How to write multiple group by id fields in Mongodb java driver

Question

In the below query

{ $group : {
        _id :  { success:'$success', responseCode:'$responseCode', label:'$label'},
        max_timeStamp : { $timeStamp : 1 },
        count_responseCode : { $sum : 1 },
        avg_value : { $sum : "$value" },
        count_success : { $sum : 1 }
    }}

How _id : { success:'$success', responseCode:'$responseCode', label:'$label'}, can be translated to use in java mongodb driver.

I tried

BasicDBList list = new BasicDBList();
list.add(new BasicDBObject("success", "$success"));
list.add(new BasicDBObject("responseCode", "$responseCode"));
list.add(new BasicDBObject("label", "$label"));
AggregationOutput output = collection.aggregate(match, project, group);

and

Multi-dimension array

String [][] muitiGroupBy = {{"success", "$success"},{"responseCode", "$responseCode"},{"label", "$label"}};

etc..

But i always get like this as result

"_id" : [ { "success" : "$success"} , { "responseCode" : "$responseCode"}]

If I use only one field it works.

DBObject groupFields = new BasicDBObject( "_id", new BasicDBObject("success", "$success"));

zerpsed · Accepted Answer · 2018-09-05 20:22:44Z

9

I had a similar need and titogeo's answer from 2013 led me in the right direction after many failed attempts to translate my aggregation operation into something the Java client could handle. This is what I used:

MongoCollection<Document> myCollection = myDB.getCollection("myCollection");

Map<String, Object> multiIdMap = new HashMap<String, Object>();
multiIdMap.put("groupField1", "$groupField1");
multiIdMap.put("groupField2", "$groupField2");

Document groupFields = new Document(multiIdMap);
AggregateIterable<Document> aggregate = myCollection.aggregate(Arrays.asList(
        Aggregates.group(groupFields,
                Accumulators.last("lastDate", "$dateCreated"),
                Accumulators.last("lastNumAvail", "$availableUnits")
                )
        ));

I got back exactly what I needed to match the result from this:

db.myCollection.aggregate([
            {"$group":{ "_id":{
                groupField1: "$groupField1", 
                groupField2: "$groupField2"}, 
                lastDate: 
                    {"$last":"$dateCreated"}, 
                lastNumAvail: 
                    {"$last":"$availableUnits"}
                }
               }                
            ]);

answered Sep 5, 2018 at 20:22

zerpsed

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2 Comments

ionised Over a year ago

You're a an absolute star for this answer, thank you! I've been upgrading an aging tech stack's MongoDB from 3.4 to 6.0 and all of our client code was written in GMongo format which needed to be replaced. I couldn't for the life of my figure out how to do multiple group fields in the Java Sync Driver API like this. I spent days looking for a solution until I happened your answer. Cheers!

zerpsed Over a year ago

@ionised, wow, thank you so much for the feedback. I'm real happy to have helped you out. Good luck with your stack upgrade!

titogeo · Accepted Answer · 2013-03-25 07:06:20Z

6

We did figure out how. We can achieve by using this.

Map<String, Object> dbObjIdMap = new HashMap<String, Object>();
dbObjIdMap.put("success", "$success");
dbObjIdMap.put("responseCode", "$responseCode");
dbObjIdMap.put("label", "$label");
DBObject groupFields = new BasicDBObject( "_id", new BasicDBObject(dbObjIdMap));

answered Mar 25, 2013 at 7:06

titogeo

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Comments

Cassio Landim · Accepted Answer · 2016-03-05 19:56:55Z

0

I could achieve this through this code (grails code and mongo-java-driver-3.2):

DBObject groupFields = new BasicDBObject()
groupFields.put('success', "\$success")
groupFields.put('responseCode', "\$responseCode")
groupFields.put('label', "\$label")
def result = collection.aggregate(Arrays.asList(Aggregates.group(groupFields, []))).iterator()

edited Mar 5, 2016 at 19:56

answered Mar 5, 2016 at 19:48

Cassio Landim

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1 Comment

Paul Over a year ago

With Java driver 3+ the Document class should be used instead of BasicDBObject.

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