小编use*_*504的帖子

例如,我在MongoDB中有以下数据:

{ "_id" : ObjectId("524091f99c49c4c3f66b0e46"), "hour" : 10, "incoming", 100}
{ "_id" : ObjectId("5240a045dbeff33c7333aa51"), "hour" : 11, "incoming", 200}
{ "_id" : ObjectId("5240a2ecda0d37f35c618aca"), "hour" : 12, "incoming", 300}

现在我想查询"SUM 11到12之间传入的数量"(结果应该是500),我怎么能用Mongo Shell做到这一点？

我正在尝试在服务器上安装Hadoop 2.2.0群集.目前所有服务器都是64位,我下载Hadoop 2.2.0并且已经设置了所有配置文件.当我运行./start-dfs.sh时,我收到以下错误:

13/11/15 14:29:26 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Starting namenodes on [Java HotSpot(TM) 64-Bit Server VM warning: You have loaded library /home/hchen/hadoop-2.2.0/lib/native/libhadoop.so.1.0.0 which might have disabled stack guard. The VM will try to fix the stack guard now.It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.namenode]
sed: -e expression #1, char 6: unknown option to `s' have: ssh: Could …

我现在正在学习如何使用Hadoop Pig.

如果我有这样的输入文件:

a,b,c,true
s,c,v,false
a,s,b,true
...

最后一个字段是我需要计算的字段...所以我想知道这个文件中有多少'true'和'false'.

我尝试:

records = LOAD 'test/input.csv' USING PigStorage(',');
boolean = foreach records generate $3;
groups = group boolean all;

现在我卡住了.我想用:

count = foreach groups generate count('true');" 

要获得"真实"的数量,但我总是得到错误:

2013-08-07 16:32:36,677 [main] ERROR org.apache.pig.tools.grunt.Grunt - 错误1070:无法使用导入解析计数:[,org.apache.pig.builtin.,org.apache .pig.impl.builtin.]日志文件的详细信息:/etc/pig/pig_1375911119028.log

谁能告诉我问题出在哪里？

例如,我想编写一个Java程序,在每天上午12点打印"Hello World",如何使用Quartz调度程序来实现这一目标？

Trigger trigger = TriggerUtils.makeDailyTrigger(0, 0);
trigger.setName("trigger1");
trigger.setGroup("group1");

像这样？我应该在哪里打印"hello world"方法？

现在我正在学习HBase.我设置了我的HBase集群和Hadoop集群,如下所示:

server1: Namenode HMaster
server2: datanode1 RegionServer1 HQuorumPeer
Server3: datanode2 RegionServer2 HQuorumPeer
Server4: datanode3 RegionServer3 HQuorumPeer

我有几个关于HBase集群的问题:

1: All RegionServers must be in the Hadoop Cluster so it can use HDFS to store 
   data, even though it will store data into local file system, right?
2: What does RegionServer do? Does the HMaster give the job to all RegionServeres 
   and let them running parallel, like tasktracker in datanode? 
3: What does zookeeper do? Do I need to setup zookeeper in …

我有一些关于 HBase Shell 命令工具的问题：

1: How to list all column family names (just names!) in a table?
2: How to count the number of rows in a column family?

我有一个字符串，我正在尝试将空格替换为换行符

我原来的字符串

xxx xxx xxx xxx

如果我使用以下命令，则它可以工作

echo $string | sed 's/ /\n/g'

但是，如果我想将新字符串分配给另一个变量，例如

newString=`echo $string | sed 's/ /\n/g'`
echo $newString

它不起作用...

有谁知道为什么？