For a SQL Server database set at compatibility level 120 and above, the legacy cardinality estimator (CE version 70) can be activated at the database level by using the ALTER DATABASE SCOPED CONFIGURATION.SQL Copy ALTER DATABASE SCOPED CONFIGURATION SET LEGACY_CARDINALITY_ESTIMATION = ON; GO ...
For a SQL Server database set at compatibility level 120 and above, the legacy cardinality estimator (CE version 70) can be activated at the database level by using theALTER DATABASE SCOPED CONFIGURATION. SQL ALTERDATABASESCOPED CONFIGURATIONSETLEGACY_CARDINALITY_ESTIMATION =ON; GOSELECTname,valu...
For a SQL Server database set at compatibility level 120 and above, the legacy cardinality estimator (CE version 70) can be activated at the database level by using the ALTER DATABASE SCOPED CONFIGURATION.SQL Kopiera ALTER DATABASE SCOPED CONFIGURATION SET LEGACY_CARDINALITY_ESTIMATION = ON;...
参考资料 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/...
优化器有很多方式估算基数的算法,我们这里列举几种简单的方式,如果你想了解更多基数估计的算法。可以参考”SQL Server中关于基数估计如何计算预估行数的一些探讨“或官方文档Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator 如果谓词很简单,如“CustomerID=11142”,并且搜索值恰好是直方图RANGE...
Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator Summary: SQL Server 2014 introduces the first major redesign of the SQL Server Query Optimizer cardinality estimation process since version 7.0. The goal for the redesign was to improve accuracy, consistency and supportability of...
优化器有很多方式估算基数的算法,我们这里列举几种简单的方式,如果你想了解更多基数估计的算法。可以参考”SQL Server中关于基数估计如何计算预估行数的一些探讨“或官方文档Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator 如果谓词很简单,如“CustomerID=11142”,并且搜索值恰好是直方图RANGE...
SQL Server 2014 uses database compatibility level to determine if new cardinality estimator will be used. If the database compatibility level is 120, new cardinality estimator will be used. If you create a new database on SQL Server 2014, compatibility level will be 120. When you upgrade or...
Knowing that the CE has changed and purposefully was not overcautiously re-architected to avoid regressions, you need to prepare a little more carefully for a SQL Server 2014 upgrade if you will utilize the new Cardinality Estimator. Based on our experience so far, you need to kno...
You can read more about CE changes in the white paperOptimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator. For correlated columns in the 2014 CE, to derive cardinality we need to sort the filters according to their density, where the smallest density v...