streaming expressions substring-evaluator

[Aroop Ganguly]

Hey Team


Is there a way to extract a part of a string field and group by on it and 
obtain a histogram ?

for example the filed value is DateTime of the form: 20180911T00 and 
I want to do a substring like substring(field1,0,7), and then do a streaming 
expression of the form :

rollup(
    select(
     search(col1,fl=“field1”,sort=“field1 asc”), substring(field1,0,7) as date)
   ,on= date, count(*)
)

Is there a substring operator available or an alternate in streaming 
expressions?

Thanks
Aroop