Unique model field in Django and case sensitivity (postgres)

Question

Consider the following situation: -

Suppose my app allows users to create the states / provinces in their country. Just for clarity, we are considering only ASCII ch

Answer 1

On the Postgres side of things, a functional unique index will let you enforce unique values without case. citext is also noted, but this will work with older versions of PostgreSQL and is a useful technique in general.

Example:

# create table foo(bar text);
CREATE TABLE
# create unique index foo_bar on foo(lower(bar));
CREATE INDEX
# insert into foo values ('Texas');
INSERT 0 1
# insert into foo values ('texas');
ERROR:  duplicate key value violates unique constraint "foo_bar"

Answer 2

You can use lookup='iexact' in UniqueValidator on serializer, like this:

class StateSerializer(serializers.ModelSerializer): 
    name = serializers.CharField(validators=[
    UniqueValidator(
        queryset=models.State.objects.all(),lookup='iexact'
    )]

django version: 1.11.6

Answer 3

You can do this by overwriting the Model's save method - see the docs. You'd basically do something like:

class State(models.Model):
    name = models.CharField(max_length=50, unique=True)

    def save(self, force_insert=False, force_update=False):
        if State.objects.get(name__iexact = self.name):
            return
        else:
            super(State, self).save(force_insert, force_update)

Also, I may be wrong about this, but the upcoming model-validation SoC branch will allow us to do this more easily.

Answer 4

Besides already mentioned option to override save, you can simply store all text in lower case in database and capitalize them on displaying.

class State(models.Model):
    name = models.CharField(max_length=50, unique=True)

    def save(self, force_insert=False, force_update=False):
        self.name = self.name.lower()
        super(State, self).save(force_insert, force_update)