14. SQL Performance Tuning recommends to use minimal number of sub queries, if possible. Example: --Do not use: SELECT id, manufacturer, model FROM cars WHERE price = ( SELECT MAX(price) FROM cars_bmw ) AND year = ( SELECT MAX(year) FROM cars_bmw ) --Use: SELECT id, manufacturer,...
Hardware performance is constantly improving, which can lead to an attitude suggesting that other methods of performance tuning are no longer important. Upgrades to SQL Server—especially to the optimizer, which helps determine how a query is executed, and the query engine, which executes the query...
以下是版工整理出的一些数据库规划、SQL performance tuning 简单心得,让长年钻研 .NET、AJAX、一堆高深 ooxx framework,却无暇研究 SQL statement 的程序员,透过最短时间对本帖的阅读,能避免踩到一些 SQL 的性能地雷。 (注:本帖的 SQL 语句皆经过测试可正常执行无误。有兴趣实验者,可直接拷贝后,粘贴至 SQL S...
以下是版工整理出的一些数据库规划、SQL performance tuning 简单心得,让长年钻研 .NET、AJAX、一堆高深 ooxx framework,却无暇研究 SQL statement 的程序员,透过最短时间对本帖的阅读,能避免踩到一些 SQL 的性能地雷。 (注:本帖的 SQL 语句皆经过测试可正常执行无误。有兴趣实验者,可直接拷贝后,粘贴至 SQL S...
Spark SQL 之 Performance Tuning & Distributed SQL Engine 转载请注明出处:http://www.cnblogs.com/BYRans/ 缓存数据至内存(Caching Data In Memory) Spark SQL可以通过调用sqlContext.cacheTable("tableName") 或者dataFrame.cache(),将表用一种柱状格式( an inmemory columnar format)缓存至内存中。然后Spa...
5. Top N queries by bottleneck resource. Using profiler output or DMV to find out top n queries, then tune the single execution cost or reduce the execution number. 6. Wait stats. SQL Query Duration = CPU Time/# of CPU in used + Wait Time. Both duration and CPU time could be found...
You can improve your SQL Server 2005 Compact Edition (SQL Server Compact Edition) application performance by optimizing the queries you use. The following sections outline techniques you can use to optimize query performance.Improve IndexesCreating useful indexes is one of the most important ways to ...
Let me clarify that my intent was to bring out how SQL Server processes a BACKWARD scan of an Index. The queries choosing different plans can be because of multiple reasons. Anyway, we can achieve the same with the below queries which have similar predicates , but then I had to f...
-f pro.sql pro.sql 为业务逻辑脚本 Spark performance tuning-advanced For readers who are willing to understand the underlying principles of Spark, this article sorts out the interaction diagrams of three common task submission methods, such as standalone, Yarn-client, and Yarn-cluster, to help ...
Functions that are called from PL/SQL queries, where the functions might be executed millions of times. You will want to look at all performance features to make the function as efficient as possible, and perhaps a function-based index to precompute the results for each row and save on quer...