在未安装 mongo 的机器上执行 Mongo mapreduce 作业
我有一组需要从 Java 程序执行的 MapReduce 作业。现在我正在通过 Java 进程调用执行它们
$MONGO_HOME/bin/mongo host:port/database jsFiles
是否有一种方法可以在没有 Mongo 的机器上执行这些 MapReduce 任务。 mongo Java 驱动程序支持此类功能吗？
谢谢！
I have a set of mapreduce jobs which I need to execute from my Java program. Right now I am executing them via a Java Process calling
$MONGO_HOME/bin/mongo host:port/database jsFiles
Is there a way I could execute these mapreduce taks on a machine which does not have Mongo. Does the mongo Java driver support such functionality ?
Thanks!
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MongoDB MapReduce 作业始终在 Mongo 服务器上运行，而不是在客户端中运行，任何客户端都可以将作业发送到服务器。
@Chris Shain 向您指出了文档（http://api.mongodb.org/java/current/com/mongodb/MapReduceCommand.html），我建议您阅读它们，但也要了解大多数 MapReduce 操作都是关于将数据库中存储的大量数据减少为较小的结果集。离数据实际存储的位置越近越好，而且大多数人不会直接在服务器上执行命令。为了使 MapReduce 操作发挥作用，Mongo 必须（并且确实如此！）提供一种从客户端使用它的方法。对于一般策略，请参见此处： http://www.mongodb.org/display/DOCS/MapReduce< /a>
请注意，由于该操作在服务器上运行，因此您可能会注意到锁定百分比有所增加。如果这对您来说是个问题，请考虑在从属或辅助 Mongo 实例上运行 MapReduce 作业。
MongoDB MapReduce jobs are always run on the Mongo server, never in the client, and any client can send a job to the server.
@Chris Shain pointed you to the docs (http://api.mongodb.org/java/current/com/mongodb/MapReduceCommand.html), and I recommend you read them, but also understand that most MapReduce operations will be all about reducing the huge volumes of data stored into your database down to smaller result sets. The closer this is done to where the data is actually stored, the better, and most people do not execute commands directly on the server. In order for the MapReduce operation to be useful, Mongo would have to (and did!) provide a way to use it from the client. For general strategies, see here: http://www.mongodb.org/display/DOCS/MapReduce
Note that because the operation runs on the server, you may notice increased lock percentage. Consider running the MapReduce job on a slave or secondary Mongo instance if this is a problem for you.
Mongo 的 Java 客户端驱动程序具有 MapReduceCommand，记录如下： http:// api.mongodb.org/java/current/com/mongodb/MapReduceCommand.html
The Java client driver for Mongo has the MapReduceCommand, documented here: http://api.mongodb.org/java/current/com/mongodb/MapReduceCommand.html