Optimizing Performance in Django: Eliminating Left Outer Joins with Subqueries and django-sql-utils

I was having performance issues with my project and noticed that the SQL queries to the database through django-debug-toolbar were taking a long time. Upon investigating the queries, I found that a LEFT OUTER JOIN was causing the issue. I needed to add annotations to count the number of child instances associated with an instance.

Initially, the SQL query and custom queryset method were quite complex, so I rewrote it using Subquery to remove the LEFT OUTER JOIN. However, the new Django code was a bit harder to read, so I found the django-sql-utils library to simplify the code.

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