[back] feat: add a dedicated route for random reco.

backend/tournesol/serializers/poll.py

@@ -123,3 +123,9 @@ class RecommendationsFilterSerializer(serializers.Serializer):
         help_text="If true and a user is authenticated, then entities compared by the"
         " user will be removed from the response",
     )
+
+
+class RecommendationsRandomFilterSerializer(serializers.Serializer):
+    random = serializers.IntegerField(default=None)
+    date_lte = serializers.DateTimeField(default=None)
+    date_gte = serializers.DateTimeField(default=None)

backend/tournesol/urls.py

@@ -28,6 +28,7 @@
     PollsRecommendationsView,
     PollsView,
 )
+from .views.polls_reco_random import RandomRecommendationList
 from .views.previews import (
     DynamicWebsitePreviewComparison,
     DynamicWebsitePreviewDefault,
@@ -196,6 +197,11 @@
         PollsRecommendationsView.as_view(),
         name="polls_recommendations",
     ),
+    path(
+        "polls/<str:name>/recommendations/random/",
+        RandomRecommendationList.as_view(),
+        name="polls_recommendations_random",
+    ),
     path(
         "polls/<str:name>/entities/<str:uid>",
         PollsEntityView.as_view(),

backend/tournesol/utils/constants.py

@@ -18,4 +18,5 @@
 COMPARISON_MAX = 10.0
 
 # Default weight for a criteria in the recommendations
+# FIXME: the default weight used by the front end is 50, not 10
 CRITERIA_DEFAULT_WEIGHT = 10

backend/tournesol/views/polls.py

@@ -298,6 +298,13 @@ def annotate_and_prefetch_scores(self, queryset, request, poll: Poll):
         criteria_weight = self._build_criteria_weight_condition(
             request, poll, when="all_criteria_scores__criteria"
         )
+
+        # FIXME: we can significantly improve the performance of the queryset
+        # by filtering the criteria on their names, to remove those that are
+        # not present in the request.
+        #
+        #   ex:
+        #       all_criteria_scores__criteria__in=[...]
         queryset = queryset.filter(
             all_criteria_scores__poll=poll,
             all_criteria_scores__score_mode=score_mode,

backend/tournesol/views/polls_reco_random.py

@@ -0,0 +1,81 @@
+from django.utils.decorators import method_decorator
+from drf_spectacular.types import OpenApiTypes
+from drf_spectacular.utils import (
+    OpenApiExample,
+    OpenApiParameter,
+    extend_schema,
+    extend_schema_view,
+)
+
+from tournesol.models import Entity
+from tournesol.serializers.entity import EntityNoExtraFieldSerializer
+from tournesol.serializers.poll import RecommendationsRandomFilterSerializer
+from tournesol.utils.cache import cache_page_no_i18n
+from tournesol.views import PollRecommendationsBaseAPIView
+
+
+class RandomRecommendationBaseAPIView(PollRecommendationsBaseAPIView):
+    def get_queryset(self):
+        """
+        Return a queryset of random recommended entities.
+
+        This queryset is designed to be more performant than the queryset
+        of the regular recommendations view. For this reason, it doesn't allow
+        to:
+            - filter entities by text
+            - filter entities by weighted criteria score
+            - or anything involving a SQL JOIN on EntityCriteriaScore
+        """
+        poll = self.poll_from_url
+        queryset = Entity.objects.all()
+        queryset, _ = self.filter_by_parameters(self.request, queryset, poll)
+        queryset = queryset.with_prefetched_poll_ratings(poll_name=poll.name)
+        queryset = queryset.filter_safe_for_poll(poll)
+        queryset = queryset.order_by("?")
+        return queryset
+
+
+@extend_schema_view(
+    get=extend_schema(
+        parameters=[
+            RecommendationsRandomFilterSerializer,
+            OpenApiParameter(
+                "metadata",
+                OpenApiTypes.OBJECT,
+                style="deepObject",
+                description="Filter by one or more metadata.",
+                examples=[
+                    OpenApiExample(
+                        name="No metadata filter",
+                    ),
+                    OpenApiExample(
+                        name="Videos - some examples",
+                        value={"language": ["en", "pt"], "uploader": "Kurzgesagt – In a Nutshell"},
+                    ),
+                    OpenApiExample(
+                        name="Videos - videos of 8 minutes or less (480 sec)",
+                        value={"duration:lte:int": "480"},
+                    ),
+                    OpenApiExample(
+                        name="Candidates - some examples",
+                        value={
+                            "name": "A candidate full name",
+                            "youtube_channel_id": "channel ID",
+                        },
+                    ),
+                ],
+            ),
+        ],
+    )
+)
+class RandomRecommendationList(RandomRecommendationBaseAPIView):
+    """
+    Return a random list of recommended entities.
+    """
+    permission_classes = []
+    serializer_class = EntityNoExtraFieldSerializer
+    poll_parameter = "name"
+
+    @method_decorator(cache_page_no_i18n(60 * 10))  # 10 minutes cache
+    def get(self, request, *args, **kwargs):
+        return self.list(request, *args, **kwargs)