http://www.scarydba.com/2011/06/15/rebind-and-rewind-in-execution-plans/ Ever looked at an execution plan? If you answered no, you can't possibly have ever tried to tune a query, or, you're doing it wrong. For every one else, no doubt you've looked a…

转载请注明出处 由于工作及学习需要,最近看了一下<Dissecting SQL Server Execution Plans>,这是少有的专门描述执行计划的优秀书籍,为了快速查找并供入门同行学习,粗略翻译了本书,并进行连载,由于专业及英语水平严重不足,所以建议有兴趣有能力的读者看原书,同时期待各位指出翻译不足.下载地址:点击打开链接 本文是一个总入口,方便阅读,共8章,由于篇幅较多,每章的每节独立成一篇博文,每翻译完一节就发布一节,敬请留意 第一章: 第一节:当查询提交时会发生什么事情 第二节…

<Pro SQL Server Internals> 作者: Dmitri Korotkevitch 出版社: Apress出版年: 2016-12-29页数: 804定价: USD 59.99装帧: PaperbackISBN: 9781484219638 统计 SQL Server查询优化器在为查询选择执行计划时使用基于成本的模型.它估计不同执行计划的成本,并选择成本最低的一个.但是,请记住,SQL Server并不搜索查询可用的最佳执行计划,因为评估所有可能的替代方案在CPU方面都是耗时…

From http://blog.csdn.net/wujiandao/article/details/6621073 1. Four ways to get execution plan(anytime you want, for specified sql) • Execute the SQL statement EXPLAIN PLAN, and then query the table where the output was written. • Query a dynamic per…

后面的练习中需要下载 Demo 数据库, 有很多不同的版本, 可以根据个人需要下载.  下载地址 -http://msftdbprodsamples.codeplex.com/ 1. 什么是执行计划 查询优化器对输入的 T-SQL 查询语句通过"计算"而选择出效率最高的一种执行方案,这个执行方案就是执行计划. 执行计划可以告诉你这个查询将会被如何执行或者已经被如何执行过,可以通过执行计划看到 SQL 代码中那些效率比较低的地方. 查看执行计划的方式我们可以通过图形化的界面,或者文本,或…

引用自:http://rusanu.com/2013/08/01/understanding-how-sql-server-executes-a-query/ Understanding how SQL Server executes a query August 1st, 2013 If you are a developer writing applications that use SQL Server and you are wondering what exactly happens…

https://www.codeproject.com/Articles/630346/Understanding-how-SQL-Server-executes-a-query https://www.codeproject.com/Articles/732812/How-to-analyse-SQL-Server-performance     This article will help you write better database code and will help you ge…

http://sqlserverbuilds.blogspot.jp/   What version of SQL Server do I have? This unofficial build chart lists all of the known Service Packs (SP), Cumulative Updates (CU), patches, hotfixes and other builds of MS SQL Server 2016, 2014, 2012, 2008 R2,…

原帖地址 What version of SQL Server do I have? This unofficial build chart lists all of the known Service Packs (SP), Cumulative Updates (CU), patches, hotfixes and other builds of MS SQL Server 2014, 2012, 2008 R2, 2008, 2005, 2000, 7.0, 6.5 and 6.0 tha…

RTM (no SP) SP1 SP2 SP3 SP4 SQL Server 2014      codename Hekaton  12.00.2000.8 SQL Server 2012      codename Denali 11.00.2100.60 11.00.3000.0 11.00.5058.0 SQL Server 2008 R2      codename Kilimanjaro 10.50.1600.1 10.50.2500.0 or 10.51.2500.0 10.50.…

在SQL Server中执行查询时,有一些操作会产生中间结果集,例如:排序操作,Hash Join和Hash Aggregate操作产生的Hash Table,游标等,SQL Server查询优化器使用 Worktable 和 Workfile 存储中间结果集,对中间结果集执行后续操作,以响应用户的请求. 一,Spool 操作符 Spool的中文解释是假脱机,是指两个设备处于联机状态,只不过都在后台运行. 假脱机的原理,通俗的说,是在两个设备之间进行数据交换,一个设备传输数据的速度快,一个设备传…

QUESTION 13 View the Exhibit.Examine the following command that is executed for the TRANSPORT table in the SH schema:SQL> SELECT DBMS_STATS.CREATE_EXTENDED_STATS('sh', 'customers_obe', '(country_id,cust_state_province)') FROM dual;Which statement des…

查看Execution Plan时,在Sort Operator上,发现一个Warning:Operator used tempdb to spill data during execution with spill level 1 以XML格式查看执行计划,发现一个SpillToTempDb的节点: <Warnings> <SpillToTempDb SpillLevel="1" /> </Warnings> Sort Warnings are r…

Table 有两种结构:BTree 和 Heap,一个table的结构必定是其中之一.如果在表上创建clustered index,那么表的结构是BTree:如果表上没有创建Clustered index,那么表的结构是Heap.Heap 可以看作一种特殊的Index结构,Index ID 是0,只有一层,Leaf Level,或Data level.BTree 的Clustered Index的ID 是1, Leaf Level是Table的Data Page. Index pages fal…

对Oracle数据库整体性能的优化,首先要关注的是在有性能问题时数据库排名前几位等待事件是哪些.Oracle等待事件众多,随着版本的升级,数量还在不断增加,可以通过v$event_name查到当前数据库版本包含的等待事件.例如我在Linux平台查11.2.0.4版本的Oracle是有1367个等待事件.SELECT name FROM V$EVENT_NAME ORDER BY name; 如此多的等待事件自然是要分类汇总,并对常见的等待事件有比较深入的认识,才能在Oracle数据库调优这条路上…

http://www.idevelopment.info/data/Oracle/DBA_tips/Database_Administration/DBA_26.shtml DBA Tips Archive for Oracle        Oracle Created (Default) Database Users by Jeff Hunter, Sr. Database Administrator Overview During database creation, Oracle cre…

Mysql 5.7.17发布了,主要修复: Changes in MySQL 5.7.17 (2016-12-12, General Availability) Compilation Notes MySQL Enterprise Notes Packaging Notes Security Notes Test Suite Notes Functionality Added or Changed Bugs Fixed Compilation Notes For GCC versions hig…

  1:查看.修改AWR报告快照数据的采样间隔.保存策略 SQL> COL DBID FOR 999999999999 SQL> COL SNAP_INTERVAL FOR A26 SQL> COL RETENTION FOR A26 SQL> COL TOPNSQL FOR A10 SQL> select * from dba_hist_wr_control;            DBID SNAP_INTERVAL              RETENTION     …

ORACLE的执行计划分为预估执行计划和实际执行计划.其中,你用Toad.PL/SQL Developer.SQL Developer.EXPLAIN PLAN FOR或者SET ATUOTRACE TRACEONLY等获取的执行计划都是预估的执行计划.有时候预估执行计划和实际执行计划有很大的差别,所以有时候,调优的时候需要对比实际执行计划和预估的执行计划,不能被预估的执行计划给欺骗了.那么我们怎么查看实际的执行计划呢?   方法1:查询v$sql_plan视图中的实际执行计划 1:在窗口执行下…

转自:http://zjxbw.blog.51cto.com/2808787/543792 Ctrl+Shift+L    显示所有快捷键 Ctrl+K      参照选中的词(Word)快速定位到下一个 Ctrl+Shift+K    参照选中的词(Word)快速定位到上一个  Ctrl+O      快速显示OutLine  Ctrl+T      快速显示当前类的继承结构 Ctrl+Shift+X    把选中文本全部改为大写 Ctrl+Shift+Y    把选中文本全部改为小写 Ctr…

BIND and REBIND options for packages and plans There are several options you can use for binding or rebinding plans and packages. Some of the options are common for both bind and rebind and for both plans and packages. Defaults: The default for an op…

16.1 Introduction to SQL Tuning Identifying high load or top SQL statements that are responsible for a large share of the application workload and system resources, by reviewing past SQL execution history available in the system Verifying that the ex…

分享一下SQLSERVER技术交流QQ群里的群共享资源 SQLSERVER技术交流QQ群已经开了一段时间了,人数已经有了100多号人, 而群里面很多SQLSERVER爱好者上传了他们宝贵的SQLSERVER学习资料给QQ群里面的每个成员, 不过我个人觉得这些宝贵的学习资源应该让更多人享受得到,不应该只留在QQ群里的群成员, 所以我特意把这些资源全部下载下来,然后放到金山快盘,共享这些资源让大家去下载,有好东西当然是大家一起分享啦o(∩_∩)o !! 里面有一些非常好的SQLSERVER pdf格…

http://www.onjava.com/pub/a/onjava/2001/05/30/optimization.htmlComparing the performance of LinkedLists and ArrayLists (and Vectors) (Page last updated May 2001, Added 2001-06-18, Author Jack Shirazi, Publisher OnJava). Tips: ArrayList is faster than…

In a Nested Loops Join, for example, the first accessed table is called the outer table and the second one the inner table. In a Hash Join, the first accessed table is the build input and the second one the probe input. Stream Aggregate and Merge Joi…

http://flink.apache.org/news/2015/03/13/peeking-into-Apache-Flinks-Engine-Room.html   Join Processing in Apache Flink In this blog post, we cut through Apache Flink's layered architecture and take a look at its internals with a focus on how it handle…

 https://ci.apache.org/projects/flink/flink-docs-release-0.10/apis/programming_guide.html   Example Program 编程的风格和spark很类似, ExecutionEnvironment  -- SparkContext DataSet – RDD Transformations 这里用Java的接口,所以传入function需要用FlatMapFunction类对象   public clas…

The auto_explain module provides a means for logging execution plans of slow statements automatically, without having to run EXPLAIN by hand. This is especially helpful for tracking down un-optimized queries in large applications. https://www.postgre…

Tuning Methodology When dealing with performance problems, database professionals tend to focus on the technical aspects of the system, such as resource queues, resource utilization, and so on. However, users perceive performance problems simply as w…

安装 ORACLE 时,若没有为下列用户重设密码,则其默认密码如下: 用户名 / 密码 登录身份 说明 sys/change_on_install SYSDBA 或 SYSOPER 不能以 NORMAL 登录,可作为默认的系统管理员 system/manager SYSDBA 或 NORMAL 不能以 SYSOPER 登录,可作为默认的系统管理员 sysman/oem_temp sysman 为 oms 的用户名 scott/tiger NORMAL 普通用户 aqadm /aqadm SYSD…