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

Using the ApacheImpalaDataAdapter

Use the adapter's Fill method to retrieve data from the data source. An empty DataTable instance is passed as an argument to the Fill method. When the method returns, the DataTable instance is populated with the queried data. Note that the ApacheImpalaDataAdapter is slower than the ApacheImpalaDataReader because the Fill method needs to retrieve all data from the data source before returning.

The following example selects the City and CompanyName columns of the Customers table:

C#

string connectionString = "Server=127.0.0.1;Port=21050;";

using (ApacheImpalaConnection connection = new ApacheImpalaConnection(connectionString)) {
  ApacheImpalaDataAdapter dataAdapter = new ApacheImpalaDataAdapter(
  "SELECT City, CompanyName FROM [CData].[Default].Customers", connection);

  DataTable table = new DataTable();
  dataAdapter.Fill(table);

  Console.WriteLine("Contents of Customers.");

  foreach (DataRow row in table.Rows) {
    Console.WriteLine("{0}: {1}", row["City"], row["CompanyName"]);
  }
}

VB.NET

Dim connectionString As String = "Server=127.0.0.1;Port=21050;"

Using connection As New ApacheImpalaConnection(connectionString)
  Dim dataAdapter As New ApacheImpalaDataAdapter("SELECT City, CompanyName FROM [CData].[Default].Customers", connection)

  Dim table As New DataTable()
  dataAdapter.Fill(table)

  Console.WriteLine("Contents of Customers.")

  For Each row As DataRow In table.Rows
    Console.WriteLine("{0}: {1}", row("City"), row("CompanyName"))
  Next
End Using