Mehdi Ghapanvari speeds things up:
SQL Server columnstore indexes can improve the performance of aggregation queries. However, there are many cases where they are not efficient. I discussed one of these scenarios in “When Using a Clustered Columnstore Index Does Not Make Sense.” In that article, I discussed that columnstore indexes have three main features, one of which is Batch Mode Processing. SQL Server 2019 introduced a new feature called Batch Mode on Rowstore, which enables batch mode processing on Rowstore tables. In this article, I will explore this feature and explain why it is valuable in real-world scenarios.
In Mehdi’s solution, the question comes up of “Who would run an aggregation query on an OLTP system?” The answer is “everybody.” I’ve never seen an OTLP system with zero aggregation work. Perhaps these systems really do exist but some level of hybrid operation is the default that I’ve experienced.