Aggregation issue for multiple aggregation value selection

I have created three varibales
agg1=id.keyword,name.keyword,surname.keyword
agg2=id.keyword,name.keyword,surname.keyword
agg3=id.keyword,name.keyword,surname.keyword

i have elastic source database
i select one vaariable , or max 3 varibales based on i want to aggregate

I have written following query but if disint select agg2 then i am getting blanck result it should give me result for agg1 but it diidnt
what chnages i have to do also i am using volkolabs