DSQL Generation Example 参考资料 总结 PDW QO是paper描述了SQL Server MPP查询优化器的设计与实现,Paralled Data Warehouse产品的查询优化器(PDW QO)。PDW QO是基于SQL Server单机Cascade优化器技术实现的针对分布式查询的CBO优化器。PDW QO在控制节点采用两阶段方式制定DPlan(分布式执行计划): 基于单机Cascade优化器...
SQL Server PDW(Parallel DataWarehouse)是SQL Server的MPP版本,目前已经演进为Azure DataWarehouse部署在云上,用来存储大容量数据并处理分析型查询。总体上是一个share nothing的经典MPP架构,类似于Greenplum,它也会利用单机SQL Server作为其sharding data和meta data的存储+计算实例。 基本架构 集群中每个节点都部署单个S...
For example, Parameter Sensitive Plan (PSP) optimization was introduced in SQL Server 2022 (16.x) (compatibility level 160), which uses multiple active plans per query to address nonuniform data distributions. If your environment cannot use the latest compatibility level, Query Store hints using ...
The following example code selects all query_ids that have an optimization replay script in Query Store. Connect to the appropriate user database before running the example code.SQL Kopiraj SELECT q.query_id, t.query_sql_text, p.plan_id, TRY_CAST (p.query_plan AS XML) AS query_p...
Query optimization in Microsoft SQL Server PDW Srinath Shankar, Rimma Nehme, Josep Aguilar-Saborit, Andrew Chung, Mostafa Elhemali, Eric Robinson, Mahadevan Sankara Subramanian, David DeWitt, César Galindo-Legaria, Alan Halverson International Conference on Management of Data|May 2012 ...
The SQL Server Query Optimizer doesn't choose only the execution plan with the lowest resource cost; it chooses the plan that returns results to the user with a reasonable cost in resources and that returns the results the fastest. For example, processing a query in parallel typically uses ...
Applies to:SQL Server (Starting with SQL Server 2022 (16.x)) DisablesOptimized plan forcingfor a query. Optimized plan forcing reduces compilation overhead for repeating forced queries. Once the query execution plan is generated, s...
For example, if a table had 1 billion rows, under the old behavior it would have taken 200 million rows to be changed before auto-stats update kicks in. In SQL Server 2016, it would take only 1 million rows to trigger auto stats update. ...
Improved statistics loading framework: The optimizer internally improves the loading of statistics compared with SQL Server 2000. It now loads all and only the statistics it needs, improving optimization result quality and performance. Increased ability to automatically create statistics on computed columns...
Improved statistics loading framework: The optimizer internally improves the loading of statistics compared with SQL Server 2000. It now loads all and only the statistics it needs, improving optimization result quality and performance. Increased ability to automatically create statistics on computed columns...