/// <summary>Extract a chunk of result from a completed Future</summary>
/// <param name="h">Handle to the completed Future</param>
/// <param name="more">Receives true if there are more result, or false if all results have been transmitted</param>
/// <param name="first">Receives the first key in the page, or default if page is empty</param>
/// <param name="last">Receives the last key in the page, or default if page is empty</param>
/// <returns>Array of key/value pairs, or an exception</returns>
private static KeyValuePair <Slice, Slice>[] GetKeyValueArrayResultKeysOnly(FutureHandle h, out bool more, out Slice first, out Slice last)
{
var err = FdbNative.FutureGetKeyValueArrayKeysOnly(h, out var result, out more);
Fdb.DieOnError(err);
//note: result can only be null if an error occured!
Contract.Ensures(result != null);
first = result.Length > 0 ? result[0].Key : default;
last = result.Length > 0 ? result[result.Length - 1].Key : default;
return(result);
}