Improve the performance of get_region_links (#3120)

* Improve region link loading performance

Time for running the `get_urls` query (without the prefetch):
- Augsburg: 1829ms → 190ms (90% reduction)
- München: 2037ms → 424ms (80% reduction)

I achieved another 30-40% reduction by adding an index to `Link`,
though this will have to be a pr for django-linkcheck

* Only prefetch region links if required

Prefetching the region links normally takes more than the actual
query, so not doing it if possible saves a lot of time

integreat_cms/cms/utils/linkcheck_utils.py

@@ -32,12 +32,14 @@
 def get_urls(
     region_slug: str | None = None,
     url_ids: Any | None = None,
+    prefetch_region_links: bool = False,
 ) -> list[Url] | QuerySet[Url]:
     """
     Collect all the urls which appear in the latest versions of the contents of the region, filtered by ID or region if given.
 
     :param region_slug: The slug of the current region
     :param url_ids: The list of requested url ids
+    :param prefetch_region_links: Whether to prefetch region links
     :return: The list (or queryset) of urls
     """
     urls = Url.objects.all()
@@ -49,17 +51,15 @@ def get_urls(
         region_links = get_region_links(region)
 
         # Prefetch all link objects of the requested region
-        urls = (
-            urls.filter(links__in=region_links)
-            .distinct()
-            .prefetch_related(
+        urls = urls.filter(links__in=region_links).distinct()
+        if prefetch_region_links:
+            urls = urls.prefetch_related(
                 Prefetch(
                     "links",
                     queryset=region_links,
                     to_attr="region_links",
                 )
             )
-        )
 
     # Annotate with number of links that are not ignored.
     # If there is any link that is not ignored, the url is also not ignored.
@@ -107,14 +107,18 @@ def get_region_links(region: Region) -> QuerySet:
     organizations = Organization.objects.filter(region=region, archived=False)
     # Get all link objects of the requested region
     region_links = Link.objects.filter(
-        Q(page_translation__id__in=latest_pagetranslation_versions)
-        | Q(imprint_translation__id__in=latest_imprinttranslation_versions)
-        | Q(event_translation__id__in=latest_eventtranslation_versions)
-        | Q(poi_translation__id__in=latest_poitranslation_versions)
-        | Q(organization__id__in=organizations)
-    ).order_by("id")
+        page_translation__id__in=latest_pagetranslation_versions
+    ).union(
+        Link.objects.filter(
+            imprint_translation__id__in=latest_imprinttranslation_versions
+        ),
+        Link.objects.filter(event_translation__id__in=latest_eventtranslation_versions),
+        Link.objects.filter(poi_translation__id__in=latest_poitranslation_versions),
+        Link.objects.filter(organization__id__in=organizations),
+        all=True,
+    )
 
-    return region_links
+    return Link.objects.filter(id__in=region_links.values("pk")).order_by("id")
 
 
 def get_url_count(region_slug: str | None = None) -> dict[str, int]:
@@ -132,16 +136,20 @@ def get_url_count(region_slug: str | None = None) -> dict[str, int]:
 def filter_urls(
     region_slug: str | None = None,
     url_filter: str | None = None,
+    prefetch_region_links: bool = False,
 ) -> tuple[list[Url], dict[str, int]]:
     """
     Filter all urls of one region by the given category
 
     :param region_slug: The slug of the current region
     :param url_filter: Which urls should be returned (one of ``valid``, ``invalid``, ``ignored``, ``unchecked``).
                         If parameter is not in these choices or omitted, all urls are returned by default.
+    :param prefetch_region_links: Whether to prefetch region links
     :return: A tuple of the requested urls and a dict containing the counters of all remaining urls
     """
-    urls = get_urls(region_slug=region_slug)
+    urls = get_urls(
+        region_slug=region_slug, prefetch_region_links=prefetch_region_links
+    )
     # Split url lists into their respective categories
     ignored_urls, valid_urls, invalid_urls, email_links, phone_links, unchecked_urls = (
         [] for _ in range(6)

integreat_cms/cms/views/dashboard/dashboard_view.py

@@ -147,7 +147,9 @@ def get_broken_links_context(
 
         :return: Dictionary containing the context for broken links
         """
-        invalid_urls = filter_urls(request.region.slug, "invalid")[0]
+        invalid_urls = filter_urls(
+            request.region.slug, "invalid", prefetch_region_links=True
+        )[0]
         invalid_url = invalid_urls[0] if invalid_urls else None
 
         relevant_translation = (

integreat_cms/cms/views/linkcheck/linkcheck_list_view.py

@@ -90,7 +90,9 @@ def get_queryset(self) -> list[Url]:
         :return: The QuerySet of the filtered urls
         """
         urls, count_dict = filter_urls(
-            self.kwargs.get("region_slug"), self.kwargs.get("url_filter")
+            self.kwargs.get("region_slug"),
+            self.kwargs.get("url_filter"),
+            prefetch_region_links=True,
         )
         self.extra_context.update(count_dict)
         return urls
@@ -102,7 +104,9 @@ def dispatch(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpRespo
         if edit_url_id := kwargs.pop("url_id", None):
             region = request.region.slug if request.region else None
             try:
-                self.instance = get_urls(region, url_ids=[edit_url_id])[0]
+                self.instance = get_urls(
+                    region, url_ids=[edit_url_id], prefetch_region_links=True
+                )[0]
             except IndexError as e:
                 raise Http404("This URL does not exist") from e
             if request.POST: