fixed N+1 problem on ClassFeatureItems

Author: calumbell

api_v2/migrations/0027_alter_classfeatureitem_parent.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.1.2 on 2025-03-24 14:10
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api_v2', '0026_delete_searchresult'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='classfeatureitem',
+            name='parent',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='feature_items', to='api_v2.classfeature'),
+        ),
+    ]

api_v2/migrations/0028_alter_classfeature_parent.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.1.2 on 2025-03-24 14:14
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api_v2', '0027_alter_classfeatureitem_parent'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='classfeature',
+            name='parent',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='features', to='api_v2.characterclass'),
+        ),
+    ]

api_v2/models/characterclass.py

@@ -23,7 +23,7 @@ class ClassFeatureItem(models.Model):
     # Somewhere in here is where you'd define a field that would eventually display as "Rage Damage +2"
     # Also spell slots...?
 
-    parent = models.ForeignKey('ClassFeature', on_delete=models.CASCADE)
+    parent = models.ForeignKey('ClassFeature', on_delete=models.CASCADE, related_name="feature_items")
     level = models.IntegerField(validators=[MinValueValidator(0),MaxValueValidator(20)])
     detail = models.CharField(
         null=True,
@@ -48,17 +48,16 @@ class ClassFeature(HasName, HasDescription, FromDocument):
     """This class represents an individual class feature, such as Rage, or Extra
     Attack."""
 
-    parent = models.ForeignKey('CharacterClass',
-        on_delete=models.CASCADE)
+    parent = models.ForeignKey('CharacterClass', on_delete=models.CASCADE, related_name="features")
 
     def gained_at(self):
-        return self.classfeatureitem_set.exclude(column_value__isnull=False)
+        return self.feature_items.filter(column_value__isnull=True)
 
     def table_data(self):
         """Returns an array of tabular data relating to the feature. Each
         array element is a table-row of data. Not needed for most features."""
 
-        return self.classfeatureitem_set.exclude(column_value__isnull=True)
+        return self.feature_items.filter(column_value__isnull=False)
 
     # Infer the type of this feature based on the `key`
     @property
@@ -134,11 +133,6 @@ def is_subclass(self):
         """Returns whether the object is a subclass."""
         return self.subclass_of is not None
 
-    @property
-    def features(self):
-        """Returns the set of features that are related to this class."""
-        return self.classfeature_set
-
     @extend_schema_field(serializers.DictField(
         child=inline_serializer(
             name="levels",
@@ -228,7 +222,7 @@ def __str__(self):
     def as_text(self):
         text = self.name + '\n'
 
-        for feature in self.classfeature_set.all():
+        for feature in self.features.all():
             text+='\n' + feature.as_text()
 
         return text

api_v2/serializers/characterclass.py

@@ -16,25 +16,55 @@ class Meta:
 class ClassFeatureColumnItemSerializer(GameContentSerializer):
     class Meta:
         model = models.ClassFeatureItem
-        fields = ['level','column_value']
+        fields = ['level', 'column_value']
+
+class ClassFeaturePrefetchSerializer(GameContentSerializer):
+    class Meta:
+        model = models.ClassFeatureItem
+        fields = ['level', 'detail', 'column_value']
 
 class ClassFeatureSerializer(GameContentSerializer):
     key = serializers.ReadOnlyField()
-    gained_at = ClassFeatureItemSerializer(
-        many=True
-    )
+    feature_items = ClassFeaturePrefetchSerializer(many=True, read_only=True)
+
+    def to_representation(self, instance):
+        # run 'to_representation' on super-class (GameContentSerializer)
+        representation = super().to_representation(instance)
+
+        # Filters non-table data from FeatureItems
+        gained_at = [
+            ClassFeatureItemSerializer(item).data
+            for item in instance.feature_items.all()
+            if item.column_value is None
+        ]
+
+        # Filters table data from FeatureItems
+        column_data = [
+            ClassFeatureColumnItemSerializer(item).data
+            for item in instance.feature_items.all()
+            if item.column_value is not None
+        ]
+
+        # replace 'feature_items' with 'gained_at' and 'column_data' in representation
+        representation['gained_at'] = gained_at
+        representation['column_data'] = column_data
+        del representation['feature_items']
 
-    table_data = ClassFeatureColumnItemSerializer(
-        many=True
-    )
+        return representation
 
     class Meta:
         model = models.ClassFeature
-        fields = ['key', 'name', 'desc','gained_at','table_data', 'feature_type']
+        fields = [
+            'key',
+            'name',
+            'desc',
+            'feature_type',
+            'feature_items'
+        ]
 
 class CharacterClassSerializer(GameContentSerializer):
     key = serializers.ReadOnlyField()
-    features = ClassFeatureSerializer(many=True)
+    features = ClassFeatureSerializer(many=True, read_only=True)
     hit_points = serializers.ReadOnlyField()
     document = DocumentSummarySerializer()
 

api_v2/views/characterclass.py

@@ -33,4 +33,4 @@ class CharacterClassViewSet(EagerLoadingMixin, viewsets.ReadOnlyModelViewSet):
     filterset_class = CharacterClassFilterSet
 
     select_related_fields = []
-    prefetch_related_fields = ['document', 'saving_throws', 'features', 'subclass_of']
+    prefetch_related_fields = ['document', 'saving_throws', 'features', 'subclass_of', 'features__feature_items']