/**
 * 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;
  virtual int calc_result2(
      common::ObObj& result, const common::ObObj& name, const common::ObObj& scope, common::ObExprCtx& expr_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 */