编译了一个新的函数,负责请求优化器的Memo数据,类似于SQL Server中的"showplan XML"函数。当发出PDW编译请求后,SQL Server会以XML格式返回MEMO数据 扩展SQL语法,以支持PDW。PDW的目标是与SQL Server完全兼容,因此,这个扩展仅限于针对特定的分布式执行策略的增加少量query hit。 扩展优化器搜索空间,根据数据分布信息,生...
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…
IN 和 EXISTS 子句的使用 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...
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 query execution. By properly abstracting metadata we can readily reuse existing logic for query simplification, space exploration and ...
SQL Server 2022 扩展了智能查询处理 (IQP) 功能系列,最受期待的功能之一是参数敏感计划优化(parameter-sensitive-plan-optimization)。 我开始测试这个新功能。在这篇文章中,您将找到一些信息来了解它的工作原理并进行首次测试。 参数敏感计划的问题 参数敏感计划,也称为“参数嗅探”,是一种由数据分布不均匀引起的场...
When it is not possible to avoid operation on the field, use an index built on that expression. This can be done in two ways: Create a calculated field based on your expression. Create a view, and build an index on it. NoteSQL Server requires certain conditions to be met in order to...
Use advance techniques in canvas apps to perform custom updates and optimization 认证 Microsoft Certified: Azure Database Administrator Associate - Certifications 使用Microsoft PaaS 关系数据库产品/服务,管理云、本地和混合关系数据库的 SQL Server 数据库基础结构。
When it is not possible to avoid operation on the field, use an index built on that expression. This can be done in two ways: Create a calculated field based on your expression. Create a view, and build an index on it. NoteSQL Server requires certain conditions to be met in order to...
For SQL Server to SQL Server migrations, if this issue existed in the source SQL Server, migrating to a newer version of SQL Server as-is will not address this scenario.SQL Server compiles query plans on stored procedures by using sniffing the input parameters at the first compile, gen...
Since each SQL batch has the potential of creating multiple plans, and each query variant plan has an independent entry in the plan cache, it is possible to reach the default maximum number of allowed plan entries. If the plan cache eviction rate is o...