Query Store use cases

Query Store is a very useful feature and can help you to identify and solve some performance problems, but also help you to learn about your workload and to be more familiar with it.

The main use cases are related to issues caused by a changed execution plan. Complex queries can have many potential execution plans and some of them can be performant, while some others lead to serious performance problems. The Query Optimizer does a great job when it generates execution plans but sometimes it comes up with a suboptimal plan. It is possible that two, totally different execution plans have similar costs. When a complex query has a good plan, the next plan for the same query can perform badly. The next plan might be generated when the old plan is not in the cache anymore. This happens when SQL Server is upgrading to a new version, when cumulative update or Service Pack is installed, when patching is performed, when a failover happens, and also when a new application or service...