"Cannot reorder a query once a slice has been taken." - Pagination is not supported

[vdboor]

Due to the use of jqTree, the tree should start with root nodes only. This breaks with pagination, causing the error:

Cannot reorder a query once a slice has been taken.

This happens because the adminlist_recursetree attempts to sort the tree on lft value. To really fix this issue, the next page should start with the first root too. That could be implemented by using a custom paginator on the parent admin.

[borgstrom]

I believe I've just run into this issue while using django-fluent-pages.

Is there any way to work around it?

[vdboor]

You can set list_per_page to a very high value, e.g. 5000.

Clearly, I have to look into this issue pretty soon.

[borgstrom]

Since the ModelAdmin is part of django-fluent-pages can you please provide direction on where I should set the list_per_page value.

I'll subclass your ModelAdmin and register it instead of the original, but which one should I be subclassing to add the list_per_page value?

[vdboor]

Glad you've asked. This turned out to be a bit less intuitive then I thought.
You can add the following code to a admin.py or __init__.py file:

from fluent_pages.admin import UrlNodePolymorphicAdmin
UrlNodePolymorphicAdmin.list_per_page = 10000

UPDATE: I've just released a new version of django-polymorphic-tree which includes this workaround.

FYI, The polymorhic admin is implemented by registering one class in the admin, and proxying the add_view, change_view and delete_view to your model admin. That's why the value needs to be set to that particular class.

Fun fact: both that logic and this package were originally part of django-fluent-pages, and got split out or were upstreamed.

[borgstrom]

The workaround is working good. Thanks!