The CData ADO.NET Provider for Presto implements two ADO.NET interfaces you can use to retrieve data from Presto: PrestoDataAdapter and PrestoDataReader objects. Whereas PrestoDataAdapter objects retrieve a single result set of all the data that matches a query, PrestoDataReader objects fetch data in subset increments as needed.

Using the PrestoDataReader

The PrestoDataReader retrieves data faster than the PrestoDataAdapter because it can retrieve data in pages. As you read data from the PrestoDataReader, it periodically requests the next page of results from the data source, if required. This causes results to be returned at a faster rate. The following example selects all the columns from the [Hive].[Default].Customers table:

C#

string connectionString = "Server=127.0.0.1;Port=8080;";

using (PrestoConnection connection = new PrestoConnection(connectionString)) {
  PrestoCommand cmd = new PrestoCommand("SELECT * FROM [Hive].[Default].Customers", connection);
  
  PrestoDataReader rdr = cmd.ExecuteReader();

  while (rdr.Read()) {
    Console.WriteLine(String.Format("\t{0} --> \t\t{1}", rdr["Id"], rdr["Name"]));
  }
}

VB.NET

Dim connectionString As String = "Server=127.0.0.1;Port=8080;"

Using connection As New PrestoConnection(connectionString)
  Dim cmd As New PrestoCommand("SELECT * FROM [Hive].[Default].Customers", connection)

  Dim rdr As PrestoDataReader = cmd.ExecuteReader()

  While rdr.Read()
    Console.WriteLine([String].Format(vbTab & "{0} --> " & vbTab & vbTab & "{1}", rdr("Id"), rdr("Name")))
  End While
End Using