feat: Phase2影响分析 — EXPLAIN预检+大表检测(简化版)+执行策略+风险评估table_sizes支持 (1141测试)

新增:
- explain_preview.py: EXPLAIN预检服务(MySQL/PG), 影响行数预估, 全表扫描检测
- ticket.executor: 三种执行策略(stop_on_error/continue/transaction)
- risk_evaluator: table_sizes参数, 大表ALTER/UPDATE/DELETE自动升级high
- test_phase2_features.py: 22个测试(EXPLAIN+执行策略+大表检测)

简化:
- 砍掉CTX-001上下文感知规则(复杂二次扫描), 合并大表检测到risk_evaluator
- 审核引擎保持纯静态分析, 不再导入_RULE_REGISTRY做二次扫描

模型:
- Ticket加exec_strategy字段
- TicketSqlItem模型
- schema加sql_type/exec_strategy/risk_level/workflow_id

backend/app/services/ticket_executor.py

@@ -220,29 +220,13 @@ class TicketExecutor:
     # ===== MySQL 执行 =====
 
     async def _execute_mysql(self, ticket: Ticket, instance: Instance) -> ExecutionReport:
-        """执行 MySQL 工单。
-
-        执行流程:
-        1. 语法预校验（sqlparse 解析）
-        2. 建立连接（autocommit=False 显式事务）
-        3. 执行前快照和数据备份
-        4. 在事务中执行 SQL
-        5. 执行后验证
-        6. 验证通过则提交，失败则回滚
-        7. 生成报告
-
-        Args:
-            ticket: 工单对象
-            instance: MySQL 实例连接信息
-
-        Returns:
-            ExecutionReport: 执行报告
-        """
+        """执行 MySQL 工单。"""
         import aiomysql
 
         report = ExecutionReport()
         start_time = time.time()
         sql_content = ticket.sql_content.strip()
+        exec_strategy = getattr(ticket, "exec_strategy", "stop_on_error") or "stop_on_error"
 
         # 获取超时配置（从 ticket 或选项中）
         custom_timeout = getattr(ticket, 'options', None) or {}
@@ -279,6 +263,7 @@ class TicketExecutor:
                 total_affected = 0
                 output_lines: List[str] = []
                 execution_failed = False
+                failed_count = 0
 
                 statements = self._split_statements(sql_content)
                 for stmt in statements:
@@ -293,10 +278,15 @@ class TicketExecutor:
                             total_affected += max(0, affected) if affected is not None else 0
                             output_lines.append(f"[{stmt[:50]}...] 影响 {affected} 行")
                     except Exception as stmt_error:
+                        failed_count += 1
                         execution_failed = True
                         output_lines.append(f"[{stmt[:50]}...] 执行失败: {stmt_error}")
                         report.errors.append(f"语句执行失败: {stmt_error}")
-                        break
+
+                        if exec_strategy == "stop_on_error":
+                            break
+                        # continue: 跳过失败继续执行
+                        # transaction: 任何失败都回滚（默认行为，break 后走 rollback）
 
                 report.affected_rows = total_affected
                 report.raw_output = "\n".join(output_lines)
@@ -311,8 +301,14 @@ class TicketExecutor:
                     sql_content, report
                 )
 
-                # 事务决策：验证通过且无执行错误则提交，否则回滚
-                if not execution_failed and report.validation_passed:
+                # 事务决策：根据执行策略处理
+                if exec_strategy == "continue" and failed_count > 0 and failed_count < len(statements):
+                    # continue 模式：部分失败也算成功，提交已执行的语句
+                    await conn.commit()
+                    report.status = "partial_success"
+                    report.errors.insert(0, f"部分失败: {failed_count}/{len(statements)} 条语句失败")
+                    logger.warning("工单 %d MySQL 部分执行成功: %d 条失败", ticket.id, failed_count)
+                elif not execution_failed and report.validation_passed:
                     await conn.commit()
                     report.status = "success"
                     logger.info("工单 %d MySQL 执行成功，事务已提交", ticket.id)