Hi, +1. ----------------------------------- Xiangdong Huang School of Software, Tsinghua University
黄向东 清华大学 软件学院 孙泽嵩 <[email protected]> 于2021年3月8日周一 下午5:48写道： > Hi Zihan, > > I support the first solution, though “select ** from root” may be strange > : ) > > Besides, I’d like to append another case: > > I looked up the usage of wildstar in Linux : > > /tmp/* matches any file in /tmp. // Substitutes for any number of > characters, except /. > /tmp/** matches all files and directories underneath /tmp. // Substitutes > for any number of characters, including /. > > So we should also consider that ** also contains zero layer. > For example, if we have some storage groups: > > root.a.sg1 > root.a.b.sg2 > root.b.sg3 > > For "delete storage group root.a", we do not delete any sg. > For "delete storage group root.a.*" we delete root.a.sg1 > For "delete storage group root.a.sg1.*" we do not delete any sg. > For "delete storage group root.a.**" we delete root.a.sg1, root.a.b.sg2 > > If we also have another storage group “root.a”: > > For "delete storage group root.a", we delete root.a > For "delete storage group root.a.*" we delete root.a.sg1 (because * does > not include zero layer) > For "delete storage group root.a.**" we delete root.a, root.a.sg1, > root.a.b.sg2 (because ** includes zero layer) > > > Best, > ----------------------------------- > Zesong Sun > School of Software, Tsinghua University > > 孙泽嵩 > 清华大学 软件学院 > > > 2021年3月4日 11:13，weizihan0110 <[email protected]> 写道： > > > > Hi all: > > The initial discussion is at > https://issues.apache.org/jira/browse/IOTDB-1160) > > > > First Solution: > > > > "*" matches just one layer and "**" matches one or more layers. As a > result, the SQL statement "select * from root" have to be converted into > "select ** from root". It seems a little bit disappointing. > > > > Second Solution: > > "*" matches one or more layers by default. And we can put something like > "1 layer"(layer is the keyword) in the SQL statement to strengthen the > semantics to match just one layer. More, "2 layers" to match just two > layers and so on. This solution can be more scalable, I think. > > > > > > Does anyone have any idea about this? Welcome to discuss. > >
