/// <summary>
/// Maps each group of the current DataFrame using a UDF and
/// returns the result as a DataFrame.
///
/// The user-defined function should take an Apache Arrow RecordBatch
/// and return another Apache Arrow RecordBatch. For each group, all
/// columns are passed together as a RecordBatch to the user-function and
/// the returned RecordBatch are combined as a DataFrame.
///
/// The returned <see cref="RecordBatch"/> can be of arbitrary length and its
/// schema must match <paramref name="returnType"/>.
/// </summary>
/// <param name="returnType">
/// The <see cref="StructType"/> that represents the shape of the return data set.
/// </param>
/// <param name="func">A grouped map user-defined function.</param>
/// <returns>New DataFrame object with the UDF applied.</returns>
public DataFrame Apply(StructType returnType, Func <RecordBatch, RecordBatch> func)
{
ArrowGroupedMapWorkerFunction.ExecuteDelegate wrapper =
new ArrowGroupedMapUdfWrapper(func).Execute;
UserDefinedFunction udf = UserDefinedFunction.Create(
Reference.Jvm,
func.Method.ToString(),
CommandSerDe.Serialize(
wrapper,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row),
UdfUtils.PythonEvalType.SQL_GROUPED_MAP_PANDAS_UDF,
returnType.Json);
IReadOnlyList <string> columnNames = _dataFrame.Columns();
var columns = new Column[columnNames.Count];
for (int i = 0; i < columnNames.Count; ++i)
{
columns[i] = _dataFrame[columnNames[i]];
}
Column udfColumn = udf.Apply(columns);
return(new DataFrame((JvmObjectReference)Reference.Invoke(
"flatMapGroupsInPandas",
udfColumn.Expr())));
}
/// <summary>
/// Helper function to register wrapped udf.
/// </summary>
/// <param name="name">Name of the udf</param>
/// <param name="func">Wrapped UDF function</param>
/// <param name="evalType">The EvalType of the function</param>
/// <param name="returnType">The return type of the function in JSON format</param>
private void Register(string name, Delegate func, UdfUtils.PythonEvalType evalType, string returnType)
{
byte[] command = CommandSerDe.Serialize(
func,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row);
UserDefinedFunction udf = UserDefinedFunction.Create(
_jvmObject.Jvm,
name,
command,
evalType,
returnType);
_jvmObject.Invoke("registerPython", name, udf);
}
/// <summary>
/// Helper function to register wrapped udf.
/// </summary>
/// <typeparam name="TResult">Return type of the udf</typeparam>
/// <param name="name">Name of the udf</param>
/// <param name="func">Wrapped UDF function</param>
/// <param name="evalType">The EvalType of the function.</param>
internal void Register <TResult>(string name, Delegate func, UdfUtils.PythonEvalType evalType)
{
byte[] command = CommandSerDe.Serialize(
func,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row);
var udf = UserDefinedFunction.Create(
_jvmObject.Jvm,
name,
command,
evalType,
UdfUtils.GetReturnType(typeof(TResult)));
_jvmObject.Invoke("registerPython", name, udf);
}
public DataStreamWriter Foreach(IForeachWriter writer)
{
RDD.WorkerFunction.ExecuteDelegate wrapper =
new ForeachWriterWrapperUdfWrapper(
new ForeachWriterWrapper(writer).Process).Execute;
_jvmObject.Invoke(
"foreach",
_jvmObject.Jvm.CallConstructor(
"org.apache.spark.sql.execution.python.PythonForeachWriter",
UdfUtils.CreatePythonFunction(
_jvmObject.Jvm,
CommandSerDe.Serialize(
wrapper,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row)),
DataType.FromJson(_jvmObject.Jvm, _df.Schema().Json)));
return(this);
}
/// <summary>
/// Helper function to register wrapped udf.
/// </summary>
/// <typeparam name="TResult">Return type of the udf</typeparam>
/// <param name="name">Name of the udf</param>
/// <param name="func">Wrapped UDF function</param>
private void Register <TResult>(string name, Delegate func)
{
byte[] command = CommandSerDe.Serialize(
func,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row);
JvmObjectReference pythonFunction =
UdfUtils.CreatePythonFunction(_jvmObject.Jvm, command);
var udf = new UserDefinedFunction(
_jvmObject.Jvm.CallConstructor(
"org.apache.spark.sql.execution.python.UserDefinedPythonFunction",
name,
pythonFunction,
GetDataType <TResult>(),
(int)UdfUtils.GetPythonEvalType(),
true // udfDeterministic
));
_jvmObject.Invoke("registerPython", name, udf);
}
public void Write(Stream stream, Command[] commands)
{
SerDe.Write(stream, commands.Length);
foreach (Command command in commands)
{
SerDe.Write(stream, command.ArgOffsets.Length);
foreach (int argOffset in command.ArgOffsets)
{
SerDe.Write(stream, argOffset);
}
SerDe.Write(stream, command.ChainedUdfs.Length);
foreach (Delegate udf in command.ChainedUdfs)
{
byte[] serializedCommand = CommandSerDe.Serialize(
udf,
CommandSerDe.SerializedMode.Row,
CommandSerDe.SerializedMode.Row);
SerDe.Write(stream, serializedCommand.Length);
SerDe.Write(stream, serializedCommand);
}
}
}
