Ignore some field for results in kapacitor stream mode


I have some data ,data type like below, uid is field type

time    uid      source    event    click
1       usera    sourcea   eventa   1
2       userb    sourcea   eventb   1
3       usera    sourcea   eventb   1

Now I want to use kapacitor to read the data and do some handler and then store in other measurement
The handler is just get the uid field for new point like

time    uid      
1       usera    
2       userb   
3       usera

with kapacitor batch mode,I can do like that:

                SELECT "uid" FROM "db"."rp"."measurement" 

But how to realize it with kapcitor stream mode, that I can get new point just with uid and ignore source, event and click field. Is there some function like “select uid” in stream thant can get the special field I want?