Add method to prefetch for listing

website/blog/models.py

@@ -8,7 +8,7 @@ from modelcluster.fields import ParentalManyToManyField
 from wagtail.admin.panels import FieldPanel
 
 from website.common.models import BaseContentPage, BaseListingPage
-from website.common.utils import TocEntry
+from website.common.utils import TocEntry, prefetch_for_listing
 from website.common.views import ContentPageFeed
 
 
@@ -37,12 +37,8 @@ class BlogPostListPage(BaseListingPage):
         return [TocEntry(post_month, post_month, 0, []) for post_month in post_months]
 
     def get_listing_pages(self) -> models.QuerySet:
-        return (
-            BlogPostPage.objects.descendant_of(self)
-            .live()
-            .select_related("hero_image", "hero_unsplash_photo")
-            .prefetch_related("tags")
-            .order_by("-date", "title")
+        return prefetch_for_listing(
+            BlogPostPage.objects.descendant_of(self).live().order_by("-date", "title").prefetch_related("tags")
         )
 
     @property
@@ -117,9 +113,8 @@ class BlogPostCollectionPage(BaseListingPage):
     subpage_types = [BlogPostPage]
 
     def get_listing_pages(self) -> models.QuerySet:
-        return (
-            BlogPostPage.objects.child_of(self)
-            .select_related("hero_image", "hero_unsplash_photo")
+        return prefetch_for_listing(
+            BlogPostPage.objects.child_of(self).live()
             .prefetch_related("tags")
             .order_by("-date", "title")
         )

website/common/models.py

@@ -22,12 +22,18 @@ from wagtail.search import index
 from wagtail.snippets.models import register_snippet
 from wagtailmetadata.models import MetadataMixin
 
-from website.common.utils import count_words
 from website.contrib.unsplash.widgets import UnsplashPhotoChooser
 
 from .serializers import PaginationSerializer
 from .streamfield import add_heading_anchors, get_blocks, get_content_html
-from .utils import TocEntry, extract_text, get_table_of_contents, truncate_string
+from .utils import (
+    TocEntry,
+    count_words,
+    extract_text,
+    get_table_of_contents,
+    prefetch_for_listing,
+    truncate_string,
+)
 
 
 class BasePage(Page):
@@ -196,12 +202,8 @@ class BaseListingPage(RoutablePageMixin, BaseContentPage):
         abstract = True
 
     def get_listing_pages(self) -> models.QuerySet:
-        return (
-            self.get_children()
-            .live()
-            .specific()
-            .select_related("hero_image", "hero_unsplash_photo")
-            .order_by("title")
+        return prefetch_for_listing(
+            self.get_children().live().specific().order_by("title")
         )
 
     def get_paginator_page(self) -> PaginatorPage:

website/common/utils.py

@@ -9,6 +9,7 @@ from django.utils.text import slugify, smart_split
 from more_itertools import ilen
 from wagtail.models import Page
 from wagtail.models import get_page_models as get_wagtail_page_models
+from wagtail.query import PageQuerySet
 
 HEADER_TAGS = ["h2", "h3", "h4", "h5", "h6"]
 
@@ -84,3 +85,13 @@ def extract_text(html: str) -> str:
 
 def truncate_string(text: str, words: int) -> str:
     return " ".join(islice(smart_split(text), words))
+
+
+def prefetch_for_listing(queryset: PageQuerySet) -> PageQuerySet:
+    """
+    Prefetch a queryset ready for listing.
+
+    This should be a queryset method, but dealing with lots of
+    different page models is a pain.
+    """
+    return queryset.select_related("hero_image", "hero_unsplash_photo")

website/search/models.py

@@ -10,7 +10,7 @@ from wagtail.models import Page
 from wagtail.search.utils import parse_query_string
 
 from website.common.models import BaseContentPage
-from website.common.utils import TocEntry
+from website.common.utils import TocEntry, prefetch_for_listing
 from website.home.models import HomePage
 
 from .serializers import MIN_SEARCH_LENGTH, SearchParamsSerializer
@@ -75,10 +75,8 @@ class SearchPage(RoutablePageMixin, BaseContentPage):
             results = paginator.page(page_num)
 
             # HACK: Search results aren't a queryset, so we can't call `.specific` on it. This forces it to one as efficiently as possible
-            results.object_list = (
-                results.object_list.get_queryset()
-                .specific()
-                .select_related("hero_image", "hero_unsplash_photo")
+            results.object_list = prefetch_for_listing(
+                results.object_list.get_queryset().specific()
             )
 
         except EmptyPage: