mongodb issue in java with limit and sort

Question

Collection:progs

{ "_id" : "ABC", "defaultDirectory" : "abc", "defaultRecvDirectory" : "abc" }
{ "_id" : "RAS", "defaultRecvDirectory" : "recv/ras" }
{ "_id" : "SND", "defaultSendDirectory" : "send/snd" }

In the mongo console:

db.progs.find({"_id":{"$lt":"ZZZZZZZZZ"}}).sort({"_id":-1}).limit(1);

==>    { "_id" : "SND", "defaultSendDirectory" : "send/snd" }

In Java:

    BasicDBObject query = new BasicDBObject();
    query.put("_id", new BasicDBObject("$lt", "ZZZZZZZZZZ"));
    DBCursor cursor = collection.find(query).sort(new BasicDBObject("_id","-1")).limit(1);
    for (DBObject dbObject : cursor) {
        System.out.println(dbObject);
    }

==>    { "_id" : "ABC", "defaultSendDirectory" : "abc", "defaultRecvDirectory" : "abc" }

Someone can explain the difference?

redochka · Accepted Answer · 2018-08-13 07:38:27Z

27

Remove the quotes from the "-1" in your sort:

DBCursor cursor = collection.find(query).sort(new BasicDBObject("_id",-1)).limit(1);

Or use Mongodb ASC/DESC constants from com.mongodb.operation.OrderBy instead of hardcoding 1 / -1

Example:

DBCursor cursor = collection.find(query).sort(new BasicDBObject("_id", OrderBy.DESC.getIntRepresentation())).limit(1);

edited Aug 13, 2018 at 7:38

redochka

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answered Dec 21, 2012 at 16:56

JohnnyHK

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Comments

Joel Mata · Accepted Answer · 2017-08-24 12:10:47Z

5

Another version based on MongoTemplate:

public List<?> findLimitedSorted(Query query, Object target, String startFrom) {
    query.limit(100);
    query.with(new Sort(Sort.Direction.ASC, "<field_name>"));
    return getMongoTemplate().find(query, target.getClass());
}

answered Aug 24, 2017 at 12:10

Joel Mata

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1 Comment

themichaelscott Over a year ago

This is the correct answer. Always sort in your query, not after!

Aman Goel · Accepted Answer · 2017-06-20 10:21:33Z

0

Here is the solution which I found with filters, sorting and limit :

 List<Bson> queryFilters = new ArrayList<>();
    queryFilters.add(Filters.eq(SavedReportEntity.FIELD_USER_ID, userId));

   List<Document> documents = getMongoCollection().find(searchFilter).sort(sort).limit(10).into(new ArrayList<Document>());

you will get the list of Documents now you can play with it according to you.

answered Jun 20, 2017 at 10:21

Aman Goel

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Comments

Eric Aya · Accepted Answer · 2019-02-21 13:20:11Z

0

Getting DBObjects with sortting order from MongoDB:

List<DBObject> list = new LinkedList<DBObject>();    
    DBCursor cursor = db.getCollection("myCol").find().sort(new BasicDBObject("_id",-1)).limit(collection.find(query).count());
        while(cursur.hasNext){
        list.add(cursur.next());
    }
    if(!list.isEmpty())
        for(DBObject dbo: list){
            System.out.println(dbo);
        }
    else
        System.out.println("List is empty");

edited Feb 21, 2019 at 13:20

Eric Aya

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answered Feb 21, 2019 at 10:40

Vinayak Mahadev

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2 Comments

mooga Over a year ago

it would be nice if you add some explanation

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