refactor: reduce query fetch for determining header data

Author: julhoang

core/context_processors.py

@@ -9,9 +9,20 @@
 from versions.models import Version
 
 
+def _get_header_version_data(request):
+    """Per-request shared accessor so `current_version` and `selected_version`
+    share one DB fetch within a single request."""
+    cached = getattr(request, "_header_version_data", None)
+    if cached is not None:
+        return cached
+    data = Version.objects.get_header_dropdown_data()
+    request._header_version_data = data
+    return data
+
+
 def current_version(request):
     """Custom context processor that adds the current release to the context"""
-    return {"current_version": Version.objects.most_recent()}
+    return {"current_version": _get_header_version_data(request).most_recent}
 
 
 def selected_version(request):
@@ -65,12 +76,17 @@ def selected_version(request):
     is_url_driven = bool(url_version_slug)
     cookie_slug = get_version_from_cookie(request)
 
+    header_data = _get_header_version_data(request)
+    options = list(header_data.options)
+
     resolved_slug = url_version_slug or cookie_slug
     version = None
     if resolved_slug and resolved_slug != LATEST_RELEASE_URL_PATH_STR:
-        version = Version.objects.filter(slug=resolved_slug).first()
+        version = next((v for v in options if v.slug == resolved_slug), None)
+        if version is None:
+            version = Version.objects.filter(slug=resolved_slug).first()
     if version is None:
-        version = Version.objects.most_recent()
+        version = header_data.most_recent
 
     is_explicit_non_latest_url = bool(
         url_version_slug and url_version_slug != LATEST_RELEASE_URL_PATH_STR
@@ -84,9 +100,6 @@ def selected_version(request):
 
     label = version.display_name if (is_explicit and version) else "Latest"
 
-    # Materialize: _annotate_option_hrefs mutates each option with a `.href`.
-    options = list(Version.objects.get_dropdown_versions())
-
     latest_href = ""
     if is_url_driven and resolver_match and resolver_match.view_name:
         latest_href = _annotate_option_hrefs(

news/tests/test_views.py

@@ -419,7 +419,7 @@ def test_news_create_get(tp, regular_user, url_name, form_class):
         # assertGoodView expects a resolved URL
         # see https://github.com/revsys/django-test-plus/issues/202
         url = tp.reverse(url_name)
-        tp.assertGoodView(url, test_query_count=4, verbose=True)
+        tp.assertGoodView(url, test_query_count=5, verbose=True)
 
     form = tp.get_context("form")
     assert isinstance(form, form_class)

versions/managers.py

@@ -1,3 +1,5 @@
+from typing import NamedTuple
+
 from django.db import models
 from django.db.models import Func, Value, Count, Q
 from django.db.models.functions import Replace
@@ -9,6 +11,14 @@
 )
 
 
+class HeaderVersionData(NamedTuple):
+    """Consolidated data needed to render the navbar version dropdown."""
+
+    options: list
+    most_recent: "Version | None"  # noqa: F821
+    most_recent_beta: "Version | None"  # noqa: F821
+
+
 class VersionQuerySet(models.QuerySet):
     def active(self):
         """Return active versions"""
@@ -166,6 +176,49 @@ def should_show_beta(most_recent_beta):
 
         return queryset.order_by(order_by)
 
+    def get_header_dropdown_data(self) -> HeaderVersionData:
+        """Single-query fetch for the navbar version dropdown.
+
+        Replaces the 3-4 queries from calling `most_recent()`,
+        `most_recent_beta()`, and `get_dropdown_versions()` separately. Dropdown
+        list matches `get_dropdown_versions()` for the header's use case only —
+        no develop/master, no library filtering.
+        """
+        name_exclusions = [
+            "head",
+            MASTER_RELEASE_URL_PATH_STR,
+            DEVELOP_RELEASE_URL_PATH_STR,
+        ]
+        versions = list(
+            self.active()
+            .filter(Q(full_release=True) | Q(beta=True))
+            .exclude(name__in=name_exclusions)
+            .defer("data")
+            .order_by("-name")
+        )
+
+        most_recent = next((v for v in versions if not v.beta and v.full_release), None)
+        most_recent_beta = next((v for v in versions if v.beta), None)
+
+        include_beta = (
+            most_recent_beta is not None
+            and most_recent is not None
+            and most_recent_beta.cleaned_version_parts
+            > most_recent.cleaned_version_parts
+        )
+        if include_beta:
+            options = [
+                v for v in versions if not v.beta or v.name == most_recent_beta.name
+            ]
+        else:
+            options = [v for v in versions if not v.beta]
+
+        return HeaderVersionData(
+            options=options,
+            most_recent=most_recent,
+            most_recent_beta=most_recent_beta,
+        )
+
 
 class VersionFileQuerySet(models.QuerySet):
     def active(self):