From 9c48eb20c5167fc9ce4a5abb6c837c2bee749050 Mon Sep 17 00:00:00 2001
From: Dennis Thiessen <dennis@thiessen.io>
Date: Fri, 25 Sep 2026 13:17:51 +0200
Subject: [PATCH] Fix backtest benchmark read after optional table probe

---
 app/services/backtest_service.py    |  9 ++++++---
 tests/unit/test_backtest_service.py | 26 ++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/app/services/backtest_service.py b/app/services/backtest_service.py
index 93ce5a8..777f23a 100644
--- a/app/services/backtest_service.py
+++ b/app/services/backtest_service.py
@@ -937,13 +937,16 @@ async def _load_research_rank_only_symbols(db: AsyncSession) -> set[str]:
     """Symbols that feed signal IC only (no GTL/candidate replay).
 
     Optional side table ``research_rank_only`` on research snapshots. Missing
-    table → empty set (production path unchanged).
+    table → empty set (production path unchanged). Probe within a savepoint:
+    PostgreSQL aborts the current transaction after a missing-table error, so
+    catching that error alone would break the subsequent benchmark read.
     """
     from sqlalchemy import text
 
     try:
-        result = await db.execute(text("SELECT symbol FROM research_rank_only"))
-        return {str(row[0]).upper() for row in result.fetchall() if row[0]}
+        async with db.begin_nested():
+            result = await db.execute(text("SELECT symbol FROM research_rank_only"))
+            return {str(row[0]).upper() for row in result.fetchall() if row[0]}
     except Exception:
         return set()
 
diff --git a/tests/unit/test_backtest_service.py b/tests/unit/test_backtest_service.py
index 391d84e..fab3100 100644
--- a/tests/unit/test_backtest_service.py
+++ b/tests/unit/test_backtest_service.py
@@ -9,9 +9,11 @@ from types import SimpleNamespace
 
 import pytest
 
+from app.models.benchmark_price import BenchmarkPrice
 from app.models.ohlcv import OHLCVRecord
 from app.models.ticker import Ticker
 from app.services import backtest_service as bt
+from app.services.benchmark_service import load_benchmark_closes
 from app.services.outcome_service import (
     OUTCOME_EXPIRED,
     OUTCOME_STOP_HIT,
@@ -1600,6 +1602,30 @@ def _pin_benchmark(monkeypatch, closes: dict | None = None) -> None:
     monkeypatch.setattr(bt, "_load_benchmark_closes_for_backtest", _stub)
 
 
+async def test_missing_research_table_does_not_abort_benchmark_read(session, monkeypatch):
+    """The optional research table is absent online; its failed probe must be
+    isolated so PostgreSQL can still read the SPY prices in the same session.
+    """
+    close_date = date(2025, 1, 2)
+    session.add(BenchmarkPrice(symbol="SPY", date=close_date, close=470.0))
+    await session.commit()
+
+    real_execute = session.execute
+    probed_in_savepoint = False
+
+    async def track_probe(statement, *args, **kwargs):
+        nonlocal probed_in_savepoint
+        if str(statement) == "SELECT symbol FROM research_rank_only":
+            probed_in_savepoint = session.in_nested_transaction()
+        return await real_execute(statement, *args, **kwargs)
+
+    monkeypatch.setattr(session, "execute", track_probe)
+
+    assert await bt._load_research_rank_only_symbols(session) == set()
+    assert probed_in_savepoint
+    assert await load_benchmark_closes(session) == {close_date: 470.0}
+
+
 async def _seed_oscillating_ticker(session, symbol: str, n: int = 160) -> None:
     t = Ticker(symbol=symbol)
     session.add(t)