From 46ca714ef992726a95e6b2a6e6aed85726ab399e Mon Sep 17 00:00:00 2001
From: Daniel Roth <daniel_roth@hotmail.co.uk>
Date: Mon, 29 Jun 2026 15:06:47 +0000
Subject: [PATCH] =?UTF-8?q?Batch=20plan=20saves=20reduce=20RDS=20CPU=20dur?=
 =?UTF-8?q?ing=20bulk=20modelling=20runs=20=F0=9F=9F=A9?=
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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 repositories/plan/plan_postgres_repository.py | 75 ++++++++++++++++++-
 .../repositories/plan/test_plan_batch_save.py |  2 +-
 2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/repositories/plan/plan_postgres_repository.py b/repositories/plan/plan_postgres_repository.py
index 36253764..9bf22aea 100644
--- a/repositories/plan/plan_postgres_repository.py
+++ b/repositories/plan/plan_postgres_repository.py
@@ -1,5 +1,8 @@
 from __future__ import annotations
 
+from typing import Any
+
+from sqlalchemy import insert as _sa_insert
 from sqlmodel import Session, col, update
 
 from domain.modelling.plan import Plan
@@ -7,6 +10,15 @@ from infrastructure.postgres.modelling import PlanModel, RecommendationModel
 from repositories.plan.plan_repository import PlanRepository, PlanSaveRequest
 
 
+def _col_values(model: Any, exclude: frozenset[str] = frozenset()) -> dict[str, Any]:
+    """Extract column-keyed values from a SQLModel instance for Core INSERT."""
+    return {
+        c.name: getattr(model, c.name)
+        for c in model.__table__.c
+        if c.name not in exclude
+    }
+
+
 class PlanPostgresRepository(PlanRepository):
     """Maps a Plan and its Plan Measures onto the live ``plan`` /
     ``recommendation`` tables (ADR-0017). Does not commit — the Unit of Work
@@ -65,4 +77,65 @@ class PlanPostgresRepository(PlanRepository):
         return plan_row.id
 
     def save_batch(self, requests: list[PlanSaveRequest]) -> list[int]:
-        raise NotImplementedError
+        """Persist all Plans in three statements regardless of batch size.
+
+        1. One demote UPDATE (only when any request has ``is_default=True``).
+        2. One bulk plan INSERT with RETURNING to capture ids positionally.
+        3. One bulk recommendation INSERT (skipped when no measures exist).
+        """
+        if not requests:
+            return []
+
+        # Demote prior default Plans for every property in the batch that is
+        # receiving a new default Plan — one UPDATE for the whole batch.
+        default_pids = [r.property_id for r in requests if r.is_default]
+        if default_pids:
+            # scenario_id is uniform per batch (one scenario per SQS message).
+            scenario_id = requests[0].scenario_id
+            self._session.exec(  # type: ignore[call-overload]
+                update(PlanModel)
+                .where(
+                    col(PlanModel.property_id).in_(default_pids),
+                    col(PlanModel.scenario_id) == scenario_id,
+                )
+                .values(is_default=False)
+            )
+
+        # Bulk INSERT all plan rows; capture returned ids positionally.
+        plan_rows = [
+            _col_values(
+                PlanModel.from_domain(
+                    r.plan,
+                    property_id=r.property_id,
+                    scenario_id=r.scenario_id,
+                    portfolio_id=r.portfolio_id,
+                    is_default=r.is_default,
+                ),
+                exclude=frozenset({"id"}),
+            )
+            for r in requests
+        ]
+        returned = self._session.execute(  # type: ignore[deprecated]
+            _sa_insert(PlanModel).returning(PlanModel.__table__.c["id"]),  # type: ignore[attr-defined]
+            plan_rows,
+        ).all()
+        plan_ids = [row[0] for row in returned]
+
+        # Accumulate recommendation rows across all requests; properties with
+        # zero measures contribute nothing (no special-casing needed).
+        rec_rows = [
+            _col_values(
+                RecommendationModel.from_domain(
+                    measure, property_id=r.property_id, plan_id=plan_id
+                ),
+                exclude=frozenset({"id"}),
+            )
+            for r, plan_id in zip(requests, plan_ids)
+            for measure in r.plan.measures
+        ]
+        if rec_rows:
+            self._session.execute(  # type: ignore[deprecated]
+                _sa_insert(RecommendationModel), rec_rows
+            )
+
+        return plan_ids
diff --git a/tests/repositories/plan/test_plan_batch_save.py b/tests/repositories/plan/test_plan_batch_save.py
index e82d0f1e..400b2cdf 100644
--- a/tests/repositories/plan/test_plan_batch_save.py
+++ b/tests/repositories/plan/test_plan_batch_save.py
@@ -86,7 +86,7 @@ def test_single_request_save_batch_matches_save(db_engine: Engine) -> None:
     assert recs_save[0].type == recs_batch[0].type
     assert recs_save[0].estimated_cost == recs_batch[0].estimated_cost
     assert recs_save[0].sap_points == recs_batch[0].sap_points
-    assert recs_save[0].plan_id == batch_id
+    assert recs_batch[0].plan_id == batch_id
 
 
 # ---------------------------------------------------------------------------