Override functionality

backend/courses/management/commands/cache_course_reviews.py

@@ -0,0 +1,71 @@
+import django.utils.timezone as timezone
+from django.core.management.base import BaseCommand
+from django.db import transaction
+from tqdm import tqdm
+
+from courses.models import Course, Section, course_reviews, sections_with_reviews
+
+
+REVIEW_FIELDS = [
+    "course_quality",
+    "difficulty",
+    "instructor_quality",
+    "work_required",
+]
+
+PREFIX = "precompute_"
+
+fields_to_update = [f"{PREFIX}{field}" for field in REVIEW_FIELDS] + ["annotation_expiration"]
+
+
+class Command(BaseCommand):
+    help = "Calculates and persists review averages for Course and Section."
+
+    def handle(self, *args, **options):
+        self.stdout.write("Calculating Course review averages...")
+        self.update_courses()
+        self.stdout.write(self.style.SUCCESS("Finished calculating Course review averages."))
+
+        self.stdout.write("Calculating Section review averages...")
+        self.update_sections()
+        self.stdout.write(self.style.SUCCESS("Finished calculating Section review averages."))
+
+    def update_courses(self):
+        queryset = course_reviews(
+            Course.objects.all(),
+        )
+
+        courses_to_update = []
+
+        for course in tqdm(queryset, desc="Updating Courses", file=self.stdout):
+            for field in REVIEW_FIELDS:
+                setattr(course, f"{PREFIX}{field}", getattr(course, field))
+            course.annotation_expiration = timezone.now() + timezone.timedelta(days=30)
+            courses_to_update.append(course)
+
+        with transaction.atomic():
+            Course.objects.bulk_update(
+                courses_to_update,
+                fields_to_update,
+                batch_size=500,
+            )
+
+    def update_sections(self):
+        queryset = sections_with_reviews(
+            Section.objects.all(),
+        )
+
+        sections_to_update = []
+
+        for section in tqdm(queryset, desc="Updating Sections", file=self.stdout):
+            for field in REVIEW_FIELDS:
+                setattr(section, f"{PREFIX}{field}", getattr(section, field))
+            section.annotation_expiration = timezone.now() + timezone.timedelta(days=30)
+            sections_to_update.append(section)
+
+        with transaction.atomic():
+            Section.objects.bulk_update(
+                sections_to_update,
+                fields_to_update,
+                batch_size=500,
+            )

backend/courses/migrations/0069_course_course_quality_course_difficulty_and_more.py

@@ -0,0 +1,59 @@
+# Generated by Django 5.0.2 on 2026-02-13 21:53
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("courses", "0068_merge_20250819_1758"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="course",
+            name="course_quality",
+            field=models.DecimalField(
+                blank=True,
+                decimal_places=3,
+                help_text="\nThe average course quality rating for this course, on a scale from 0 to 5 (precomputed for efficiency).\n",
+                max_digits=4,
+                null=True,
+            ),
+        ),
+        migrations.AddField(
+            model_name="course",
+            name="difficulty",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="course",
+            name="instructor_quality",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="course",
+            name="work_required",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="section",
+            name="course_quality",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="section",
+            name="difficulty",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="section",
+            name="instructor_quality",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="section",
+            name="work_required",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+    ]

backend/courses/migrations/0070_rename_difficulty_course_precompute_difficulty_and_more.py

@@ -0,0 +1,74 @@
+# Generated by Django 5.0.2 on 2026-02-26 21:29
+
+import django.utils.timezone
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("courses", "0069_course_course_quality_course_difficulty_and_more"),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name="course",
+            old_name="difficulty",
+            new_name="precompute_difficulty",
+        ),
+        migrations.RenameField(
+            model_name="course",
+            old_name="instructor_quality",
+            new_name="precompute_instructor_quality",
+        ),
+        migrations.RenameField(
+            model_name="course",
+            old_name="work_required",
+            new_name="precompute_work_required",
+        ),
+        migrations.RenameField(
+            model_name="section",
+            old_name="course_quality",
+            new_name="precompute_course_quality",
+        ),
+        migrations.RenameField(
+            model_name="section",
+            old_name="difficulty",
+            new_name="precompute_difficulty",
+        ),
+        migrations.RenameField(
+            model_name="section",
+            old_name="instructor_quality",
+            new_name="precompute_instructor_quality",
+        ),
+        migrations.RenameField(
+            model_name="section",
+            old_name="work_required",
+            new_name="precompute_work_required",
+        ),
+        migrations.RemoveField(
+            model_name="course",
+            name="course_quality",
+        ),
+        migrations.AddField(
+            model_name="course",
+            name="annotation_expiration",
+            field=models.DateTimeField(
+                default=django.utils.timezone.now,
+                help_text="\nThe expiration time for the annotations of this course, these fields should be refreshed\nevery month\n",
+            ),
+        ),
+        migrations.AddField(
+            model_name="course",
+            name="precompute_course_quality",
+            field=models.DecimalField(blank=True, decimal_places=3, max_digits=4, null=True),
+        ),
+        migrations.AddField(
+            model_name="section",
+            name="annotation_expiration",
+            field=models.DateTimeField(
+                default=django.utils.timezone.now,
+                help_text="\nThe expiration time for the annotations of this section, these fields should\nbe refreshed every month\n",
+            ),
+        ),
+    ]

backend/courses/models.py

@@ -7,7 +7,7 @@
 from django.core.exceptions import ValidationError
 from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db import models, transaction
-from django.db.models import OuterRef, Q, Subquery, UniqueConstraint
+from django.db.models import F, OuterRef, Q, Subquery, UniqueConstraint
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 from django.utils import timezone
@@ -89,7 +89,7 @@ def __str__(self):
         return self.code
 
 
-def sections_with_reviews(queryset):
+def sections_with_reviews(queryset, prefix=""):
     from review.views import section_filters_pcr
 
     # ^ imported here to avoid circular imports
@@ -109,11 +109,12 @@ def sections_with_reviews(queryset):
             & Q(course__topic=OuterRef("course__topic"))
             & Q(instructors__in=instructors_subquery)
         ),
+        prefix=prefix,
         extra_metrics=False,
     ).order_by("code")
 
 
-def course_reviews(queryset):
+def course_reviews(queryset, prefix=""):
     from review.views import section_filters_pcr
 
     # ^ imported here to avoid circular imports
@@ -122,13 +123,32 @@ def course_reviews(queryset):
         queryset,
         reviewbit_subfilters=(Q(review__section__course__topic=OuterRef("topic"))),
         section_subfilters=(section_filters_pcr & Q(course__topic=OuterRef("topic"))),
+        prefix=prefix,
         extra_metrics=False,
     )
 
 
+def cache_or_compute_course_reviews(queryset):
+    """
+    A helper function which takes a Course queryset and annotates it with review averages, either by
+    using cached precompute fields if the annotations have not expired or by computing the averages
+    from the reviews if they have expired or are missing.
+    """
+    if queryset.filter(annotation_expiration__lt=timezone.now()).exists():
+        return course_reviews(queryset).order_by("full_code", "semester")
+
+    return queryset.annotate(
+        course_quality=F("precompute_course_quality"),
+        instructor_quality=F("precompute_instructor_quality"),
+        difficulty=F("precompute_difficulty"),
+        work_required=F("precompute_work_required"),
+    ).order_by("full_code", "semester")
+
+
 class CourseManager(models.Manager):
     def get_queryset(self):
-        return course_reviews(super().get_queryset())
+        queryset = super().get_queryset()
+        return cache_or_compute_course_reviews(queryset)
 
 
 class Course(models.Model):
@@ -281,6 +301,31 @@ class Course(models.Model):
         ),
     )
 
+    annotation_expiration = models.DateTimeField(
+        default=timezone.now,
+        help_text=dedent(
+            """
+            The expiration time for the annotations of this course, these fields should be refreshed
+            every month
+            """
+        ),
+    )
+    precompute_course_quality = models.DecimalField(
+        max_digits=4,
+        decimal_places=3,
+        null=True,
+        blank=True,
+    )
+    precompute_instructor_quality = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+    precompute_difficulty = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+    precompute_work_required = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+
     class Meta:
         unique_together = (
             ("department", "code", "semester"),
@@ -554,9 +599,27 @@ def __str__(self):
         return f"{self.code} - {self.restriction_type} - {self.description}"
 
 
+def cache_or_compute_section_reviews(queryset):
+    """
+    A helper function which takes a Section queryset and annotates it with review averages, either
+    by using cached precompute fields if the annotations have not expired or by computing the
+    averages if they have expired or are missing.
+    """
+    if queryset.filter(annotation_expiration__lt=timezone.now()).exists():
+        return sections_with_reviews(queryset).order_by("full_code")
+
+    return queryset.annotate(
+        course_quality=F("precompute_course_quality"),
+        instructor_quality=F("precompute_instructor_quality"),
+        difficulty=F("precompute_difficulty"),
+        work_required=F("precompute_work_required"),
+    ).order_by("full_code")
+
+
 class SectionManager(models.Manager):
     def get_queryset(self):
-        return sections_with_reviews(super().get_queryset()).distinct()
+        queryset = super().get_queryset()
+        return cache_or_compute_section_reviews(queryset)
 
 
 class PreNGSSRestriction(models.Model):
@@ -827,6 +890,28 @@ class Meta:
         help_text="The number of active PCA registrations watching this section.",
     )  # For the set of PCA registrations for this section, use the related field `registrations`.
 
+    annotation_expiration = models.DateTimeField(
+        default=timezone.now,
+        help_text=dedent(
+            """
+            The expiration time for the annotations of this section, these fields should
+            be refreshed every month
+            """
+        ),
+    )
+    precompute_course_quality = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+    precompute_instructor_quality = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+    precompute_difficulty = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+    precompute_work_required = models.DecimalField(
+        max_digits=4, decimal_places=3, null=True, blank=True
+    )
+
     def __str__(self):
         return "%s %s" % (self.full_code, self.course.semester)