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...
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/...
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,value...
在SQL Server中,我们要看懂执行计划和统计信息,我们可能需要深刻理解一些关键词,例如密度(Density)、选择性(Selectivity)、谓词(predicate)、基数(Cardinality)。前阵子,对密度和选择性的概念模糊了,刚好看了Query Tuning Fundamentals: Density, Predicates, Selectivity, and Cardinality这篇文章, 遂结合自己的理解、以及...
Applies to:SQL Server (Starting with SQL Server 2019 (15.x)), Azure SQL Database Table variable deferred compilationimproves plan quality and overall performance for queries referencing table variables. During optimization and initial plan compilation, this feature propagates cardinality estimates tha...
EXEC sys.sp_query_store_set_hints @query_id = 39, @query_hints = N'OPTION (USEHINT (''FORCE_LEGACY_CARDINALITY_ESTIMATION''))'; 以下示例应用提示,以强制实施最大内存授予大小(在配置的内存限制query_id为PERCENT39,在查询存储中标识):
For more information, see Join containment assumption in the New Cardinality Estimator degrades query performance.Starting with SQL Server 2016 (13.x) Service Pack 1, to accomplish this at the query level, add the USE HINT 'ASSUME_JOIN_PREDICATE_DEPENDS_ON_FILTERS' query hint instead of using...
The following example applies the hint to force the legacy cardinality estimator to query_id 39, identified in Query Store: SQL Copy EXEC sys.sp_query_store_set_hints @query_id = 39, @query_hints = N'OPTION (USE HINT (...
New cardinality estimator - good and bad In-Memory tables - no locks, hash index AlwaysOn Availability Groups for availability and reporting servers Go fast with SQL Server 2012 performance Window Function Enhancements - faster aggregate computations ...
Optimizing Your Query Plans with the SQL Server 2014 Cardinality Estimator(使用 SQL Server 2014 基數估算程式最佳化您的查詢計劃) PARAMETER_SNIFFING 資源 參數探測 參數的運用\(英文\) QUERY_OPTIMIZER_HOTFIXES 資源 追蹤旗標 SQL Server 查詢最佳化工具 Hotfix 追蹤旗標 4199 服務模型 ...