How many distribution buckets get created when we use Round Robin distribution scheme on U-SQL table?

Question

If we don't specify number of distributions per partition then how many distributions get created with Round Robin distribution scheme? Does Clustered Index key has some impact on number of distributions e.g. Can it cause different number of distribution buckets per partition?

Answer 1

If you don't specify the number of distributions by using INTO clause, then the number will be chosen based on the size of data in your first insert.

The mechanics are described here: U-SQL Table Partitions and Distributions