indexes.rst

Indexes

Unique Index

The ~psqlextra.indexes.UniqueIndex lets you create a unique index. Normally Django only allows you to create unique indexes by specifying unique=True on the model field.

Although it can be used on any Django model, it is most useful on views and materialized views where unique=True does not work.

from django.db import models
from psqlextra.indexes import UniqueIndex

class Model(models.Model):
    class Meta:
        indexes = [
            UniqueIndex(fields=['name']),
        ]

    name = models.CharField(max_length=255)

Model.objects.create(name='henk')
Model.objects.create(name='henk') # raises IntegrityError

Conditional Unique Index

The ~psqlextra.indexes.ConditionalUniqueIndex lets you create partial unique indexes in case you ever need ~django:django.db.models.Options.unique_together constraints on nullable columns.

Warning

In Django 3.1 or newer, you might want to use ~django.db.models.indexes.condition instead.

Before:

from django.db import models

class Model(models.Model):
    class Meta:
        unique_together = ['a', 'b']

    a = models.ForeignKey('some_model', null=True)
    b = models.ForeignKey('some_other_model')

# Works like a charm!
b = B()
Model.objects.create(a=None, b=b)
Model.objects.create(a=None, b=b)

After:

from django.db import models
from psqlextra.indexes import ConditionalUniqueIndex

class Model(models.Model):
    class Meta:
        indexes = [
            ConditionalUniqueIndex(fields=['a', 'b'], condition='"a" IS NOT NULL'),
            ConditionalUniqueIndex(fields=['b'], condition='"a" IS NULL')
        ]

    a = models.ForeignKey('some_model', null=True)
    b = models.ForeignKey('some_other_model')

# Integrity Error!
b = B()
Model.objects.create(a=None, b=b)
Model.objects.create(a=None, b=b)

Case Insensitive Unique Index

The ~psqlextra.indexes.CaseInsensitiveUniqueIndex lets you create an index that ignores the casing for the specified field(s).

This makes the field(s) behave more like a text field in MySQL.

from django.db import models
from psqlextra.indexes import CaseInsensitiveUniqueIndex

class Model(models.Model):
    class Meta:
        indexes = [
            CaseInsensitiveUniqueIndex(fields=['name']),
        ]

    name = models.CharField(max_length=255)

Model.objects.create(name='henk')
Model.objects.create(name='Henk') # raises IntegrityError