text: --  @testpoint:opengauss关键字distinct(保留)，作为函数名
  
  --关键字不带引号-失败
  drop function if exists distinct;
  create function distinct(i integer)
  returns integer
  as $$
  begin
      return i+1;
  end;
  $$ language plpgsql;
  /
  
  --关键字带双引号-成功
  drop function if exists "distinct";
  create function "distinct"(i integer)
  returns integer
  as $$
  begin
      return i+1;
  end;
  $$ language plpgsql;
  /
  drop function "distinct";
  
  --关键字带单引号-合理报错
  drop function if exists 'distinct';
  create function 'distinct'(i integer)
  returns integer
  as $$
  begin
      return i+1;
  end;
  $$ language plpgsql;
  /
  --关键字带反引号-合理报错
  drop function if exists `distinct`;
  create function `distinct`(i integer)
  returns integer
  as $$
  begin
      return i+1;
  end;
  $$ language plpgsql;
  /