What is plan regression in SQL Server?

Plan regression happens when SQL Server starts using the sub-optimal SQL plan to execute some T-SQL query. Usually you will see that some T-SQL query is executing really fast, but then it gets slower without any obvious reason. In this post you will see how can plan regression happen…. Read more

“You Shall Not Regress!!!” – How SQL Server 2017 prevents plan regressions?

SQL plan regression is a case when a T-SQL query that executed fine becomes much slower or uses more resources because the underlying SQL plan changed. SQL Server 2017 would not allow that kind of regressions if you enable new automatic tuning feature on your database…. Read more

Query Optimizer Additions in SQL Server 2016

In SQL Server 2016 we have introduced a number of new Query Optimizer improvements. This article summarizes some them and explains you can leverage the benefits of the new enhancements. Expect deep dive follow up articles for some of the enhancements. Here is the short list: Compatibility Level Guarantees Query Optimizer Improvements under Trace Flag… Read more