Check if mongodb database exists?

Question

Is there a possibility to check if a mongo database allready exists?

Answer 1

I'd like to add a C# version. I'm using the MongoDB.Driver 2.2.2.

static bool DatabaseExists(string connectionString)
{
    var mongoUri = new MongoUrl(connectionString);
    var client = new MongoClient(mongoUri);

    var dbList = Enumerate(client.ListDatabases()).Select(db => db.GetValue("name").AsString);
    return dbList.Contains(mongoUri.DatabaseName);
}

static IEnumerable<BsonDocument> Enumerate(IAsyncCursor<BsonDocument> docs)
{
    while (docs.MoveNext())
    {
        foreach (var item in docs.Current)
        {
            yield return item;
        }
    }
}

Answer 2

Try this, it worked for me (on Mac OSx)

MongoClient mongoClient = new MongoClient("localhost");
/** **/
boolean dbExist =
    mongoClient.listDatabaseNames().
    into(new ArrayList<String>()).contains("TEST");

System.out.print(dbExist);

Answer 3

For anyone who comes here because the method getDatabaseNames(); is depreciated / not available, here is the new way to get the list of existing databases:

MongoClient mongoClient = new MongoClient();
MongoCursor<String> dbsCursor = mongoClient.listDatabaseNames().iterator();
while(dbsCursor.hasNext()) {
    System.out.println(dbsCursor.next());
}

Here is a method that validates if the database is found:

public Boolean databaseFound(String databaseName){
    MongoClient mongoClient = new MongoClient(); //Maybe replace it with an already existing client
    MongoCursor<String> dbsCursor = mongoClient.listDatabaseNames().iterator();
    while(dbsCursor.hasNext()) {
        if(dbsCursor.next().equals(databaseName))
            return true;
    }
    return false;
}

Answer 4

From the shell, if you want to explicitely check that a DB exists:

db.getMongo().getDBNames().indexOf("mydb");

Will return '-1' if "mydb" does not exist.

To use this from the shell:

if [ $(mongo localhost:27017 --eval 'db.getMongo().getDBNames().indexOf("mydb")' --quiet) -lt 0 ]; then
    echo "mydb does not exist"
else
    echo "mydb exists"
fi

Answer 5

in python using Pymongo

from pymongo import MongoClient

db_name = "foo"
conn = MongoClient('mongodb://localhost,localhost:27017')
db = self.conn[str(db_name)]
if bool(db_name in conn.database_names()):
   collection.drop()

Answer 6

In my case, I could not use listDatabaseNames, because my user did not have the rights to call this function. Instead, I just assume that it exists and call a method on this database, which will fail if it does not exist or if rights are missing.

Demo C# code:

/// <summary>
/// Tests the connection to the MongoDB server, and if the database already exists.
/// If not or an error is detected, an exception is thrown.
/// </summary>
public static void TestConnection(string mongoUrl, string mongoDatabase) {
   var client = new MongoClient(mongoUrl);
   var database = client.GetDatabase(mongoDatabase);
   try {
      // Try to perform an action on this database; will fail if it does not exist
      database.ListCollections(); 
   }
   catch {
      throw new Exception("Connection established, " +
         "but database does not exist (or missing rights): " + mongoDatabase);
   }    
}