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 ...
MS SQL Server is used as an experimental approach to examine the proposed techniques.Haxhijaha, BlertaAjdari, JauminRaufi, BujarZenuni, XhemalIsmaili, FlorieInternational Journal on Information Technologies & Security
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...
9.对这个最优plan应用post-optimization rules,论文没有给出这个rules是什么,个人理解可能是topN之类的规则。 10.以bottom-up方式生成DSQL 11.对DSQL应用post-DSQL-generation rules 12.返回最终DSQL执行计划 Cost Model PDW优化器的代价评估模型中计算了data movement算子的代价。 Cost Model假设 从0开始建立代价评...
Control node 是集群的入口点,前端应用于control node连接并发送请求,其上有一个PDW engine,做全局性的管理控制:distributed query优化、执行调度管理,DMS管理,权限检查,对外接口。内部的SQL server上有一个shell database,保存全局信息:global metadata/global statistics/数据分布/权限信息,和GP一样没有user data。
SQL Server 2014 introduced a new Cardinality Estimator to address short-comings in the cardinality estimator that was used in previous versions of the product. In the latest release, we have identified and fixed some inefficiencies with the new models that could result in bad plans. ...
· 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. · Minimum sample size: A minimum of 8 megabytes (MB) of da...
Clearer and more consistent display of histograms: DBCC SHOW_STATISTICS is improved because histograms are always scaled before being stored in the catalogs. Inferred date correlation constraints: By enabling the DATE_CORRELATION_OPTIMIZATION database setting, you can cause SQL Server to maintain informat...
The execution plan describes the sequence of operations, physical and logical, that SQL ServerTM will perform in order to fulfill the query and produce the desired resultset. The execution plan is produced by a database engine component called Query Optimizer during the optimization phase of query...
from parsing the initial query to how the Query Optimizer tries to find the best possible execution plan for every query submitted to SQL Server. We’ve also looked at the complexity of the optimization process, including the challenges it faces in exploring the potentially vast search space and...