API search order has no effect

Steps to reproduce:

• use wagtail 1.9 & elasticsearch 2 or any version of wagtail-pg-search-backend
• install Wagtail’s API
• go to http://localhost:8000/api/v2/pages/?search=a+non-empty+search&order=first_published_at where you replace a+non-empty+search with any search query that returns results
• go to http://localhost:8000/api/v2/pages/?search=a+non-empty+search&order=-first_published_at (with the same replacement as before)
• compare the results

As you should see, ordering has no effect on the actual order of results. I discovered this issue while trying to implement search ordering (not to be confused with ranking) in wagtail-pg-search-backend. And I couldn’t find how to do it with the current way search is implemented.

So I guess searching doesn’t handle custom ordering. Unfortunately, the opposite is written in the docs, even with details on how to use it.

[m1kola]

#5318 should hopefully fix the issue with API. To make code snippets work from my previous comment - we will also need to make changes in the elastcisearch backends. I think it’s a separate issue so I created #5319

[m1kola]

I recently hand a similar issue with:

• Elasticsearch 5
• Django 2.1.3 and 2.1.5
• Wagtail 2.3 and 2.4. Pretty sure it affects 2.5 too.

This happens because Wagtail API sets reverse order using the reverse() on a QuerySet:

https://github.com/wagtail/wagtail/blob/58135ccf6ea06095379c32e07578095545b37762/wagtail/api/v2/filters.py#L79-L95

And Elasticsearch backends do not detect reverse order set using this method:

https://github.com/wagtail/wagtail/blob/58135ccf6ea06095379c32e07578095545b37762/wagtail/search/backends/base.py#L120-L140

Note that wagtail.contrib.postgres_search.backend doesn’t use _get_order_by method, so it works with fine.

---

Examples using code. This one works as expected with Elasticsearch search backend:

from wagtail.core.models import Page
from wagtail.search.backends import get_search_backend

search_query = 'social'
queryset = Page.objects.order_by('-first_published_at')

sb = get_search_backend()
results = sb.search(search_query, queryset, operator=None, order_by_relevance=False)

for r in results[:10]:
    print(r.pk, r.title)

This one will return results in different (ascending?) order:

from wagtail.core.models import Page
from wagtail.search.backends import get_search_backend

search_query = 'social'
queryset = Page.objects.order_by('first_published_at')
queryset = queryset.reverse()

sb = get_search_backend()
results = sb.search(search_query, queryset, operator=None, order_by_relevance=False)

for r in results[:10]:
    print(r.pk, r.title)