How to Sort with NULLS LAST in Django Queries Using Postgresql?

Handling NULL Values in Django Queries with "NULLS LAST"

Sorting models in Postgresql often requires handling NULL values effectively. Django provides a convenient method to incorporate the "NULLS LAST" optimization into queries, allowing you to control the ordering of null values.

Consider the following scenario:

Problem:
You want to sort a model using the Postgresql "NULLS LAST" option to move null values to the end of the ordered sequence. However, your attempt using extra(order_by=('-price', 'NULLS LAST')) fails with the error "Cannot resolve keyword 'NULLS LAST' into field."

Solution:
To achieve "NULLS LAST" ordering in Django, use the F expression and set the nulls_last parameter in the desc() method of the field expression. For example:

MyModel.objects.all().order_by(F('price').desc(nulls_last=True))

This syntax leverages Django's expression API, which allows you to construct complex filters and sorting criteria using field expressions (in this case, F('price')), and customize the sorting behavior using parameters like nulls_last.

It's important to note that this functionality was introduced in Django 1.11. Refer to the Django documentation for the relevant version you're using, as there may be variations in syntax or supported features.

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