ca.uqac.dim.turtledb

Class VariableTable

java.lang.Object

ca.uqac.dim.turtledb.Relation

ca.uqac.dim.turtledb.UnaryRelation

ca.uqac.dim.turtledb.VariableTable

public class VariableTable
extends UnaryRelation

A VariableTable is a placeholder for an actual relation. It is used to denote fragments of a query tree that are to be received from or sent to another site.

Author:

sylvain

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	VariableTable.VariableTableCacheIterator
protected class	VariableTable.VariableTableStreamIterator

Nested classes/interfaces inherited from class ca.uqac.dim.turtledb.UnaryRelation

UnaryRelation.UnaryRelationCacheIterator, UnaryRelation.UnaryRelationStreamIterator

Field Summary

Fields

Modifier and Type	Field and Description
protected java.lang.String	m_name The fragment's name
protected java.lang.String	m_site The fragment's site

Fields inherited from class ca.uqac.dim.turtledb.UnaryRelation

m_relation

Fields inherited from class ca.uqac.dim.turtledb.Relation

m_streamingMode

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	VariableTable()
	VariableTable(java.lang.String name)
	VariableTable(java.lang.String name, java.lang.String site)

Method Summary

Modifier and Type	Method and Description
void	accept(QueryVisitor v)
RelationIterator	cacheIterator() Returns an iterator over tuples of the relation
boolean	equals(java.lang.Object o)
boolean	equals(VariableTable t)
java.lang.String	getName() Gives the table's name
Schema	getSchema() Returns the relation's schema
java.lang.String	getSite() Gets the fragment's site.
boolean	isFragment() Determines if the query tree is a fragment.
boolean	isLeaf() Determines if a given operator is at the leaf of the query tree.
void	setName(java.lang.String name) Set the table's name.
void	setSite(java.lang.String site) Sets the fragment's site.
RelationStreamIterator	streamIterator() Returns an iterator over tuples of the relation
java.lang.String	toString() Pretty-prints a relation to a string
int	tupleCount() Returns the number of actual tuples present in the query.

Methods inherited from class ca.uqac.dim.turtledb.UnaryRelation

setRelation

Methods inherited from class ca.uqac.dim.turtledb.Relation

contains, getCardinality, getDegree, iterator, setStreamingMode

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

m_name

protected java.lang.String m_name

The fragment's name

m_site

protected java.lang.String m_site

The fragment's site

Constructor Detail

VariableTable

protected VariableTable()

VariableTable

public VariableTable(java.lang.String name)

VariableTable

public VariableTable(java.lang.String name,
                     java.lang.String site)

Method Detail

setSite

public void setSite(java.lang.String site)

Sets the fragment's site.

Parameters:

site -

See Also:

getSite}

getSite

public java.lang.String getSite()

Gets the fragment's site. If the VariableTable is a leaf in a query tree, it is placeholder for data that will be received from this site. If the VariableTable is the root of the query tree, it indicates that the results of the computation are to be sent to this site.

getSchema

public Schema getSchema()

Description copied from class: Relation

Returns the relation's schema

Specified by:

getSchema in class Relation

Returns:

The schema

accept

public void accept(QueryVisitor v)
            throws QueryVisitor.VisitorException

Specified by:

accept in class Relation

Throws:

QueryVisitor.VisitorException

toString

public java.lang.String toString()

Description copied from class: Relation

Pretty-prints a relation to a string

Overrides:

toString in class Relation

setName

public void setName(java.lang.String name)

Set the table's name.

Parameters:

name - The table's name

getName

public java.lang.String getName()

Gives the table's name

Returns:

The table's name

tupleCount

public int tupleCount()

Description copied from class: Relation

Returns the number of actual tuples present in the query. This number is different from the cardinality of the query; it counts the number of tuples that are present in the leaves of the query tree.

Overrides:

tupleCount in class UnaryRelation

Returns:

The tuple count

isFragment

public final boolean isFragment()

Description copied from class: Relation

Determines if the query tree is a fragment. This is the case when the tree's root is a VariableTable.

Overrides:

isFragment in class Relation

Returns:

True if the query tree is a fragment, false otherwise

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

equals

public boolean equals(VariableTable t)

isLeaf

public boolean isLeaf()

Description copied from class: Relation

Determines if a given operator is at the leaf of the query tree. Only instances of Table and VariableTable may be leaves.

Overrides:

isLeaf in class Relation

Returns:

streamIterator

public RelationStreamIterator streamIterator()

Description copied from class: Relation

Returns an iterator over tuples of the relation

Specified by:

streamIterator in class Relation

Returns:

cacheIterator

public RelationIterator cacheIterator()

Description copied from class: Relation

Returns an iterator over tuples of the relation

Specified by:

cacheIterator in class Relation

Returns: