The groupBy operation doesn't involve any repartitioning. The groupBy operation converts the input stream into a grouped stream. The main function of the groupBy operation is to modify the behavior of the subsequent aggregate function. The following diagram shows how the groupBy operation groups the tuples of a single partition:
Working of the groupBy operation
- If the
groupByoperation is used before the partition aggregate, then the partition aggregate will run the aggregate on each group created within the partition. - If the
groupByoperation is used before the aggregate, then in that case, tuples of the same batch are first repartitioned into a single partition and then thegroupByoperation is applied on each single partition. At the end, it will perform the aggregate operation on each group.
So far, we have covered the basics of the Trident APIs. In the following section, we will cover how to write a non-transactional topology in Trident.
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