bug 1462475: Remove zones from boosting

"boost" was 8.0 for zones, which is used in the SearchFilterBackend to
boost zone root results. In the future, the boost function could be
simplified.

kuma/wiki/search.py

@@ -7,7 +7,6 @@
 
 from celery import chain
 from django.conf import settings
-from django.core.exceptions import ObjectDoesNotExist
 from django.db.models import Q
 from django.utils.html import strip_tags
 from django.utils.translation import ugettext_lazy as _
@@ -70,8 +69,10 @@ def case_insensitive_keywords(cls, keywords):
 
     @classmethod
     def from_django(cls, obj):
+        is_root_document = (obj.slug.count('/') == 1)
         doc = {
             'id': obj.id,
+            'boost': 4.0 if is_root_document else 1.0,
             'title': obj.title,
             'slug': obj.slug,
             'summary': obj.get_summary_text(),
@@ -87,20 +88,6 @@ def from_django(cls, obj):
                 obj.extract.html_attributes()),
         }
 
-        # Check if the document has a document zone attached
-        try:
-            is_zone = bool(obj.zone)
-        except ObjectDoesNotExist:
-            is_zone = False
-
-        if is_zone:
-            # boost all documents that are a zone
-            doc['boost'] = 8.0
-        elif obj.slug.count('/') == 1:
-            # a little boost if no zone but still first level
-            doc['boost'] = 4.0
-        else:
-            doc['boost'] = 1.0
         if obj.parent:
             doc['parent'] = {
                 'id': obj.parent.id,