去除alter外键约束时ob_ddl_timeout的约束，修改当前代码中遗失返回码和dead code的问题 (#344)

* 去除alter外键约束时ob_ddl_timeout的约束，修改遗失返回码和dead code的问题

* 修改log记录的信息，修改移除dead code的代码

src/sql/code_generator/ob_expr_generator_impl.cpp

@@ -956,12 +956,8 @@ int ObExprGeneratorImpl::visit_enum_set_expr(ObNonTerminalRawExpr& expr, ObExprT
     LOG_WARN("invalid old op", K(expr), K(ret));
   } else {
     ObExprTypeToStr* type_to_str = static_cast<ObExprTypeToStr*>(old_op);
-    if (OB_ISNULL(type_to_str)) {
-      ret = OB_ERR_UNEXPECTED;
-      LOG_WARN("failed to static cast ObExprOperator * to ObExprTypeToStr *", K(expr), K(ret));
-    } else if (OB_FAIL(enum_set_op->deep_copy_str_values(type_to_str->get_str_values()))) {
+    if (OB_FAIL(enum_set_op->deep_copy_str_values(type_to_str->get_str_values()))) {
       LOG_WARN("failed to deep_copy_str_values", K(expr), K(ret));
-    } else { /*do nothing*/
     }
   }
   return ret;

src/sql/engine/cmd/ob_table_executor.cpp

@@ -1742,6 +1742,8 @@ int ObAlterTableExecutor::check_fk_constraint_data_validity(ObExecContext& ctx,
   const ObString& origin_database_name = alter_table_schema.get_origin_database_name();
   const ObString& origin_table_name = alter_table_schema.get_origin_table_name();
   const ObTableSchema* orig_table_schema = NULL;
+  THIS_WORKER.set_timeout_ts(ObTimeUtility::current_time() + OB_MAX_USER_SPECIFIED_TIMEOUT);
+  const int64_t start_time = ObTimeUtility::current_time();
 
   if (OB_ISNULL(gctx.schema_service_)) {
     ret = OB_ERR_UNEXPECTED;
@@ -1777,6 +1779,9 @@ int ObAlterTableExecutor::check_fk_constraint_data_validity(ObExecContext& ctx,
       LOG_WARN("fail to check data validity by inner sql", K(ret));
     }
   }
+  
+  const int64_t end_time = ObTimeUtility::current_time();
+  LOG_DEBUG("elapsed time for check_fk_constraint_data_validity:", K(start_time), K(end_time), K(end_time-start_time));
   return ret;
 }
 

src/sql/resolver/ddl/ob_create_func_resolver.cpp

@@ -53,9 +53,10 @@ int ObCreateFuncResolver::resolve(const ParseNode& parse_tree)
     }
 
     ObObj plugin_path;
-    session_info_->get_sys_variable(SYS_VAR_PLUGIN_DIR, plugin_path);
     ObString plugin_path_str;
-    if (OB_FAIL(plugin_path.get_string(plugin_path_str))) {
+    if (OB_FAIL(session_info_->get_sys_variable(SYS_VAR_PLUGIN_DIR, plugin_path))) {
+      LOG_WARN("get sys variable failed", K(ret));
+    } else if (OB_FAIL(plugin_path.get_string(plugin_path_str))) {
       LOG_WARN("get plugin path failed", K(ret));
     } else {
       create_func_arg.udf_.set_name(