I am trying to fetch the data from the MongoDB to get the top 5 most liked products.
But I'm getting below error. (MongoDB version 3.2.21)
com.mongodb.MongoCommandException: Command failed with error 9: 'The 'cursor' option is required, except for aggregate with the explain argument' on server localhost:27017. The full response is { "ok" : 0.0, "errmsg" : "The 'cursor' option is required, except for aggregate with the explain argument", "code" : 9, "codeName" : "FailedToParse" }
DBObject groupFields = groupFields = new BasicDBObject("_id", 0);
groupFields.put("_id", "$productId");
groupFields.put("avgRating", new BasicDBObject("$avg", "$productRvR"));
groupFields.put("productModelName", new BasicDBObject("$push", "$productMN"));
DBObject group = new BasicDBObject("$group", groupFields);
DBObject projectFields = new BasicDBObject("_id", 0);
projectFields.put("productId", "$_id");
projectFields.put("avgRating", "$avgRating");
projectFields.put("productModelName", "$productModelName");
DBObject project = new BasicDBObject("$project", projectFields);
DBObject sort = new BasicDBObject();
sort.put("avgRating",-1);
DBObject orderby=new BasicDBObject("$sort",sort);
DBObject limit=new BasicDBObject("$limit",5);
AggregationOutput aggregate userReviews.aggregate(group,project,orderby,limit);
LinkedHashMap<String, String> mostLikedProductsMap = new LinkedHashMap<String, String>();
for (DBObject queryResult : aggregate.results()) {
BasicDBObject obj = (BasicDBObject) queryResult;
BasicDBList productModelName = (BasicDBList) obj.get("productModelName");
mostLikedProductsMap.put((String)productModelName.get(0),obj.getString("avgRating"));
}
return mostLikedProductsMap;
Related
I'd like to learn how to implement group by query using Mongo DB Java 3.x Driver. I want to group my collection through the usernames, and sort the results by the count of results DESC.
Here is the shell query which I want to implement the Java equivalent:
db.stream.aggregate({ $group: {_id: '$username', tweetCount: {$sum: 1} } }, { $sort: {tweetCount: -1} } );
Here is the Java code that I have implemented:
BasicDBObject groupFields = new BasicDBObject("_id", "username");
// count the results and store into countOfResults
groupFields.put("countOfResults", new BasicDBObject("$sum", 1));
BasicDBObject group = new BasicDBObject("$group", groupFields);
// sort the results by countOfResults DESC
BasicDBObject sortFields = new BasicDBObject("countOfResults", -1);
BasicDBObject sort = new BasicDBObject("$sort", sortFields);
List < BasicDBObject > pipeline = new ArrayList < BasicDBObject > ();
pipeline.add(group);
pipeline.add(sort);
AggregateIterable < Document > output = collection.aggregate(pipeline);
The result I need is the count of documents grouped by username. countOfResults returns the total number of the documents the collection has.
You should try not to use old object (BasicDBObject) types with Mongo 3.x. You can try something like this.
import static com.mongodb.client.model.Accumulators.*;
import static com.mongodb.client.model.Aggregates.*;
import static java.util.Arrays.asList;
Bson group = group("$username", sum("tweetCount", 1));
Bson sort = sort(new Document("tweetCount", -1));
AggregateIterable <Document> output = collection.aggregate(asList(group, sort));
I wonder how to perform the aggregation $match on a $lookup collection with the java driver for mongodb 3.2. Here is the structure of the two collections i am working on :
coll_one:{
_id : ObjectId("hex_string"),
foreign_id : ObjectId("hex_string") **the id of coll_two**}
coll_two:{
_id : ObjectId("hex_string"),
actif : true,
closed : false }
The lookup on the two ids (coll_one.foreign_id & coll_two._id) seems to work fine. But when i specify a match on coll_two.actif = true, it returns an empty result.
This is the Java code i'am using :
Bson lookup = new Document("$lookup",
new Document("from", "coll_two" )
.append("localField", "foreign_id")
.append("foreignField", "_id")
.append("as", "look_coll"));
List<Bson> filters = new ArrayList<Bson>();
filters.add(lookup);
//here is the MATCH
filters.add(match(eq("look_coll.actif",true)));
DB().getCollection("coll_one").aggregate(filters);
Evrything works fine whene i remove the match section. I have tried so many combination of possibilities with no success at all !!!
Can any body tells me if this is possible ????
Add your $match request to a Document instance :
Bson match = new Document("$match",
new Document("look_coll.actif", true));
filters.add(match);
Here is a full example :
MongoClient mongoClient = new MongoClient("localhost");
MongoDatabase db = mongoClient.getDatabase("mydb");
Bson lookup = new Document("$lookup",
new Document("from", "coll_two")
.append("localField", "foreign_id")
.append("foreignField", "_id")
.append("as", "look_coll"));
Bson match = new Document("$match",
new Document("look_coll.actif", true));
List<Bson> filters = new ArrayList<>();
filters.add(lookup);
filters.add(match);
AggregateIterable<Document> it = db.getCollection("coll_one").aggregate(filters);
for (Document row : it) {
System.out.println(row.toJson());
}
How to write this mongodb shell query with using java?
query : db.building_feature.find({geometry : {$geoIntersects :{$geometry :{type : "Polygon", coordinates :[[[37.59777,55.73216],[37.59805,55.77615],[37.68710,55.77643],[37.68517,55.73290],[37.59777,55.73216]]]}}}})
My collection GeoSpatialIndex is "2dsphere".
My version which is not working :
DBCollection testCollection = db.getCollection("building_feature");
final LinkedList<double[]> geo = new LinkedList<>();
geo.addLast(new double[]{37.59777, 55.73216});
geo.addLast(new double[]{37.59805, 55.77615});
geo.addLast(new double[]{37.68710, 55.77643});
geo.addLast(new double[]{37.68517, 55.73290});
final BasicDBObject query
= new BasicDBObject("geometry", new BasicDBObject("$within", new BasicDBObject("$geometry", geo)));
System.out.println("Result Count : " + testCollection.find(query).count());
Thanks.
You should write exactly the same query in Java:
BasicDBObject polygon = new BasicDBObject("type", "Polygon");
polygon.put("coordinates", <myArray>);
BasicDBObject query = new BasicDBObject(
"geometry", new BasicDBObject(
"$geoIntersects", new BasicDBObject(
"$geometry", polygon
)
)
);
<myArray> being your triple-nested double[][][] geoJSON polygon coordinates array.
Btw, it could be more clear to read with a JSON string and then JSON.parse.
And I think $whithin operator does not exist in MongoDB...
i need to use mongodb java aggregate function to detect duplicated documents in collection, this is the query i ran from command line and it worked:
db.placements.aggregate(
{$group:{ "_id: "$campaign", total:{$sum:1}}},
{$match: {total: {$gt:2}}},
{$limit:10},
{$skip:0}
);
and this is the java code i wrote:
DBObject groupFields = new BasicDBObject("_id", "$campaign");
groupFields.put("total", new BasicDBObject("$sum", 1));
DBObject group = new BasicDBObject("$group", groupFields);
DBObject matchFields = new BasicDBObject("total", new BasicDBObject("$gt", 2));
DBObject match = new BasicDBObject("$match", matchFields);
collection.aggregate(match, group, new BasicDBObject("$skip", 0), new BasicDBObject("$limit", 10));
but it always return empty result. can anyone tell me what's wrong?
I have a collection.
look
{ "_id" : 13.0 , "tenantref" : { "$id" : 3.0}}
I need to retrieve the value of id 3.0 using java.
I am getting null pointer exception.
BasicDBObject field = new BasicDBObject();
BasicDBObject field = new BasicDBObject();
field.put("tenantref.$id", 1);
DBCursor cursor = mongo.getDB("number").getCollection("testthree").find(query,field);
while (cursor.hasNext())
{
System.out.println(cursor.next().get("tenantref.$id"));
}
I am getting null pointer exception. How do I need to get the value?
cursor.next().get("tenantref.$id"));
The get() function of BasicDBObject does not support the dot syntax. You have to traverse the object hierarchy by hand. Try
((DBObject)cursor.next().get("tenantref")).get("$id");