最近一年一直在做PolarDB的并行优化器,过程中调研了各种分布式数据库系统的优化和执行框架,后续几篇文章将一一分享,首先介绍对PolarDB MySQL的并行优化框架影响最大的,也就是SQL Server PDW。 SQL Server PDW…
SQL Server PDW是一个share nothing的MPP架构,部署方式为一个control node(控制节点)和多个compute node(计算节点),架构图如下: control node 一个SQL Server RDBMS实例 提供对客户端应用的连接接口 负责query的语法解析 创建分布式执行计划 向compute节点下发执行计划的steps trace执行计划的steps 汇集最终结果,并返回...
应该避免在 SQL 查询中使用 IN子句,而是用exists来代替。 例如,在下面的查询中,我们首先从ItemInfo表中找到产品 ItemInternalKey,然后在 itemcode表中查找相应的记录。 select top 1000 * from ItemCode where ItemInternalKey in (select top 100 ItemInternalKey from ItemInfo) 下面是用Exists来实现的相同功能 ...
Why, when and how to rebuild and reorganize SQL Server indexes How to format SQL code in SQL Server Management Studio SQL Server Management Studio (SSMS) – how to save results with headers How to create and optimize SQL Server indexes for better performance Reverting your SQL Server database...
Query optimization 發行項 2012/11/21 If you would like to Optimize your SQL Server Query, Tune slow queries in SQL Server and make them run faster follow the steps in below blogA query in considered to be slow when it is executing for longer duration than expected. Total duration of ...
This paper examines several techniques for improving database query performance, by looking at some common operations and examining ways to enhance their execution. MS SQL Server is used as an experimental approach to examine the proposed techniques.Blerta Haxhijaha...
Query optimization for such system is a challenging and important problem. In this paper we describe the Query Optimizer inside the SQL Server Parallel Data Warehouse product (PDW QO). We leverage existing QO technology in Microsoft SQL Server to implement a cost-based optimizer for distributed ...
What are best practices for query optimization in SQL Server? Well-designed queries are critical for SQL Server database performance. Inefficient queries can create overly-complex algorithms that use excessive resources and slow performance overall. Optimizing queries can have an outsized impact on pr...
·Inferred date correlation constraints:By enabling the DATE_CORRELATION_OPTIMIZATION database setting, you can cause SQL Server to maintain information about the correlation betweendatetimefields across a pair of tables linked by a foreign key. This information is used to allow implied predicates to ...
Optimization is the process the DBMS uses to choose the most efficient execution plan for the query you have written. Since SQL is a declarative language, you tell SQLwhat to do, butnot how to do it. This means, many of the mechanics and in’s and out’s are lets to the DBMS. It...