本章提要-------------------------------------术语, 选择性与基数, 软解析与硬解析, 绑定变量, 扩展的游标共享SQL语句生命周期, 特别关注解析部分------------------------------------- 选择性和基数    选择性: 操作比例, 比如一个表中有120条记录, 通过条件过滤后, 剩下18条, 选择性就是0.15(18/120)    基数  : 就是一个表中一共的记录, 例如上例中 120游标的生命周期    打开游标,…

最近在给自己的服务器框架加上统计信息,其中一项就是统计创建的对象数,以及当前还存在的对象数,那么自然以对象名字作key.但写着写着,忽然纠结是用std::string还是const char *作key,哪个效率高些.由于这服务器框架业务逻辑全在lua脚本,在C++需要统计的对象没几个,其实用哪个没多大区别.我纠结的是,很久之前就知道这两者效率区别不大,但直到现在我都还没搞清楚为啥,于是写些代码来测试. V1版本的代码如下: #ifndef __MAP_H__ #define __MAP_H__…

insert操作卡死的处理过程 先看看insert为什么被卡死 SQL> select sql_id from v$sql where sql_text like 'delete from std_contract%'; SQL_ID ------------- 9wx6s3p84v3xw SQL> set long 9999 SQL> select sql_text from v$sql where sql_id ='9wx6s3p84v3xw'; SQL_TEXT ---------…

一.问题起源 淘宝搜索的博客 http://www.searchtb.com/2011/01/zookeeper-research.html  提到Paxos是zookeeper的灵魂 有一篇文章标题更是以“Zookeeper全解析——Paxos作为灵魂” 作为标题,认为是zookeeper的基础: “ Google的Chubby,Apache的Zookeeper都是基于它的理论来实现的,Paxos还被认为是到目前为止唯一的分布式一致性算法,其它的算法都是Paxos的改进或简化.有个问题要提一下…

Home GameWorks Blog Life of a triangle - NVIDIA's logical pipeline   Life of a triangle - NVIDIA's logical pipeline Facebook Twitter LinkedIn Google+ By Christoph Kubisch, posted Mar 16 2015 at 12:52PM Tags:  GameWorks GameWorks Expert Developer DX12…

DOM(增删改查): 查询 1.获取元素 1.1标准DOM API document.getElementById document.getElementsByTagName document.getElementsByName document.getElementsByClassName document.querySelectorAll 1.2亲属访问 1.3属性获取 getAttribute getAttributeNode 2.获取属性值 var attrNode=node.getAt…

Using Events The Components and Classes of Ext JS fire a broad range of events at various points in their lifecycle. Events allow your code to react to changes around your application. They are a key concept within Ext JS. 在ExtJS组件和类的生命周期中,会触发许多类型的事件…

http://www.tocker.ca/categories/myisam Converting MyISAM to InnoDB and a lesson on variance I'm about to start working through converting a large MySQL installation to InnoDB. For the particular use case durability is desired, and with MyISAM a loss…

In the Part 1 we talked about tasks and different stages of the build lifecycle. But after I published it I realized that before we jump into Gradle specifics it is very important to understand what we are dealing with - understand its syntax and sto…

# sample data d <- data.frame(expand.grid(x=letters[1:4], g=factor(1:2)), y=rnorm(8)) # Figure 1a, 1b, and 1c. ggplot(d, aes(x=x, y=y, colour=g)) + opts(title="Figure 1a") + geom_line() + geom_point() ggplot(d, aes(x=x, y=y, colour=g, group=g…