Unique Without Index

Description

This check identifies fields that are marked as unique (unique=True) but do not have a database index (db_index=False). It recommends adding an index to the unique field to improve query performance.

Rationale

Adding an index to a unique field can significantly speed up lookups for unique values, making queries more efficient. This improves the overall performance of your database and can help reduce query execution time.

Example

Consider the following model:

from django.db import models

class MyModel(models.Model):
    name = models.CharField(max_length=100, unique=True)

The name field is marked as unique but does not have an index. The check would detect this and recommend adding an index:

class MyModel(models.Model):
    name = models.CharField(max_length=100, unique=True, db_index=True)

By adding an index to the unique field, you can improve the performance of queries involving this field.