refactor: replace broad except blocks with specific exceptions and logger

backend/app/database/connection.py

@@ -2,6 +2,9 @@
 from contextlib import contextmanager
 from typing import Generator
 from app.config.settings import DATABASE_PATH
+from app.logging.setup_logging import get_logger
+
+logger = get_logger(__name__)
 
 
 @contextmanager
@@ -25,7 +28,8 @@ def get_db_connection() -> Generator[sqlite3.Connection, None, None]:
     try:
         yield conn
         conn.commit()
-    except Exception:
+    except Exception as e:
+        logger.error(f"Database transaction failed, rolling back: {e}")
         conn.rollback()
         raise
     finally:

backend/app/database/face_clusters.py

@@ -1,6 +1,9 @@
 import sqlite3
 from typing import Optional, List, Dict, TypedDict, Union
 from app.config.settings import DATABASE_PATH
+from app.logging.setup_logging import get_logger
+
+logger = get_logger(__name__)
 
 # Type definitions
 ClusterId = str
@@ -60,10 +63,10 @@ def db_delete_all_clusters(cursor: Optional[sqlite3.Cursor] = None) -> int:
         if own_connection:
             conn.commit()
         return deleted_count
-    except Exception:
+    except sqlite3.Error as e:
         if own_connection:
             conn.rollback()
-        print("Error deleting all clusters.")
+        logger.error(f"Error deleting all clusters: {e}")
         raise
     finally:
         if own_connection:
@@ -114,9 +117,10 @@ def db_insert_clusters_batch(
         if own_connection:
             conn.commit()
         return cluster_ids
-    except Exception:
+    except sqlite3.Error as e:
         if own_connection:
             conn.rollback()
+        logger.error(f"Error inserting clusters batch: {e}")
         raise
     finally:
         if own_connection:

backend/app/database/faces.py

@@ -3,6 +3,9 @@
 import numpy as np
 from typing import Optional, List, Dict, Union, TypedDict
 from app.config.settings import DATABASE_PATH
+from app.logging.setup_logging import get_logger
+
+logger = get_logger(__name__)
 
 # Type definitions
 FaceId = int
@@ -312,14 +315,22 @@ def db_update_face_cluster_ids_batch(
         conn = sqlite3.connect(DATABASE_PATH)
         cursor = conn.cursor()
 
+    # 1. Prepare update data outside the DB transaction.
+    # mapping.get() calls could raise AttributeError if mappings are malformed;
+    # these are not sqlite3 errors and must be caught before the transaction.
     try:
-        # Prepare update data as tuples (cluster_id, face_id)
-        update_data = []
-        for mapping in face_cluster_mapping:
-            face_id = mapping.get("face_id")
-            cluster_id = mapping.get("cluster_id")
-            update_data.append((cluster_id, face_id))
+        update_data = [
+            (mapping.get("cluster_id"), mapping.get("face_id"))
+            for mapping in face_cluster_mapping
+        ]
+    except (AttributeError, KeyError, TypeError) as e:
+        if own_connection:
+            conn.close()
+        logger.error(f"Failed to prepare face cluster update data: {e}")
+        raise
 
+    # 2. Database transaction — only pure DB operations here, so sqlite3.Error is safe.
+    try:
         cursor.executemany(
             """
             UPDATE faces 
@@ -331,10 +342,10 @@ def db_update_face_cluster_ids_batch(
 
         if own_connection:
             conn.commit()
-    except Exception:
+    except sqlite3.Error as e:
         if own_connection:
             conn.rollback()
-        print("Error updating face cluster IDs in batch.")
+        logger.error(f"Error updating face cluster IDs in batch: {e}")
         raise
     finally:
         if own_connection:

backend/app/database/metadata.py

@@ -3,6 +3,9 @@
 import json
 from typing import Optional, Dict, Any
 from app.config.settings import DATABASE_PATH
+from app.logging.setup_logging import get_logger
+
+logger = get_logger(__name__)
 
 
 def db_create_metadata_table() -> None:
@@ -68,13 +71,23 @@ def db_update_metadata(
     Returns:
         True if the metadata was updated, False otherwise
     """
+    # 1. Prepare/serialize data outside the DB transaction.
+    # json.dumps can raise TypeError/ValueError for non-serializable objects;
+    # these are not sqlite3 errors and must be caught separately.
+    try:
+        metadata_json = json.dumps(metadata)
+    except (TypeError, ValueError) as e:
+        logger.error(f"Failed to serialize metadata: {e}")
+        raise
+
     own_connection = cursor is None
-    if own_connection:
-        conn = sqlite3.connect(DATABASE_PATH)
-        cursor = conn.cursor()
+    conn = None
 
+    # 2. Database transaction / owned connection setup.
     try:
-        metadata_json = json.dumps(metadata)
+        if own_connection:
+            conn = sqlite3.connect(DATABASE_PATH)
+            cursor = conn.cursor()
 
         # Delete all existing rows and insert new one
         cursor.execute("DELETE FROM metadata")
@@ -84,12 +97,12 @@ def db_update_metadata(
         if own_connection:
             conn.commit()
         return success
-    except Exception as e:
+    except sqlite3.Error as e:
         if own_connection:
-            conn.rollback()
-
-        print(f"Error updating metadata: {e}")
+            if conn is not None:
+                conn.rollback()
+        logger.error(f"Error updating metadata: {e}")
         raise
     finally:
-        if own_connection:
+        if own_connection and conn is not None:
             conn.close()