MongoDB mapreduce而不是聚合

时间:2018-10-15 09:27:45

标签: javascript java mongodb mapreduce

我是mongodb中MR职位的新手。我有一个聚合函数,如下所示:

db.acollection.aggregate([{$match:{ "userId" : { "$eq" : "raghu" }}}, 
{$group:{ "_id" : { "region":"$region", "shipMode" : "$shipMode"}, "sales" : { "$sum" : "$sales"}}}, 
{"$sort" : { "_id.region" : 1, "sales" : 1 }}, { "$limit" : 1000}]);

由于性能问题,参考:search_field_tag我正在创建MRjob。因此,我应该获取Map中所有相关的文档,而Reduce中的所有文档应该分别为groupbysortlimit。我有如下功能:

final MongoDatabase mongoDatabase = MongoUtils.getMongoDatabase(model);
BasicDBObject obj = pipeline.get(1);
MapReduceIterable<Document> list = mongoDatabase.getCollection(collectionName).mapReduce(getMapFunction(obj.getString("userId")), getReduceFunction());
// the above code is the main call but am mostly thinking about the map and reduce functions.

private String getMapFunction(String whereCondition) {

StringBuilder map= new StringBuilder();
map.append("function() {"
        + "var key=whereCondition;"
        + "if(this.userId==key)"
// how to get all the documents for this key ?
        + "}");
}


    private String getReduceFunction() {

        String reduce="";
// what should go here ?
        return reduce;
    }

不确定如何获得JavaScript代码,我想发出完整的JSON对象作为值,以便我可以将其映射化。像这样:

private String getMapFunction() {

//somecode here and then finally ..
  emit(this.tenantId_V, object);
}

0 个答案:

没有答案