JDK源码一句注释: c.toArray might (incorrectly) not return Object[] (see 6260652)

Mar 04,2017 in Java read (779)

ArrayList的构造方法中有这样一句注释: public ArrayList(Collection<? extends E> c) { elementData = c.toArray(); size = elementData.length; /...

Hadoop 底层通信(八)

Mar 04,2017 in Hadoop read (802)

IPC和RPC IPC:进程间通信 RPC:remote procedure call,远程过程调用 Socket:套接字编程 Socket:客户端套接字 ServerSocket:服务器端 nio:异步通信 Channel Selector hadoop底层通信,使用Go...

Mar 01,2017 in Java read (798)

使用JDBC时，我们都会很自然得使用下列语句: Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://127.0.0.1/test?useUnicode=true&characte...

Feb 27,2017 in Linux read (1187)

Exit codes and kill-job signals 退出代号和杀死作业的信号 The exit code from a batch job is a standard Unix termination status, the same sort of numbe...

Feb 27,2017 in Hadoop,大数据 read (948)

1. mkdir: Permission denied 原因:使用hadoop fs -mdkir /xxx/xxx创建文件路径时,出现权限问题 1.使用hdfs这个用户登录 sudo -uhdfs hadoop fs -mdkir /xxx/xxxx 2.通过hdfs用户...

Feb 24,2017 in Hadoop read (921)

Yarn框架底层事件分发原理 hadoop yarn调度框架调度mr作业基于事件 job 对应application applicatio基于状态机模型,后台web页面Applications下面的每个标签对应一种状态,有 new new saving subm...

Feb 21,2017 in Hive read (1980)

hdfs更改权限:sudo -u hdfs hadoop fs -chown carpo:hdfs /apps/carpo show databases; use tpcds_orc; show tables; drop table tpcds_orc; create ta...

Feb 21,2017 in Oracle read (1173)

ORA-01861: 文字与格式字符串不匹配可能是插入字符串没加引号,或插入时间直接按字符串插入,使用to_date函数转换一下就可以了,例如:to_date('2003-01-02','yyyy-mm-dd') ORA-00911: 无效字符存在中文标点,或把字符串当...