fix(translate): improved comments loading

Avoid repeated fetching of comment attributes while translating.

Fixes WEBLATE-36WD

Author: nijel

docs/changes.rst

@@ -84,6 +84,7 @@ Weblate 5.17
 * :doc:`/formats/android` now preserves template-defined escaped markup formatting when saving translations.
 * REST API component creation now handles temporary uploaded files for ``docfile`` and ``zipfile`` uploads.
 * SSH repository errors now distinguish changed host keys from missing host keys and avoid automatically trusting host key replacements.
+* Improved loading speed for comments on the translate page.
 
 .. rubric:: Compatibility
 

weblate/trans/models/comment.py

@@ -21,7 +21,8 @@
 if TYPE_CHECKING:
     from datetime import datetime
 
-    from weblate.auth.models import AuthenticatedHttpRequest, Unit, User
+    from weblate.auth.models import AuthenticatedHttpRequest, User
+    from weblate.trans.models.unit import Unit
 
 
 class CommentManager(models.Manager):
@@ -94,6 +95,9 @@ def add(
 
 
 class CommentQuerySet(models.QuerySet):
+    def prefetch(self):
+        return self.select_related("user")
+
     def order(self):
         return self.order_by("timestamp")
 

weblate/trans/models/unit.py

@@ -1834,12 +1834,20 @@ def active_checks(self) -> list[Check]:
     def all_comments(self) -> models.QuerySet[Comment]:
         """Return list of target comments."""
         if self.is_source:
-            # Add all comments on translation on source string comment
-            query = Q(unit__source_unit=self)
-        else:
-            # Add source string comments for translation unit
-            query = Q(unit__in=(self, self.source_unit))
-        return Comment.objects.filter(query).prefetch_related("unit", "user").order()
+            return (
+                Comment.objects.filter(unit__source_unit=self)
+                .prefetch()
+                .prefetch_related(
+                    "unit__translation__language",
+                    "unit__translation__component__project",
+                )
+                .order()
+            )
+        return (
+            (self.comment_set.all() | self.source_unit.comment_set.all())
+            .prefetch()
+            .order()
+        )
 
     @cached_property
     def unresolved_comments(self) -> list[Comment]:

weblate/trans/tests/test_comment.py

@@ -4,6 +4,8 @@
 
 """Tests for comment views."""
 
+from django.db import connection
+from django.test.utils import CaptureQueriesContext
 from django.urls import reverse
 
 from weblate.trans.models import Comment
@@ -155,3 +157,47 @@ def test_resolve_comment(self) -> None:
         comment.refresh_from_db()
         self.assertTrue(comment.resolved)
         self.assertFalse(comment.unit.has_comment)
+
+    def test_translate_comment_queries_do_not_scale_with_comment_count(self) -> None:
+        unit = self.get_unit()
+        self.make_manager()
+
+        def render_queries() -> int:
+            for _unused in range(2):
+                session = self.client.session
+                session.clear()
+                session.save()
+                response = self.client.get(
+                    unit.translation.get_translate_url(),
+                    {"checksum": unit.checksum},
+                )
+                self.assertEqual(response.status_code, 200)
+
+            session = self.client.session
+            session.clear()
+            session.save()
+            with CaptureQueriesContext(connection) as queries:
+                response = self.client.get(
+                    unit.translation.get_translate_url(),
+                    {"checksum": unit.checksum},
+                )
+            self.assertEqual(response.status_code, 200)
+            return len(queries)
+
+        Comment.objects.filter(unit__in=(unit, unit.source_unit)).delete()
+        Comment.objects.create(
+            unit=unit,
+            comment="Comment 0",
+            user=self.anotheruser,
+        )
+        baseline_queries = render_queries()
+
+        Comment.objects.filter(unit__in=(unit, unit.source_unit)).delete()
+        for index in range(5):
+            Comment.objects.create(
+                unit=unit,
+                comment=f"Comment {index}",
+                user=self.anotheruser,
+            )
+
+        self.assertEqual(render_queries(), baseline_queries)