org.objectweb.medor.eval.api
Interface NodeEvaluator

All Known Implementing Classes:

BinaryIteratifNodeEvaluator, TupleCollectionNodeEvaluator, UnaryIteratifNodeEvaluator

public interface NodeEvaluator

This interface defines the controller object for the evaluation of a given QueryNode within a QueryTree. It is created at evaluation time by the NodeEvaluatorFactory, on request from the QueryEvaluator. The QueryEvaluator controls the overall evaluation by activating/killing the NodeEvaluator instances.

Method Summary

TupleCollection	fetchData(ParameterOperand[] parameters) This method executes the query on the underlying node.
long	getCacheSize()
EvaluationMetaData	getEvaluationMetaData() Returns the evaluation meta data associated with this node evaluator.
QueryNode	getQueryNode() Returns the QueryNode to which the NodeEvaluator is attached.
boolean	linkChildren() Opens the links between the current NodeEvaluator and the NodeEvaluators of the children QueryTrees for pipelining operations.
void	setCacheSize(long cacheSize)
void	setPrefetchBuffer(PrefetchBuffer pb) Associates a PrefetchBuffer to be filled by the collection computed by this evaluator.
boolean	unlinkChildren() Closes the links between the current NodeEvaluator and the NodeEvaluators of the children QueryTrees for pipelining operations.

Method Detail

unlinkChildren

public boolean unlinkChildren()

Closes the links between the current NodeEvaluator and the NodeEvaluators of the children QueryTrees for pipelining operations. TODO complete comments

linkChildren

public boolean linkChildren()

Opens the links between the current NodeEvaluator and the NodeEvaluators of the children QueryTrees for pipelining operations. TODO complete comments

fetchData

public TupleCollection fetchData(ParameterOperand[] parameters)
                          throws MedorException

This method executes the query on the underlying node. It controls the evaluation locally for this node. It returns the TupleCollection containing the result of the execution.

Throws:

MedorException

setPrefetchBuffer

public void setPrefetchBuffer(PrefetchBuffer pb)
                       throws MedorException

Associates a PrefetchBuffer to be filled by the collection computed by this evaluator.

Parameters:

pb - The PrefetchBuffer to be filled.

Throws:

MedorException

getCacheSize

public long getCacheSize()

setCacheSize

public void setCacheSize(long cacheSize)

getEvaluationMetaData

public EvaluationMetaData getEvaluationMetaData()

Returns the evaluation meta data associated with this node evaluator.

Returns:

the associated EvaluationMetaData

getQueryNode

public QueryNode getQueryNode()

Returns the QueryNode to which the NodeEvaluator is attached.