When querying for a Wagtail Page that has child (Subclassed) pages, you'll receive all of the pages in your QuerySet. There are times when you simply want the child pages (all types), a specific type of child page, or just the parent page itself with no children. In this lesson we'll explore Wagtails .not_exact_type() and .exact_type() methods.
There are several ways to query your Wagtail Pages and return QuerySets containing only the page classes you want. Below is some example code.
This example assumes that there are child (subclassed) pages that inherit form
parent_pages = BlogDetailPage.objects.live().exact_type(BlogDetailPage)
This example assumes each child page is inheriting from
BlogDetailPage. This will return a QuerySet of
BlogDetailPage's, not the actual class you'd be expecting.
child_pages = BlogDetailPage.objects.live().not_exact_type(BlogDetailPage)
If you're trying to query for all child pages that inherit from a parent page (ie.
BlogDetailPage), you'll receive a QuerySet of
BlogDetailPage's. To get the specific child pages, append
.specific() to your query.
child_pages = BlogDetailPage.objects.live().not_exact_type(BlogDetailPage).specific()
Wagtail is built for speed and efficiency. It's easy to get away from that and write code that performs terribly. So by default the
.specific() argument called defer is set to
.specific(defer=True)). Grabbing specific fields from a model means adding another database hit, and if the QuerySet is large, this can become a problem. So it's good that specific property deferring is enabled by default.
But occasionally you want the specific properties of a class. To disabled property deferring simply append
.specific(defer=False) to your ORM Query.
Wagtail comes with a lot of different QuerySet options. This lesson only went over 2 of them, but there are many more. Definitely take a couple minutes and read through their docs page.
This lesson works purely in the Django Shell and doesn't have any code to committed to the repo. Above is where you can find example code.