We Keep Coding

Copy (update if exists) document from one collection to another

I want to copy a document from one collection of mongodb to another collection (or update if exist) through java.
I don't want to append each field of existing collection and then insert to another. How can I do this?
Here are two collections, temp and national. temp has only one collection, which I have to copy to national or update if it exists.
MongoCursor<Document> cursor = db.getCollection("temp").find().iterator();
try {
Document doc = new Document(cursor.next());
Document new_doc = new Document("$set",doc);
doc.append("booking_id",cursor.next().get("booking_id"));
MongoCursor<Document> cursor1 = db.getCollection("national").find(doc).iterator();
Bson filter = Filters.eq("booking_id", args);
Bson update = Filters.elemMatch("booking_id", filter);
UpdateOptions options = new UpdateOptions().upsert(true);
national.updateOne(filter, new_doc, options);
}
finally {
cursor.close();
}

If you want replace Doc2 with Doc1 you can use replaceOne()
replaceOne() replaces the first matching document in the collection that matches the filter, using the replacement document.
https://docs.mongodb.com/v3.2/reference/method/db.collection.replaceOne/

Mongo DB Remove Duplcates in a field in a Collection Javadriver

I am trying to remove duplicates in a collection using java driver in mongodb.
I am using the code
table = db.getCollection("dummy_data_OLD");
BasicDBObject query = new BasicDBObject("url", 1)
.append("unique", true).append("dropDups", true);
table.createIndex(query);
It will create a unique index , but still duplicates present in the db.
Is there any problem in my code?

This creates an index on the fields url, unique and dropDups. When you want to create an index using options, you need to provide these as a second DBObject.
DBObject fields = new BasicDBObject("url", 1);
DBObject options = new BasicDBObject("unique", true).append("dropDups", true);
db.getCollection("dummy_data_OLD").createIndex(fields, options);

MongoDB Java pull

i tried to remove an embedded document without succcess.
I'm looking for the java way of following instruction:
db.games.update({'_id': 73}, {$pull: {'goals': {'goal': 4}}})

The Java documentation is pretty clear, you are just constructing BSON objects to match their respective JSON counterparts as used in the shell:
BasicDBObject query = new BasicDBObject("_id", 73);
BasicDBObject fields = new BasicDBObject("goals",
new BasicDBObject( "goal", 4));
BasicDBObject update = new BasicDBObject("$pull",fields);
games.update( query, update );

Using Bson is similar.
Bson query = new Document().append("_id", 73);
Bson fields = new Document().append("goals", new Document().append( "goal", 4));
Bson update = new Document("$pull",fields);
games.updateOne( query, update );

Apache Lucene - Creating and Storing an Index?

This post if a follow-on from my previous question:
Apache Lucene - Optimizing Searching
I want to create an index from title stored in my database, store the index on the server from which I am running my web application, and have that index available to all users who are using the search feature on the web application.
I will update the index when a new title is added, edited or deleted.
I cannot find a tutorial to do this in Apache Lucene, so can anyone help me code this in Java (using Spring).

From my understanding to your question, you need to do the following :
1) Index you data (titles in your case)
first you need to implement the code that create that index for you data, check this sample of code.
Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_CURRENT);
// Store the index in memory:
//Directory directory = new RAMDirectory();
Store an index on disk
Directory directory = FSDirectory.open(indexfilesDirPathOnYourServer);
IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_CURRENT, analyzer);
IndexWriter iwriter = new IndexWriter(directory, config);
Document doc = new Document();
String title = getTitle();
doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
iwriter.addDocument(doc);
iwriter.close();
here you need to loop over you all data.
2) Search for you indexed data.
you can search for you data by using this code:
DirectoryReader ireader = DirectoryReader.open(indexfilesDirPathOnYourServer);
IndexSearcher isearcher = new IndexSearcher(ireader);
// Parse a simple query that searches for "text":
QueryParser parser = new QueryParser(Version.LUCENE_CURRENT, "fieldname", analyzer);//note here we used the same analyzer object
Query query = parser.parse("test");//test is am example for a search query
ScoreDoc[] hits = isearcher.search(query, null, 1000).scoreDocs;
// Iterate through the results:
for (int i = 0; i < hits.length; i++) {
Document hitDoc = isearcher.doc(hits[i].doc);
System.out.println(hitDoc.get("fieldname"));
}
ireader.close();
directory.close();
Note : here you don't have to fetch all the data from your DB, you can directly get it from index. also you don't have to re-create the whole index each time user search or fetch the data, you can update the title from time to time when you add/update or delete one by one (the title that have been updated or deleted not the whole indexed titles).
to update index use :
Term keyTerm = new Term(KEY_FIELD, KEY_VALUE);
iwriter.updateDocument(keyTerm, updatedFields);
to delete index use :
Term keyTerm = new Term(KEY_FIELD, KEY_VALUE);
iwriter.deleteDocuments(keyTerm);
Hope that help you.

MongoDb's $set equivalent in its java Driver

Is there a way in which I can modify the value of one of the keys in MongoDb via its Java Driver. I tried out the following:
someCollection.update(DBObject query, DBObject update);
someCollection.findAndModify(DBObject query, DBObject update);
But both the functions completely replace the queried document with the updated document. What is the way to update only one of the value of a particular key as in the case of using $set in the mongo shell.(apart from making a completely new Document with all fields copied and one of the fields updated).

BasicDBObject carrier = new BasicDBObject();
BasicDBObject query = new BasicDBObject();
query.put("YOUR_QUERY_STRING", YOUR_QUERY_VALUE);
BasicDBObject set = new BasicDBObject("$set", carrier);
carrier.put("a", 6);
carrier.put("b", "wx1");
myColl.updateMany(query, set);
This should work, the answer which is accepted is not right above.

Try something like this:
BasicDBObject set = new BasicDBObject("$set", new BasicDBObject("age", 10));
set.append("$set", new BasicDBObject("name", "Some Name"));
someCollection.update(someSearchQuery, set);
Also look at this example.

None of the solutions mentioned above worked for me. I realized that the query should be a Document type and not a BasicDBObject :
Document set = new Document("$set", new Document("firstName","newValue"));
yourMongoCollection.updateOne(new Document("_id",objectId), set);
Where "yourMongoCollection" is of type "MongoCollection" and "objectId" of type "ObjectId"

The previous answer pointed me in the right direction, but the code to add a 2nd object to the update did not work for me. The following did:
BasicDBObject newValues = new BasicDBObject("age", 10);
newValues.append("name", "Some Name");
BasicDBObject set = new BasicDBObject("$set", newValues);
collection.update(someSearchQuery, set);

First, unless I want to reconfigure/reformat/"re-type" my values I'd go only with findAndModify and not update.
Here is a fully working example for c&p purposes... Enjoy:
Boolean updateValue(DB db, DBCollection collection, String id, String key, Object newValue)
{
DBCollection collection = db.getCollection(<collection name>);
// Identify your required document (id, key, etc...)
DBObject query = new BasicDBObject("_ID",<ID or key value>);
DBObject update = new BasicDBObject("$set", new BasicDBObject(key, newValue));
//These flags will guarantee that you'lls get the updated result
DBObject result = collection.findAndModify(query, null, null, false, update,true, true);
//Just for precaution....
if(result == null)
return false;
return result.get(key).equals(newValue);
}

According to the documents, $set is an alise for $addFields, so just use that:
var iterable = collection.aggregate(Arrays.asList(
Aggregates.addFields(new Field("foo", "bar"))
));