/**
 * Copyright (c) 2021 OceanBase
 * OceanBase CE is licensed under Mulan PubL v2.
 * You can use this software according to the terms and conditions of the Mulan PubL v2.
 * You may obtain a copy of Mulan PubL v2 at:
 *          http://license.coscl.org.cn/MulanPubL-2.0
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PubL v2 for more details.
 */

#ifndef _OB_EXPR_GET_SYS_VAR_H
#define _OB_EXPR_GET_SYS_VAR_H 1
#include "sql/engine/expr/ob_expr_operator.h"
#include "sql/session/ob_sql_session_info.h"

namespace oceanbase
{
namespace sql
{
// get_sys_var(name, scope)
class ObExprGetSysVar: public ObFuncExprOperator
{
public:
  static const ObExprOperatorType op_type_;
  ObExprGetSysVar();
  explicit  ObExprGetSysVar(common::ObIAllocator &alloc);
  virtual ~ObExprGetSysVar();
  virtual int calc_result_type2(ObExprResType &type,
                                ObExprResType &type1,
                                ObExprResType &type2,
                                common::ObExprTypeCtx &type_ctx) const;
  // for engine 3.0
  virtual int cg_expr(ObExprCGCtx &expr_cg_ctx, const ObRawExpr &raw_expr,
                       ObExpr &rt_expr) const override;
  static int calc_get_sys_val_expr(const ObExpr &expr, ObEvalCtx &ctx,
                                 ObDatum &res_datum);
private:
  static int calc_(common::ObObj &result, const common::ObString &var_name, 
                   const int64_t var_scope, ObSQLSessionInfo *session, 
                   ObExecContext *exec_ctx, common::ObIAllocator &alloc);
  static int get_session_var(common::ObObj &result, const common::ObString &var_name,
                             common::ObIAllocator &alloc, ObSQLSessionInfo *session, 
                             ObExecContext *exec_ctx);
  static int get_sys_var_disp_obj(common::ObIAllocator &allocator,
                           const ObSQLSessionInfo &session,
                           const common::ObString &var_name,
                           common::ObObj &disp_obj);
private:
  // disallow copy
  DISALLOW_COPY_AND_ASSIGN(ObExprGetSysVar);
};

} // end namespace sql
} // end namespace oceanbase

#endif /* _OB_EXPR_GET_SYS_VAR_H */