Package edu.caltech.nanodb.plannodes

Class SelectNode

java.lang.Object

edu.caltech.nanodb.plannodes.PlanNode

edu.caltech.nanodb.plannodes.SelectNode

All Implemented Interfaces:

java.lang.Cloneable

Direct Known Subclasses:

FileScanNode, SimpleFilterNode

public abstract class SelectNode
extends PlanNode

PlanNode representing the WHERE clause in a SELECT operation. This is the relational algebra Select operator.

Field Summary

Fields

Modifier and Type	Field	Description
protected Tuple	currentTuple	The current tuple that the node is selecting.
private boolean	done	True if we have finished scanning or pulling tuples from children.
Expression	predicate	Predicate used for selection.

Fields inherited from class edu.caltech.nanodb.plannodes.PlanNode

cost, environment, leftChild, rightChild, schema, stats

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SelectNode(Expression predicate)	Constructs a SelectNode that scans a file for tuples.
protected	SelectNode(PlanNode leftChild, Expression predicate)

Method Summary

Modifier and Type	Method	Description
protected abstract void	advanceCurrentTuple()	Helper function that advances the current tuple reference in the node.
protected PlanNode	clone()	Creates a copy of this select node and its subtree.
Tuple	getNextTuple()	Gets the next tuple selected by the predicate.
void	initialize()	Do initialization for the select operation.
protected boolean	isTupleSelected(Tuple tuple)

Methods inherited from class edu.caltech.nanodb.plannodes.PlanNode

addParentEnvironmentToPlanTree, cleanUp, duplicate, equals, getCost, getEnvironment, getSchema, getStats, hashCode, markCurrentPosition, prepare, printNodeTree, printNodeTree, printNodeTree, printNodeTreeToString, printNodeTreeToString, requiresLeftMarking, requiresRightMarking, resetToLastMark, resultsOrderedBy, setEnvironment, supportsMarking, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

predicate

public Expression predicate

Predicate used for selection.

currentTuple

protected Tuple currentTuple

The current tuple that the node is selecting.

done

private boolean done

True if we have finished scanning or pulling tuples from children.

Constructor Detail

SelectNode

protected SelectNode(Expression predicate)

Constructs a SelectNode that scans a file for tuples.

Parameters:

predicate - the selection criterion

SelectNode

protected SelectNode(PlanNode leftChild,
                     Expression predicate)

Method Detail

clone

protected PlanNode clone()
                  throws java.lang.CloneNotSupportedException

Creates a copy of this select node and its subtree. This method is used by PlanNode.duplicate() to copy a plan tree.

Overrides:

clone in class PlanNode

Throws:

java.lang.CloneNotSupportedException

initialize

public void initialize()

Do initialization for the select operation. Resets state variables.

Overrides:

initialize in class PlanNode

getNextTuple

public Tuple getNextTuple()

Gets the next tuple selected by the predicate.

Specified by:

getNextTuple in class PlanNode

Returns:

the tuple to be passed up to the next node.

Throws:

java.lang.IllegalStateException - if this is a scanning node with no algorithm or a filtering node with no child, or if the leftChild threw an IllegalStateException.

advanceCurrentTuple

protected abstract void advanceCurrentTuple()

Helper function that advances the current tuple reference in the node.

isTupleSelected

protected boolean isTupleSelected(Tuple tuple)