perf(campaign): batch tenant summaries

tests/test_tenant_summary_batch.py

@@ -0,0 +1,77 @@
+from __future__ import annotations
+
+import unittest
+
+from sqlalchemy import create_engine, event
+from sqlalchemy.orm import Session
+
+from govoplan_access.backend.db.models import Account, Group, User
+from govoplan_campaign.backend.db.models import Campaign
+from govoplan_campaign.backend.manifest import _tenant_summary_batch
+from govoplan_core.core.change_sequence import ChangeSequenceEntry
+from govoplan_core.db.base import Base
+
+
+class CampaignTenantSummaryBatchTests(unittest.TestCase):
+    def test_batch_summary_groups_all_tenants_in_one_query(self) -> None:
+        engine = create_engine("sqlite+pysqlite:///:memory:")
+        Base.metadata.create_all(
+            engine,
+            tables=[
+                Account.__table__,
+                User.__table__,
+                Group.__table__,
+                Campaign.__table__,
+                ChangeSequenceEntry.__table__,
+            ],
+        )
+        try:
+            with Session(engine) as session:
+                session.add_all(
+                    [
+                        Campaign(
+                            id="campaign-1",
+                            tenant_id="tenant-1",
+                            external_id="one",
+                            name="One",
+                        ),
+                        Campaign(
+                            id="campaign-2",
+                            tenant_id="tenant-1",
+                            external_id="two",
+                            name="Two",
+                        ),
+                        Campaign(
+                            id="campaign-3",
+                            tenant_id="tenant-2",
+                            external_id="three",
+                            name="Three",
+                        ),
+                    ]
+                )
+                session.commit()
+                query_count = 0
+
+                def count_query(*_args: object) -> None:
+                    nonlocal query_count
+                    query_count += 1
+
+                event.listen(engine, "before_cursor_execute", count_query)
+                try:
+                    counts = _tenant_summary_batch(
+                        session,
+                        ["tenant-1", "tenant-2", "tenant-empty"],
+                    )
+                finally:
+                    event.remove(engine, "before_cursor_execute", count_query)
+
+            self.assertEqual(1, query_count)
+            self.assertEqual({"campaigns": 2}, counts["tenant-1"])
+            self.assertEqual({"campaigns": 1}, counts["tenant-2"])
+            self.assertNotIn("tenant-empty", counts)
+        finally:
+            engine.dispose()
+
+
+if __name__ == "__main__":
+    unittest.main()