb-backend. We need to change this to support index definitions at top-level embedded models.

       

       

      class Address(EmbeddedModel):
    unique_constraint_one = models.CharField(max_length=10)
class Author(EmbeddedModel):
    address = EmbeddedModelField(Address)
    unique_constraint_two = models.CharField(max_length=10)
class Book(models.Model):
    author = EmbeddedModelField(Author)
    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["author.unique_constraint_two"],
                name="unique_two",
            ),
            models.UniqueConstraint(
                fields=["author.address.unique_constraint_one"],
                name="unique_one",
            ),
        ]

      Definition of done

      Change the above to support this syntax:

       

       

      class Address(EmbeddedModel):
    unique_together_one = models.CharField(max_length=10)
    unique_together_two = models.CharField(max_length=10)
    class Meta:
        app_label = "schema_"
class Author(EmbeddedModel):
    address = EmbeddedModelField(Address)
    unique_together_three = models.CharField(max_length=10)
    unique_together_four = models.CharField(max_length=10)
    class Meta:
        app_label = "schema_"
class Book(models.Model):
    author = EmbeddedModelField(Author)
    class Meta:
        app_label = "schema_"
        constraints = [
            models.UniqueConstraint(
                F("author__unique_together_three").asc(),
                F("author__unique_together_four").desc(),
                name="unique_together_34",
            ),
            (
                models.UniqueConstraint(
                    F("author_address_unique_together_one"),
                    F("author_address_unique_together_two").asc(),
                    name="unique_together_12",
                )
            ),
        ]
 

       

      Pitfalls

      Using `F` expressions may be cumbersome in the eyes of the end-user. As a mitigation we could implement a light wrapper (afterwards) that converts dot notation (mongodb's standard way of identifying subfields) into `__` notation. 

            Assignee:
            Emanuel Lupi
            Reporter:
            Jib Adegunloye
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              Created:
              Updated:
              Resolved: