我有一个聚合查询,如下所示:
db.TWITTER_DATA_Processed.aggregate( {$match : { SpId : 840, Scheduler_id : "SCH_01" }},{$group : {_id : {SpId : "$SpId", Scheduler_id : "$Scheduler_id",Country : "$Country"}, positive_count : { $sum: { $cond: [ { $gt: [ "$Sentiment", 0 ] } , 1, 0 ] } }, neutral_count : { $sum: { $cond: [ { $eq: [ "$Sentiment", 0 ] } , 1, 0 ] } }, negative_count : { $sum: { $cond: [ { $lt: [ "$Sentiment", 0 ] } , 1, 0 ] } }}})
示例输出:
{
"_id" : {
"SpId" : 840,
"Scheduler_id" : "SCH_01",
"Country" : "Argentina"
},
"positive_count" : 1,
"neutral_count" : 2,
"negative_count" : 0
},
{
"_id" : {
"SpId" : 840,
"Scheduler_id" : "SCH_01",
"Country" : "United Kingdom"
},
"positive_count" : 17,
"neutral_count" : 4,
"negative_count" : 1
}
由于$ cond运算符,我在编写相同的java代码时遇到了困难。从现有的线程中,我假设$ gt必须写成如下:
DBObject positiveSentiment = new BasicDBObject("$Sentiment", new BasicDBObject("$gt", 0));
我唯一可以弄清楚$ cond的是它需要一个操作数数组(在我的实验中,我得到了以下错误:
"errmsg" : "exception: the $cond operator requires an array of 3 operands" , "code" : 16019
但我如何适合
[{$ gt:[“$ Sentiment”,0]},1,0]
在Java代码中?
添加最终的工作代码,以防将来有人需要参考:
DBObject groupIdKeys = new BasicDBObject("SpId", "$SpId");
groupIdKeys.put("Scheduler_id", "$Scheduler_id");
groupIdKeys.put("Country", "$Country");
/* positive sentiments */
List<Object> gtOperands = new ArrayList<Object>();
gtOperands.add("$Sentiment");
gtOperands.add(0);
List<Object> positiveCondOperands = new ArrayList<Object>();
positiveCondOperands.add(new BasicDBObject("$gt", gtOperands));
positiveCondOperands.add(1);
positiveCondOperands.add(0);
BasicDBObject finalPositiveCond = new BasicDBObject("$cond",
positiveCondOperands);
DBObject sumOfPositiveCount = new BasicDBObject("$sum",
finalPositiveCond);
/* neutral sentiments */
List<Object> eqOperands = new ArrayList<Object>();
eqOperands.add("$Sentiment");
eqOperands.add(0);
List<Object> neutralCondOperands = new ArrayList<Object>();
neutralCondOperands.add(new BasicDBObject("$eq", eqOperands));
neutralCondOperands.add(1);
neutralCondOperands.add(0);
BasicDBObject finalNeutralCond = new BasicDBObject("$cond",
neutralCondOperands);
DBObject sumOfNeutralCount = new BasicDBObject("$sum", finalNeutralCond);
/* negative sentiments */
List<Object> ltOperands = new ArrayList<Object>();
ltOperands.add("$Sentiment");
ltOperands.add(0);
List<Object> negativeCondOperands = new ArrayList<Object>();
negativeCondOperands.add(new BasicDBObject("$lt", ltOperands));
negativeCondOperands.add(1);
negativeCondOperands.add(0);
BasicDBObject finalNegativeCond = new BasicDBObject("$cond",
negativeCondOperands);
DBObject sumOfNegativeCount = new BasicDBObject("$sum",
finalNegativeCond);
DBObject groupKeys = new BasicDBObject("_id", groupIdKeys);
groupKeys.put("positive_count", sumOfPositiveCount);
groupKeys.put("neutral_count", sumOfNeutralCount);
groupKeys.put("negative_count", sumOfNegativeCount);
DBObject group = new BasicDBObject("$group", groupKeys);
AggregationOutput output = dbCollection.aggregate(firstOp, group);
Iterable<DBObject> results = output.results();
for (DBObject result : results) {
System.out.println(result);
}
答案 0 :(得分:3)
按照示例here,您可以为“$ cond”运算符创建数组,如下所示:
ArrayList gtA = new ArrayList();
gtA.add("$Sentiment");
gtA.add(0);
ArrayList condArray = new ArrayList();
condArray.add(new BasicDBObject("$gt", gtA));
condArray.add(1);
condArray.add(0);
BasicDBObject fullCond = new BasicDBObject("$cond", condArray);