set table with sum vs multiset with no sum - response (1) by Qaisar Aftab Kiani

My two cents...
Consider the index selections is same for both set and multiset cases. The multiset would be faster as there is no extra processing even checking the duplicate rows is not required. First of all Aggregation is a resource intensive process and during the insertions the duplicate rows check will require some extra time/processing and will take more ececution time.