Hi, I am lost when reading the content.... what is *" "* *precise etc.....?
> In DDL, we want to replace the prefix path match with the *precise path > match* What is *precise path match*? > For example the old versions query "count timeseries root.sg " will be > implemented as "count timeseries root.sg.** ". OK, it is clear. > Besides, the old query > "count timeseries root.sg.*.s " will count timeseries like "root.sg.d.s.t " > because its prefix path matches "root.sg.*.s " but the new query won't do > that any more because its full path doesn't match "root.sg.*.s ". So if we want to count timesereis "root.sg.d.s.t " (I mean, root.sg.d.s.t is a timeseries, not a prefix path), we need to use "count timeseries root.sg.*.s.*"? in your DML paragraph, I can not understand what *"select * "* is. Best, ----------------------------------- Xiangdong Huang School of Software, Tsinghua University 黄向东 清华大学 软件学院 周钰坤 <[email protected]> 于2021年8月26日周四 下午12:47写道： > > Hi > > We want to introduce a new *wildcard ***, to improve the DDL and DML of > IoTDB-SQL. > Wildcard ** will represent one or more levels in the path and the existing > wildcard * will only represent one level in the path even if it's at the > tail of the path. > > In DDL, we want to replace the prefix path match with the *precise path > match*, which means the given path will be the pattern of result elements' > full path. The prefix path match could be implemented by leveraging > wildcard **. This change can help users do operations more precisely. > For example the old versions query "count timeseries root.sg " will be > implemented as "count timeseries root.sg.** ". Besides, the old query > "count timeseries root.sg.*.s " will count timeseries like "root.sg.d.s.t " > because its prefix path matches "root.sg.*.s " but the new query won't do > that any more because its full path doesn't match "root.sg.*.s ". > The same changes will be applyed on DDL of storage group, entity and normal > nodes. > > In DML, after introduce wildcard **, *"select * "* won't query all > timeseries in the subtree represented by the given path, but *"select ** "* > will do that. *"select * "* will only query the timeseries on the next > level of the given path. > For example, the new query "select * from root.sg.d" will only query > timeseries like "root.sg.d.s" but not query timeseries like > "root.sg.d.a.s", while "select ** from root.sg.d" will query them all. > Of course, we want to implement *precise path match* in DML too. > > Best > ----------------------------- > Yukun zhou > School of software, Tsinghua University > > 周钰坤 > 清华大学 软件学院
