Fix comparison pipeline event and transaction handling

site/db/connection.py

@@ -10,12 +10,29 @@ import sqlite3
 import threading
 import time
 import os
+from contextlib import contextmanager
 
 DB_PATH = "/tmp/contracts.db"
 _db_session_key = None
 _local = threading.local()
 
 
+@contextmanager
+def transaction():
+    """Run DB writes atomically on the current thread connection."""
+    conn = get_conn()
+    conn.execute("BEGIN IMMEDIATE")
+    _local.in_transaction = True
+    try:
+        yield conn
+        conn.commit()
+    except Exception:
+        conn.rollback()
+        raise
+    finally:
+        _local.in_transaction = False
+
+
 def init_db():
     """Создать/пересоздать БД + схему. Вызывается при старте и после cleanup."""
     global _db_session_key
@@ -171,7 +188,8 @@ def execute(sql, params=None):
     conn = get_conn()
     sql = _pg_to_sqlite(sql)
     cur = conn.execute(sql, params or [])
-    conn.commit()
+    if not getattr(_local, "in_transaction", False):
+        conn.commit()
     return cur.rowcount