Another option for tracking the cardinality estimation process is to use the extended event namedquery_optimizer_estimate_cardinality. The following Transact-SQL code sample runs on SQL Server. It writes a .xel file toC:\Temp\(although you can change the path). When you open the .xel file...
Another option for tracking the cardinality estimation process is to use the extended event namedquery_optimizer_estimate_cardinality. The following Transact-SQL code sample runs on SQL Server. It writes a .xel file toC:\Temp\(although you can change the path). When you open the .xel file ...
https://docs.microsoft.com/en-us/sql/relational-databases/performance/cardinality-estimation-sql-server?view=sql-server-2017 https://blogs.msdn.microsoft.com/psssql/2015/06/16/identifying-sql-server-2014-new-cardinality-estimator-issues-and-service-pack-1-improvement/...
这个动作称之为基数计算(cardinality estimation)。数据库分析引擎会基于这些信息判断选择逻辑或物理的操作符,操作成本等等,生成一系列执行计划并最终挑选一个合适的执行计划。 在SQL Server 2014中,基数计算与之前的版本相比出现了较大的变化,并且这些变化对执行计划的生成有客观的促进作用。新的基数计算相对于之前的版本...
SQL Server creates and maintains statistics for temporary tables, which lead to better cardinality estimation and optimal execution plan generation. Table variables have no statistics, which can result in poor cardinality estimation and non-optimal execution plan creation. When you add ...
One of the performance improvement in SQL Server 2014 is the redesign of cardinality estimation. The component which does cardinality estimation (CE) is called cardinality estimator. It is the essential component of SQL query processor for query plan generation. Cardinality estimates are predictions ...
CREATE EVENT SESSION [XeNewCE] ON SERVER ADD EVENT sqlserver.query_optimizer_estimate_cardinality( ACTION(sqlserver.sql_text)), ADD EVENT sqlserver.query_optimizer_force_both_cardinality_estimation_behaviors ADD TARGET package0.event_file(SET filename=N'H:\Demo\XeNewCE.xel',m...
Status Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. References Cardinality Estimation (SQL Server) Learn about theterminologyMicrosoft uses to describe software updates.
the column is considered stationary instead of ascending. Therefore, the ascending key is not detected, and trace flags 2389 and 2390 that are usually used to fix the ascending keys problem do not work. This causes poor cardinality e...
The role CE is playing in the process to generate a good query plan is important. One hardly can expect a great Query Execution Plan as a result when the CE would estimates would be completely off workload which required SQL Server code fixes circled around issues ...