This is my java class that will connect to Mongo DB and fetch the Data .
public class Test
{
public static void main(String args[])
{
DBCursor cursor = null;
DBCollection coll = null;
BasicDBObject query = new BasicDBObject();
String symbol = args[0];
query.put("symbol", "" + symbol);
cursor = coll.find(query);
int count = coll.find(query).count();
}
}
My question is , is it possible to know how many queries are made to the Mongo DB through this program ??
What i want to know is that whether two calls are made to the Mongo DB with this below statements
cursor = coll.find(query);
int count = coll.find(query).count();
Is it possible to know if two calls are amde to the Mongo DB with the above ??
You can use the MongoDB profiling to see the queries that are executed against the server. See the MongoDB documentation for further information: http://docs.mongodb.org/manual/reference/method/db.setProfilingLevel/
In short words: Execute db.setProfilingLevel(2) in your shell and look into the system.profile collection on your server.
If that is the only program connecting to MongoDB you can turn on profiling: http://docs.mongodb.org/manual/tutorial/manage-the-database-profiler/
You would turn profiling upto its max level (2), however if this is just one application of many then there might be (as in PHP) a MongoLog class ( http://php.net/manual/en/class.mongolog.php ) you could use.
Related
I was trying to get all the documents from a collection in mongoDB , I am using spring.
MongoTemplate mongoOperation = SpringMongoConfig1.mongoTemplate()
Here in monngoOperation I did not find any method which returns all the docs from a collection .
can anyone help in this ?
If you want to find all the documents of JavaDocumentName(any collection name in java)
List<JavaDocumentName> listRes = mongoOperation.findAll(JavaDocumentName.class);
You can do like this:
//If you don't need connection's configures. i.e. your mongo is in you localhost at 127.0.0.1:27017
MongoClient cliente = new MongoClient(); //to connect into a mongo DB
MongoDatabase mongoDb = client.getDatabase("DBname"); //get database, where DBname is the name of your database
MongoCollection<Document> robosCollection = mongoDb.getCollection("collectionName"); //get the name of the collection that you want
MongoCursor<Document> cursor = robosCollection.find().cursor();//Mongo Cursor interface implementing the iterator protocol
cursor.forEachRemaining(System.out::println); //print all documents in Collection using method reference
I want to copy the contents from one collection to another.
in mongod this can be done:
db.tempMongoItem.find().forEach( function(x){db.mongoItem.insert(x)} )
Using Java Mongo Driver, I try:
DB db = mongoClient.getDB("mydb")
CommandResult result = db.command("db.tempMongoItem.find().forEach( function(x){db.mongoItem.insert(x)} )")
But I get:
result = [serverUsed:localhost:27017, ok:0.0, errmsg:no such cmd: db.tempMongoItem.find().forEach( function(x){db.mongoItem.insert(x)} ), code:59, bad cmd:[db.tempMongoItem.find().forEach( function(x){db.mongoItem.insert(x)} ):true]]
Any ideas?
You need to emulate the same thing JS is doing in Java, which means getting a cursor and iterating over it, inserting each document into new collection.
Something like this (coll is current, coll2 is new collection):
DBCursor cursor = coll.find();
try {
while(cursor.hasNext()) {
coll2.insert(cursor.next());
}
} finally {
cursor.close();
}
Both coll and coll2 are assumed to be DBCollection type.
Since it appears you are copying within the same DB, there is another way to do this if you are using 2.6 MongoDB using aggregation framework $out stage:
db.collection.aggregate({"$out":"newCollection"});
Note that this is limited to outputting into the same DB that original collection is in.
The following JAVA code will copy the collection from source to destination for a given database name (using mongodb-driver 3.0.4)
/** Clone a collection.
*
* #param fromCollectionName - The name of collection to be cloned
* #param toCollectionName - The name of the cloned collection
* #param dbName - The name of the database
*/
public void cloneCollection(String fromCollectionName, String toCollectionName, String dbName) throws MongoException {
MongoCollection toCol = this.getCollection(toCollectionName, dbName);
if (toCol != null) {
throw new MongoException("The destination collection already exists.");
}
List<Document> ops = new ArrayList<>();
ops.add(new Document("$out",toCollectionName));
MongoCollection sourceCollection = this.getCollection(fromCollectionName, dbName);
sourceCollection.aggregate(ops);
}
public MongoCollection getCollection(String collection, String dbName) {
MongoClient mongo = new MongoClient(new ServerAddress("localhost", Integer.parseInt(port)));
MongoDatabase database = mongo.getDatabase(dbName);
return curdb.getCollection(collection);
}
Please note that this will not copy over the indices that you have created in source collection. You will have to copy the indices seperately
Following up on Asya's response, you can use Java 8 Lambda functions to do:
collSource.find().forEach((Block<Document>) collTarget::insertOne);
I am trying to create a capped collection for logging using mongoTemplate. However my collection size is growing beyond the size I passed as arguments. Can anyone please help with this.
public synchronized MongoTemplate getTemplate() {
if (template == null) {
Mongo mongo = null;
mongo = new Mongo(addrs);
template = new MongoTemplate(mongo, this.dbName);
if(!template.collectionExists(HttpRequestEntity.class)){
CollectionOptions options = new CollectionOptions(4,4,true);
template.createCollection(HttpRequestEntity.class, options);
}
}
return template;
}
For saving I am calling save on this template instance
getTemplate().save(entity);
Got it working after I deleted the collection from mongo console. I guess it was use old meta data as template.collectionExists(HttpRequestEntity.class) was returning true.
I am using MongoDb for my c sharp project instead of mysql, now i want to use query like select * from student Where (name is null or name='XXX') and (sno is null or sno=10), how can i build this query in mongodb.
thanks,
#dinnu.
This should get you started:
var mongoServer = MongoDB.Driver.MongoServer.Create("mongodb://localhost?safe=true");
var mongoDatabase = mongoServer.GetDatabase("test");
var mongoCollection = mongoDatabase.GetCollection<TModel>("Test");
var cursor = mongoCollection.Find(Query.And(
Query.Or(
Query.EQ("Name", "xxx"),
Query.EQ("Name", null)),
Query.Or(
Query.EQ("sno", 10)),
Query.EQ("sno", null)));
Where TModel is the type of the class you want to deserialize from the db. Now you can use cursor to iterate the results of that query, for example:
var someModel = cursor.FirstOrDefault();
Take a look at Fluent Mongo (https://github.com/craiggwilson/fluent-mongo). It adds Linq on top of the official 10gen driver. Thus far I have found using it to be a good experience. It is available via the Nuget or the GitHub.
I need to iterate through all of the collections in my MongoDB database and get the time when each of the collections was created (I understand that I could get the timestamp of each object in the collection, but I would rather not go that route if a simpler/faster method exists).
This should give you an idea of what I'm trying to do:
MongoDatabase _database;
// code elided
var result = _database.GetAllCollectionNames().Select(collectionName =>
{
_database.GetCollection( collectionName ) //.{GetCreatedDate())
});
As far as I know, MongoDB doesn't keep track of collection creation dates. However, it's really easy to do this yourself. Add a simple method, something like this, and use it whenever you create a new collection:
public static void CreateCollectionWithMetadata(string collectionName)
{
var result = _db.CreateCollection(collectionName);
if (result.Ok)
{
var collectionMetadata = _db.GetCollection("collectionMetadata");
collectionMetadata.Insert(new { Id = collectionName, Created = DateTime.Now });
}
}
Then whenever you need the information just query the collectionMetadata collection. Or, if you want to use an extension method like in your example, do something like this:
public static DateTime GetCreatedDate(this MongoCollection collection)
{
var collectionMetadata = _db.GetCollection("collectionMetadata");
var metadata = collectionMetadata.FindOneById(collection.Name);
var created = metadata["Created"].AsDateTime;
return created;
}
The "creation date" is not part of the collection's metadata. A collection does not "know" when it was created. Some indexes have an ObjectId() which implies a timestamp, but this is not consistent and not reliable.
Therefore, I don't believe this can be done.
Like Mr. Gates VP say, there is no way using the metadata... but you can get the oldest document in the collection and get it from the _id.
Moreover, you can insert an "empty" document in the collection for that purpose without recurring to maintain another collection.
And it's very easy get the oldest document:
old = db.collection.find({}, {_id}).sort({_id: 1}).limit(1)
dat = old._id.getTimestamp()
By default, all collection has an index over _id field, making the find efficient.
(I using MongoDb 3.6)
Seems like it's some necroposting but anyway: I tried to find an answer and got it:
Checked it in Mongo shell, don't know how to use in C#:
// db.payload_metadata.find().limit(1)
ObjectId("60379be2bec7a3c17e6b662b").getTimestamp()
ISODate("2021-02-25T12:45:22Z")