Automatic Plan Correction

Jovan Popovic introduces a new tuning feature in SQL Server 2017:

How to identify plans that should be corrected?

SQL Server 2017 provides a new system view called sys.dm_db_tuning_recommendations that shows all identified plan regressions. You can select data from this view, find the difference between last known good plan and regressed plan, and the script that you can execute to manually fix regression.

Automatic plan correction

As a next step, you can let SQL Server 2017 to automatically correct any plan that regressed.

I like it when the database engine gets smarter, but I get the feeling I’d like there to be some finer-grained options around what gets considered a regression and when a sub-optimal plan gets swapped out.

Related Posts

Nested Loops, Hash, Or Merge: Which Is Best?

Grant Fritchey dodges the important questions: First response, also a joke, was the question at the title of this post: What is the preferred operator when joining tables: Hash Match, Nested Loops or Merge? While my immediate response to this question is, yes. Meaning, they’re all preferred, situationally. I decided to expand on that a […]

Read More

Parallelism Strategies For Grouping Operations

Itzik Ben-Gan continues his series on grouping data in SQL Server by looking at how these operations can go parallel: Besides needing to choose between various grouping and aggregation strategies (preordered Stream Aggregate, Sort + Stream Aggregate, Hash Aggregate), SQL Server also needs to choose whether to go with a serial or a parallel plan. […]

Read More

Categories