Automatic Tuning In SQL Server

Grant Fritchey is a fan of SQL Server 2017’s automatic tuning feature:

The core of automatic tuning at this point in time (because I’m sure it’s going to evolve) is the ability of the query engine to spot when a query has generated a new plan and that new plan is causing performance to degrade. This is known as a regression in the plan. It comes from bad parameter sniffing, changes in statistics, cumulative updates, or the big notorious one, the cardinality estimator introduced in SQL Server 2014 (it’s been almost four years, I’m not calling it new any more). Spotting a plan regression prior to SQL Server 2016 and the introduction of the Query Store was a major pain. However, now it’s easy. You can spot them by reading the data collected. Further, Microsoft can spot them by reading the data collected, and it does.

If the engine sees that a plan is causing a regression (you have to have Query Store enabled for this), then it will write out a suggestion for fixing it to the new DMV, sys.dm_db_tuning_recommendations. If you further enable automatic tuning on your database, then SQL Server can automatically substitute the last good plan for you, fixing the problem. Further, SQL Server monitors this fix and if, over time, it’s clear that the forced plan is causing problems, it will unforce the plan, again automagically.

Click through for more information, including a query to read from the tuning recommendations DMV.

Related Posts

Tuning Apache Spark Applications

Vidisha Gupta has a few tips for tuning Apache Spark programs: Data Serialization – Serialization plays an important role in increasing the performance of any application. Spark provides two serialization libraries – Java Serialization: By default, spark uses Java’s ObjectOutputStream framework which can work with any class that implements java.io.serializable. This serialization is flexible but slow and […]

Read More

A Compendium Of Bad (Or Misleading) Performance Tips

Grant Fritchey responds to a long list of performance tips of greater or (mostly) lesser value: Index the predicates in JOIN, WHERE, ORDER BY and GROUP BY clauses What about the HAVING clause? Does the column order matter? Should we put a single column or multi-column index? INCLUDE statements? What kind of index, clustered, non-clustered, […]

Read More

Categories

December 2017
MTWTFSS
« Nov Jan »
 123
45678910
11121314151617
18192021222324
25262728293031