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 d
SQL Server优化器原来的搜索空间就很大,引入data movement(DMS)算子后,进一步增大了。除非query非常简单,否则原有的枚举算法已经不太适用了。本节,论文描述了一种bottom-up的搜索策略。目前,PDW QO使用了bottom-up的搜索策略,top-down的剪枝技术。伪代码如下: PWDOptimizer方法对应于图2步骤4的QueryOptimizer: 将SQL...
(c)在单机SQL Server中完成单机优化,形成Final (Serial) Memo,传递给PDW optimizer,枚举Shuffle/Replicate等算子,生成Augmented (Parallel) Memo。 (d)从c的Parallel Memo中选出最优分布式计划 (e)转换为DSQL的plan描述,其中包括DMS operation + SQL operation... 总结 SQL Server PDW的并行优化方案还是非常优雅的...
In SQL Server 2016 we have introduced a number of new Query Optimizer improvements. This article summarizes some them and explains you can leverage the benefits of the new enhancements. Expect deep dive follow up articles for some of the enhancements. Here is the short list: Compatibility...
Statistical Data in SQL Server 2008 Microsoft SQL Server 2008 collects statistics about individual columns (single-column statistics) or sets of columns (multicolumn statistics). Statistics are used by the query optimizer to estimate the selectivity of expressions, and thus the size of intermediate an...
What's New for Statistics in SQL Server 2005? SQL Server 2005 has a number of new statistics features that allow the query optimizer to choose better query plans for a broader range of queries, or otherwise improve the management of statistics. These include the following enhancements: ...
Applies ToSQL Server 2017 Developer SQL Server 2017 Enterprise SQL Server 2017 Enterprise Core 改進 假設您已安裝 SQL Server 2017。 這個改良會引入一個新的使用提示「QUERY_OPTIMIZER_COMPATIBILITY_LEVEL_n ' ,在查詢層級強制執行查詢優化...
假設您已安裝 SQL Server 2017。 這個改良會引入一個新的使用提示「QUERY_OPTIMIZER_COMPATIBILITY_LEVEL_n ' ,在查詢層級強制執行查詢優化程式列為,就像是使用資料庫相容性等級n編譯的查詢,其中 n 是 來自下列清單的支援資料庫相容性等級:100、110、120、130或140。
The SQL Server Query Optimizer To understand how to write SQL code for SQL Server that performs well, it is important to appreciate how the query opti
query plan asTimeOutunderReason For Early Termination of Statement Optimization. It's important to understand that this threshold isn't based on clock time but on the number of possibilities considered by the optimizer. In current SQL Server QO versions, over a half million ta...