java在MongoDB中使用MapReduce时出错
首先,我使用操作系统windows XP 32位,MongoDB作为NoSQL DB,Eclipse作为编辑器程序。我收到了学校关于MapReduce的作业,所以我决定找出有多少工作年龄和非工作人口在使用MapReduce。我使用这些代码输入数据并保存为Insert。爪哇:
package mongox;
import com.mongodb.BasicDBObject;
import com.mongodb.Mongo;
import com.mongodb.DB;
import com.mongodb.DBCollection;
public class Insert {
public static void main(String[] args) {
try{
Mongo mongox = new Mongo();
DB db = mongox.getDB("DBPublic");
DBCollection koleksi = db.getCollection("lancestorvalley");
BasicDBObject object = new BasicDBObject();
object = new BasicDBObject();
object.put("NIK", "7586930211");
object.put("Name", "Richard Bou");
object.put("Sex", "M");
object.put("Age", "31");
object.put("Blood", "A");
object.put("Status", "Married");
object.put("Education", "Bachelor degree");
object.put("Employment", "Labor");
koleksi.insert(object);
}
catch(Exception e){
System.out.println(e.toString());
}
}
}
我将此代码用于MapReduce并另存为MapReduce。爪哇:
package mongox;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.MapReduceCommand;
import com.mongodb.MapReduceOutput;
import com.mongodb.Mongo;
public class Mapreduce {
public static void main(String[] args) {
try{
Mongo mongox = new Mongo("localhost", 27017);
DB db = mongox.getDB("DBPublic");
DBCollection koleksi = db.getCollection("lancestorvalley");
String map = "function() { "+
"var category; " +
"if ( this.Age >= 15 && this.Age <=59 ) "+
"category = 'Working-Age Population'; " +
"else " +
"category = 'Non-Working-Age Population'; "+
"emit(category, {Nama: this.Nama});}";
String reduce = "function(key, values) { " +
"var sum = 0; " +
"values.forEach(function(doc) { " +
"sum += 1; "+
"}); " +
"return {data: sum};} ";
MapReduceCommand cmd = new MapReduceCommand(koleksi, map, reduce,
null, MapReduceCommand.OutputType.INLINE, null);
MapReduceOutput out = koleksi.mapReduce(cmd);
for (DBObject o : out.results()) {
System.out.println(o.toString());
}
}
catch(Exception e){
e.printStackTrace();;
}
}
}
我已经输入了5000个数据,当我运行Mapreduce时。java输出为:
{ "_id" : "Non-Working-age population" , "value" : { "data" : 41.0}}
{ "_id" : "Working-age Population" , "value" : { "data" : 60.0}}
我在Mapreduce中的代码有问题吗。JAVA为什么数据在5000左右时,输出结果只有这样? 希望有人能帮我,谢谢大家
# 1 楼答案
MongoDB文档明确说明了以下可能是导致意外行为的原因:
此外: