Improve your Django website speed
Over half of Django websites are being slowed down by inefficient code. This is a problem because customers leave slow websites.
Code Review Doctor checks that your code follows the Django documentation database best practices, and offers the fix to reduce developer effort.
This improves customer bounce rate by helping prevent your website from being slowed by inefficient code.
Code Review Doctor checks for the following database performance anti-patterns:
Using len(queryset) instead of queryset.count()
Using len(queryset) instead of queryset.count()
len(queryset) performs the count at application level. That is much less efficient than doing queryset.count(), which does the calculation at database level and just returns the count.
Not using foreign keys directly
Not using foreign keys directly
When working with foreign keys, accessing the related field will result in a database read. That can be eliminated by using *_id, which is the foreign key value that Django has already cached on the object to make this scenario more efficient.
Comparing queryset.count() instead of checking queryset.exists()
Comparing queryset.count() instead of checking queryset.exists()
Comparing queryset.count() is less efficient than checking queryset.exists(), so use querySet.count() if you only want the count, and use queryset.exists() if you only want to find out if at least one result exists.
Checking queryset truthiness instead of checking queryset.exists()
Checking queryset truthiness instead of checking queryset.exists()
This can load every row in the database table into memory because the queryset is evaluated. Checking if a queryset is truthy/falsey is much less efficient than checking queryset.exists().
Random ordering via order_by("?")
Random ordering via order_by("?")
Using order_by('?') can be very inefficient if you have lots of rows in the table. Moving the randomness to the application layer will probably give significant a performance improvement.
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