net.sf.farrago.runtime
Interface FarragoTransform

All Known Implementing Classes:

FarragoGeneratedCodeExamples.ExampleGeneratedFarragoTransform, FarragoTransformImpl

public interface FarragoTransform

A piece of generated code must implement this interface if it is to be callable from a Fennel JavaTransformExecStream wrapper. See FarragoTransformDef, which manages the construction of a FarragoTransform during statement preparation, in FarragoPreparingStmt.

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/runtime/FarragoTransform.java#11 $

Author:

Julian Hyde, Stephan Zuercher

Nested Class Summary

static class

FarragoTransform.InputBinding InputBinding binds a JavaTransformExecStream input's streamId to the ordinal assigned to that input by the stream graph.

Method Summary

int	execute(ByteBuffer outputBuffer, long quantum) Does a quantum of work.
void	init(FarragoRuntimeContext connection, String farragoTransformStreamName, FarragoTransform.InputBinding[] inputBindings) Binds all inputs and initializes the transform.
void	restart() Restarts this transform's underlying TupleIter(s).
void	setInputFetchTimeout(long millisecs) Sets a timeout for fetching an input row.

Method Detail

init

void init(FarragoRuntimeContext connection,
          String farragoTransformStreamName,
          FarragoTransform.InputBinding[] inputBindings)

Binds all inputs and initializes the transform. This method is typically generated. It is called by FarragoExecutableJavaStmt.execute(net.sf.farrago.session.FarragoSessionRuntimeContext).

Parameters:

connection - the FarragoRuntimeContext of the query that contains this transform.

farragoTransformStreamName - the globally unique name of the ExecStream that implements this transform.

inputBindings - bindings between the transform's input streamIds and the ordinal assigned to them in the stream graph

execute

int execute(ByteBuffer outputBuffer,
            long quantum)

Does a quantum of work. Called by Fennel's JavaTransformExecStream.

Parameters:

outputBuffer - output ByteBuffer into which tuples are marshaled

quantum - the maximum number of tuples that should be processed before returning (in practice this is limited to 2^32)

Returns:

bytes marshalled into outputBuffer; 0 means end of stream, less than 0 indicates an input underflow

setInputFetchTimeout

void setInputFetchTimeout(long millisecs)

Sets a timeout for fetching an input row. 0 means poll, infinity (ie Long.MAX_VALUE) means block. The default is to block;

restart

void restart()

Restarts this transform's underlying TupleIter(s).