In C++, namespaces can be nested, and resolution of namespace variables is hierarchical. For example, in the following code, namespace inner is created inside namespace outer, which is inside the global namespace. In the line "int z = x", x refe…

Before introducing classes, I first have to tell you something about Python's scope rules. Class definitions play some neat tricks with namespaces, and you need to know how scopes and namespaces work to fully understand what's going on. Incidentally,…

原文地址:http://nootrix.com/2013/08/ros-namespaces/   In this tutorial, we will be talking about ROS namespaces which allow to combine nodes in ways unplanned by developers. This is actually what all ROS is about: allow building systems by connecting nod…

Namespaces In most programming languages we know the concept of namespaces (or packages).Namespaces allow us to group code and help us to avoid name-collisions. In c# for example you have this declaration ? namespace MyNameSpace {     public class My…

User namespaces – available to play! Posted on May 10, 2012by s3hh Over the past few months, Eric Biederman has been working on completing the user namespace. Briefly, unprivileged users can create a user namespace, where he can pretend to be root an…

本文出处:http://www.cnblogs.com/wy123/p/6238844.html 最近遇到一个存储过程在某些特殊的情况下,效率极其低效, 至于底下到什么程度我现在都没有一个确切的数据,因为预期很快就可以查询出来结果的SQL,实则半个小时都出不来,后面会有截图 观察执行计划的时候发现中间有一步中出现一个类似如下非常规的连接提示警告,如下图 no join predicate 意思就是没有连接谓词,表之间join的时候没有指定连接谓词可以导致no join predicate, 但是…

启动tomcat, 出现, ( 之前都是好好的... ) [lk ] ERROR [08-12 15:10:02] [main] org.springframework.web.context.ContextLoader.initWebApplicationContext(215) | Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean…

nested loops join(嵌套循环)   驱动表返回几条结果集,被驱动表访问多少次,有驱动顺序,无须排序,无任何限制. 驱动表限制条件有索引,被驱动表连接条件有索引. hints:use_nl() merge sort join(排序合并)   驱动表和被驱动表都是最多访问1次,无驱动顺序,需要排序(SORT_AREA_SIZE),连接条件是<>或like导致无法使用. 在连接条件上建立索引可以消除一张表的排序. hints:use_merge() hash join(哈希连接)  …

Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Different from the previous question where weight…

Given a nested list of integers, implement an iterator to flatten it. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Example 1: Given the list [[1,1],2,[1,1]], By calling next repeatedly until hasN…

Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Example 1: Given the list [[1,1],2,[1,1]], return…

禁用nested loop join里的spool 转载自: https://blogs.msdn.microsoft.com/psssql/2015/12/15/spool-operator-and-trace-flag-8690/ https://answers.sqlperformance.com/questions/698/lazy-spool.html 在nested loop join里常常会看到一个spool操作符 这个spool 又名'performance spool',目的是…

嵌套Fragment的使用及常见错误 嵌套Fragments (Nested Fragments), 是在Fragment内部又添加Fragment. 使用时, 主要要依靠宿主Fragment的 getChildFragmentManager() 来获取FragmentManger. 虽然看起来和在activity中添加fragment差不多, 但因为fragment生命周期及管理恢复模式不同, 其中有一些需要特别注意的地方. 本文内容还包括了从Fragment迁移到v4.Fragment代码中…

转自http://blog.itpub.net/22664653/viewspace-1692317/ 一 介绍  相信许多开发/DBA在使用MySQL的过程中,对于MySQL处理多表关联的方式或者说性能一直不太满意.对于开发提交的含有join的查询,一般比较抗拒,从而建议将join拆分,避免join可能带来的性能问题,同时也增加了程序和DB的网络交互.5.5 版本之前,MySQL本身只支持一种表间关联方式,就是嵌套循环(Nested Loop).如果关联表的数据量很大,则join关联的执行时间…

原题链接在这里:https://leetcode.com/problems/nested-list-weight-sum/ 题目: Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers…

ssh项目启动报错: org.dom4j.DocumentException: Connection timed out: connect Nested exception: Connection timed out: connect 一开始以为是数据库连接的事,后来发现是hibernate在实体对象映射数据库表的时候出的错 解决: 查看hibernate.jar包里的hibernate-mapping-3.0.dtd里的 <!DOCTYPE hibernate-mapping PUBLIC &qu…

贴出applicationContext.xml <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://ww…

目前为止,典型的连接类型有3种: Sort merge join(SMJ排序-合并连接):首先生产driving table需要的数据,然后对这些数据按照连接操作关联列进行排序:然后生产probed table需要的数据,然后对这些数据按照与driving table对应的连接操作列进行排序:最后两边已经排序的行被放在一起执行合并操作.排序是一个费时.费资源的操作,特别对于大表.所以smj通常不是一个特别有效的连接方法,但是如果driving table和probed table都已经预先排序,…

题目要求: (**) Flatten a nested list structure. Example: scala> flatten(List(List(1, 1), 2, List(3, List(5, 8)))) res0: List[Any] = List(1, 1, 2, 3, 5, 8) 参考:http://blog.thedigitalcatonline.com/blog/2015/04/07/99-scala-problems-07-flatten/#.WBsDFPl97IU 针…

org.dom4j.DocumentException : 1 字节的 UTF-8 序列的字节 1 无效. Nested exception: 1 字节的 UTF-8 序列的字节 1 无效. 网上查了一下  都说是什么改下文件编码,就想万一在服务器上的文件怎么改编码,应该会有设置编码的地方,找了一下果然有 SAXReader saxReader = new SAXReader(); saxReader.setEncoding("GB2312");//这里设置文件编码 document…

SSH框架出现了下面的错误: nested exception is org.hibernate.QueryException: could not resolve property 检查了hbm.xml文件无误,后来才发现是查询语句的属性名大小写搞错了.…

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'daoSupport': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name…

转载:http://blog.csdn.net/ysdaniel/article/details/7043395 出现 Error #include nested too deeply 原因是: 头文件相互包含. 例如,一个工程中bsp.h 包含 LocDongle.h, LocDongle.h又包含bsp.h, 编译时就会报Error #include nested too deeply . 解决办法: 1.将两个头文件共用的那一部分抽出来单独建一个头文件. 2.加预处理#ifndef.. #…

Given a nested list of integers, implement an iterator to flatten it. Each element is either an integer, or a list -- whose elements may also be integers or other lists. ExampleGiven the list [[1,1],2,[1,1]], By calling next repeatedly until hasNext…

Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Different from the previous question where weight…

通过代码创建了索引名称为demoindex,索引类型为school,以下是索引类型的数据映射结构: { "state": "open", "settings": { "index.number_of_replicas": "1", "index.number_of_shards": "5", "index.version.created": &qu…

Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Example 1:Given the list [[1,1],2,[1,1]], return…

异常信息如下: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.util.Date' to required type 'java.sql.Timestamp' for property 'wfsj'; nested exception is java.lang.IllegalStateException: Cannot conver…

在.NET程序编写中,需要using相应命名空间或添加相应的References,可有时候没有使用到的命名空间也被添加到了Using Namespaces中,那么,这样会影响程序的执行效率么? 通过示例说明: 新建一Windows 控制台应用程序(基于.NET Framework 2.0)后项目代码里自动会添加 using System; using System.Collections.Generic; using System.Text; 三项命名空间的引用. 同时,在项目中的“引用”中自动…

有时我们需要动态生成一些模块名,然后调用它里面的函数.但是我们常常碰到的却是明明有那个模块,结果还是raise模块未定义... 我们来看看到底怎么回事? 首先我们定义一个函数 iex(1)> defmodule Science.Math do ...(1)> def add(x,y) do ...(1)> x + y ...(1)> end ...(1)> end 当我们正常调用它是,是没有问题的: iex(2)> Science.Math.add 1,2 3 但是 i…