一般来说，报`native snappy library not available: this version of libhadoop was built without snappy support.`,其在应用启动时会有个WARN信息`Unable to load native-hadoop library for your platform... using builtin-java
2018-06-29 10:20:46
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```java
abstract public class FsCommand extends Command {
/**
* Register the command classes used by the fs subcommand
* @param factory where to register the class
*/
public static void
# pv命令用法
监测数据流的速率、用时、进度
还支持对数据进行限速
## 安装
To use the YUM repository, add this to your /etc/yum.conf or(on Fedora Core 4 and above) to /etc/yum.repos.d/ivarch.repo:
```
[ivarch]
name=RPMs from ivarc
2018-04-19 11:17:19
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## 配置
创建一个exclude文件，里面添加要移除节点的ip或hostname，每行一个。如我的是`vim /etc/emr/hadoop-conf/exclude`,文件添加
```
emr-worker-3
emr-worker-4
emr-worker-5
```
`hdfs-site.xml`添加
```
dfs.hosts.exclude
/etc/emr
2018-04-16 17:01:35
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## 介绍
> The Web Application Proxy is part of YARN. By default it will run as part of the Resource Manager(RM), but can be configured to run in stand alone mode. The reason for the proxy is to reduce
2018-03-30 16:33:06
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## 总览
### 文法文件经过ANTLR编译后的产物
### ANTLR使用流程
### Linux 安装、配置
1. 下载antlr4 二进制包，并解压到某目录，该目录
当需要合并多路的数据到同一张表中时，如果用到了`union all`语句,那么会提高sql的执行复杂度。可以通过增加冗余分区来简化sql复杂度，提高并行度
2018-03-27 09:36:30
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# 软件设计原则
## 单一职责原则
> Single Responsibility Principle, 简称SRP。
老美的定义是这样的
> A class should have only one reason to change
> 一个类改变它的原因有且只能是一个
跑union all 语句时会多出一层目录，是tez在当前环境下的一个坑，导致其他的计算框架取不到数据