put in some placeholder code for fast deletes

backend/app/db/functions/recommendations_functions.py

@@ -1,5 +1,5 @@
 from tqdm import tqdm
-from sqlalchemy import insert, delete
+from sqlalchemy import insert, delete, text
 from sqlalchemy.orm import Session
 from sqlalchemy.exc import SQLAlchemyError
 from backend.app.db.models.recommendations import (
@@ -175,6 +175,34 @@ def chunked(iterable, size=100):
         yield iterable[i:i + size]
 
 
+def fast_delete_recommendations(session, chunk):
+    values = ",".join(f"({pid})" for pid in chunk)
+
+    sql = text(f"""
+        WITH ids(property_id) AS (
+            VALUES {values}
+        )
+        DELETE FROM recommendation r
+        USING ids
+        WHERE r.property_id = ids.property_id;
+    """)
+
+    session.execute(sql)
+
+    # Note; we may be able to go even faster like this:
+    # def delete_with_temp_table(session, chunk):
+    #     session.execute(text("CREATE TEMP TABLE tmp_ids (id bigint) ON COMMIT DROP;"))
+    #
+    #     insert_sql = "INSERT INTO tmp_ids (id) VALUES " + ",".join(f"({i})" for i in chunk)
+    #     session.execute(text(insert_sql))
+    #
+    #     session.execute(text("""
+    #         DELETE FROM recommendation r
+    #         USING tmp_ids t
+    #         WHERE r.property_id = t.id;
+    #     """))
+
+
 def clear_portfolio(session: Session, portfolio_id: int, batch_size=100):
     # --------------------------
     # Collect IDs up-front
@@ -252,14 +280,11 @@ def clear_portfolio(session: Session, portfolio_id: int, batch_size=100):
     tqdm.write("Deleting Scenarios…")
     session.execute(delete(Scenario).where(Scenario.portfolio_id == portfolio_id))
 
-    # Recommendations
+    # Recommendations - fast delete
     for chunk in tqdm(chunked(property_ids, batch_size),
                       total=(len(property_ids) // batch_size) + 1,
                       desc="Deleting Recommendations"):
-        session.execute(
-            delete(Recommendation)
-            .where(Recommendation.property_id.in_(chunk))
-        )
+        fast_delete_recommendations(session, chunk)
 
     # Inspections
     for chunk in tqdm(chunked(property_ids, batch_size),