OpenConceptLab/ocl_online#456 | Load a page's concept mappings once for includeMappings concept lists

core/common/serializers.py

@@ -262,6 +262,9 @@ def to_representation(self, data):
         self.child.Meta.model.load_list_fields(
             instances, self.child.fields.keys(), get_collection_in_scope(self.context),
             get(self.context, 'request.user') or get(self.context, 'user'))
+        preload_page = getattr(self.child, 'preload_page', None)
+        if preload_page:
+            preload_page(instances)
         return super().to_representation(instances)
 
 

core/concepts/serializers.py

@@ -1,3 +1,4 @@
+from django.db.models import F
 from pydash import get, compact
 from rest_framework.fields import CharField, DateTimeField, BooleanField, URLField, JSONField, SerializerMethodField, \
     UUIDField, ListField, IntegerField, ReadOnlyField
@@ -234,10 +235,52 @@ def get_references(self, obj):
             return obj.collection_references_uris(collection)
         return None
 
-    def get_mappings(self, obj):
+    def mapping_serializer_class(self):
+        from core.mappings.serializers import MappingDetailSerializer, MappingMinimalSerializer
+        request = get(self, 'context.request')
+        is_mapping_brief = request.query_params.get('mappingBrief', None) in TRUTHY
+        return MappingMinimalSerializer if is_mapping_brief else MappingDetailSerializer
+
+    def preloads_direct_mappings(self):
+        return 'mappings' in self.fields and self.include_direct_mappings and not (
+            self.include_indirect_mappings or 'collection' in self.view_kwargs)
+
+    def preload_page(self, instances):
+        """Loads the direct mappings of a whole page of concepts in one go, instead of per concept."""
+        request = get(self, 'context.request')
+        if not (instances and request and self.preloads_direct_mappings()):
+            return
+        from core.mappings.models import Mapping
+        params = request.query_params
+        concept_ids = {
+            concept.id: set(compact([
+                concept.id, concept.versioned_object_id, get(concept.get_latest_version(), 'id')]))
+            for concept in instances
+        }
+        mappings = Mapping.objects.filter(
+            parent_id__in={concept.parent_id for concept in instances},
+            from_concept_id__in=set().union(*concept_ids.values()), id=F('versioned_object_id'))
+        if map_types := compact((params.get('mapTypes', '') or '').split(',')):
+            mappings = mappings.filter(map_type__in=map_types)
+        if target_repo_urls := compact((params.get('targetRepoUrls', '') or '').split(',')):
+            mappings = mappings.filter(to_source_url__in=target_repo_urls)
+        if params.get(INCLUDE_RETIRED_PARAM, None) not in TRUTHY:
+            mappings = mappings.filter(retired=False)
+        mappings = list(mappings.order_by('id'))
+        Mapping.load_list_fields(mappings, self.mapping_serializer_class()().fields.keys(), None, request.user)
+        for concept in instances:
+            concept._preloaded_mappings = [  # pylint: disable=protected-access
+                mapping for mapping in mappings
+                if mapping.parent_id == concept.parent_id and mapping.from_concept_id in concept_ids[concept.id]]
+
+    def get_mappings(self, obj):  # pylint: disable=too-many-locals
         from core.mappings.serializers import MappingDetailSerializer, MappingMinimalSerializer
         context = get(self, 'context')
         request = get(context, 'request')
+        preloaded = getattr(obj, '_preloaded_mappings', None)
+        if preloaded is not None and self.preloads_direct_mappings():
+            child = self.mapping_serializer_class()()
+            return [child.to_representation(mapping) for mapping in preloaded]
         is_mapping_brief = request.query_params.get('mappingBrief', None) in TRUTHY
         map_types = compact((request.query_params.get('mapTypes', '') or '').split(','))
         target_repo_urls = compact((request.query_params.get('targetRepoUrls', '') or '').split(','))

core/concepts/tests/tests.py

@@ -6,7 +6,8 @@
 from elasticsearch_dsl.utils import AttrDict
 from django.contrib.auth.models import Group
 from django.core.exceptions import ValidationError
-from django.db import IntegrityError
+from django.db import IntegrityError, connection
+from django.test.utils import CaptureQueriesContext
 from django.http import Http404, QueryDict
 from django.test import override_settings
 from pydash import omit
@@ -3116,6 +3117,25 @@ def test_get_mappings_direct_with_map_types_and_target_repo_urls_filters(self):
         result = serializer.get_mappings(concept1)
         self.assertEqual(result, [])
 
+    def test_list_serializer_loads_page_mappings_once(self):
+        source = OrganizationSourceFactory()
+        concepts = [ConceptFactory(parent=source) for _ in range(6)]
+        for concept in concepts[:5]:
+            MappingFactory(from_concept=concept, to_concept=concepts[5], parent=source, map_type='Same As')
+            MappingFactory(from_concept=concept, to_concept=concepts[5], parent=source, map_type='Other')
+        query = 'includeMappings=true&mapTypes=Same As,Other'
+        context = self.build_context(query)
+
+        rows = [ConceptListSerializer(concept, context=context).data['mappings'] for concept in concepts]
+        with CaptureQueriesContext(connection) as small:
+            page = ConceptListSerializer(concepts[:2], many=True, context=context).data
+        with CaptureQueriesContext(connection) as large:
+            page = ConceptListSerializer(concepts, many=True, context=context).data
+
+        self.assertEqual([row['mappings'] for row in page], rows)
+        self.assertEqual(len(rows[0]), 2)
+        self.assertLess(len(large) - len(small), 4 * 4)
+
     def test_get_mappings_returns_empty_list_by_default(self):
         concept = ConceptFactory()
         serializer = ConceptListSerializer(context=self.build_context())