Django database indexes for query performance

                  from django.db import models
from django.contrib.postgres.indexes import GinIndex, BTreeIndex


class Order(models.Model):
    customer = models.ForeignKey('Customer', on_delete=models.CASCADE)
    status = models.CharField(max_length=20, db_index=True)
    total = models.DecimalField(max_digits=10, decimal_places=2)
    created_at = models.DateTimeField(auto_now_add=True, db_index=True)
    completed_at = models.DateTimeField(null=True, blank=True)

    class Meta:
        indexes = [
            # Compound index for common query
            models.Index(fields=['customer', 'status']),

            # Descending order index
            models.Index(fields=['-created_at']),

            # Partial index (PostgreSQL)
            models.Index(
                fields=['completed_at'],
                condition=models.Q(status='completed'),
                name='completed_orders_idx'
            ),

            # Covering index (includes extra columns)
            models.Index(
                fields=['status'],
                include=['total', 'created_at'],
                name='status_cover_idx'
            ),
        ]