Improve transaction management and connection cleanup in incremental sync

- Add explicit BEGIN TRANSACTION for clear transaction boundaries
- Ensure IDENTITY_INSERT state is properly tracked and cleaned up
- Add finally block to guarantee Access connection cleanup
- Move table existence check inside sync loop for better scope

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

run_incremental_sync.py

@@ -113,6 +113,7 @@ def process_sync_task():
                 log_error(f"无法访问文件: {clean_path}")
                 continue
 
+            acc_conn = None
             try:
                 acc_conn = db_utils.get_access_conn(clean_path)
                 acc_cursor = acc_conn.cursor()
@@ -139,7 +140,25 @@ def process_sync_task():
 
                 log_processing(f"正在同步表 [{acc_table}] → [{target_table}] ({len(record_ids)} 条记录)")
 
+                # 检查目标表是否存在，不存在则自动创建
+                if not db_utils.table_exists(sql_cursor, target_schema, target_table):
+                    db_utils.ensure_schema(sql_cursor, target_schema)
+                    acc_cursor.execute(f"SELECT TOP 1 * FROM [{acc_table}]")
+                    db_utils.create_table_from_access(
+                        sql_cursor, target_schema, target_table,
+                        acc_cursor.description, pk_col
+                    )
+                    log_info(f"目标表 [{target_table}] 不存在，已自动创建")
+
+                # 事务状态追踪
+                identity_enabled = False
+                transaction_begun = False
+
                 try:
+                    # --- 开始事务 ---
+                    sql_cursor.execute("BEGIN TRANSACTION")
+                    transaction_begun = True
+
                     # --- A. Access 查新数据 ---
                     ids_placeholders = ','.join(['?'] * len(record_ids))
                     acc_sql = f"SELECT * FROM [{acc_table}] WHERE [{pk_col}] IN ({ids_placeholders})"
@@ -147,35 +166,28 @@ def process_sync_task():
                     new_rows = acc_cursor.fetchall()
                     acc_cols = [col[0] for col in acc_cursor.description]
 
-                    # --- B. SQL Server 删旧插新 (事务) ---
+                    # --- B. SQL Server 删旧插新 ---
-                    # 1. 删除
+                    # 1. 删除旧数据
                     del_sql = f"DELETE FROM {target_full_name} WHERE [{pk_col}] IN ({ids_placeholders})"
                     sql_cursor.execute(del_sql, record_ids)
 
-                    # 2. 插入
+                    # 2. 插入新数据
                     if new_rows:
                         insert_sql = db_utils.generate_insert_sql(target_schema, target_table, acc_cols)
 
                         # 检查并启用 IDENTITY_INSERT
                         has_identity = has_identity_column(sql_cursor, target_schema, target_table)
-                        identity_enabled = False
 
                         if has_identity:
-                            try:
                             sql_cursor.execute(f"SET IDENTITY_INSERT {target_full_name} ON")
                             identity_enabled = True
-                            except Exception as id_err:
-                                log_error(f"无法启用 IDENTITY_INSERT: {id_err}")
-                                raise
 
                         sql_cursor.executemany(insert_sql, new_rows)
 
                         # 关闭 IDENTITY_INSERT
                         if identity_enabled:
-                            try:
                             sql_cursor.execute(f"SET IDENTITY_INSERT {target_full_name} OFF")
-                            except Exception as id_err:
+                            identity_enabled = False
-                                log_warning(f"关闭 IDENTITY_INSERT 时警告: {id_err}")
 
                     # 3. 标记日志 Synced = 1
                     log_placeholders = ','.join(['?'] * len(log_ids))
@@ -186,23 +198,38 @@ def process_sync_task():
                     """
                     sql_cursor.execute(update_log_sql, log_ids)
 
+                    # 提交事务
                     sql_conn.commit()
+                    transaction_begun = False
                     log_info(f"表 [{target_table}] 同步完成: {len(record_ids)} 条记录")
 
                     file_success_count += 1
                     file_total_records += len(record_ids)
 
                 except Exception as tbl_err:
-                    # 确保清理 IDENTITY_INSERT 状态
+                    # 回滚事务
+                    if transaction_begun:
+                        sql_conn.rollback()
+                        transaction_begun = False
+
+                    # 清理 IDENTITY_INSERT 状态
+                    if identity_enabled:
                         try:
                             sql_cursor.execute(f"SET IDENTITY_INSERT {target_full_name} OFF")
                         except:
                             pass
+
                     log_error(f"表 [{acc_table}] 同步失败: {tbl_err}")
-                    sql_conn.rollback()
                     file_error_count += 1
 
-            acc_conn.close() # 关闭 Access 连接
+            finally:
+                # 确保 Access 连接关闭
+                try:
+                    if acc_conn:
+                        acc_conn.close()
+                        log_info(f"已关闭 Access 连接: {os.path.basename(clean_path)}")
+                except Exception as close_err:
+                    log_warning(f"关闭 Access 连接时出错: {close_err}")
             
             # 输出文件级别的汇总
             if file_success_count > 0 or file_error_count > 0: