ca.uqac.dim.turtledb

Class NAryRelation

java.lang.Object

ca.uqac.dim.turtledb.Relation

ca.uqac.dim.turtledb.NAryRelation

Direct Known Subclasses:

Intersection, Product, Union

public abstract class NAryRelation
extends Relation

An n-ary relation is an operator ☆ that accepts a variable number of operands n, with n ≥ 2, i.e. R₁☆R₂☆…☆R_n. Examples of n-ary relations are Union and Intersection. Note that an n-ary relation must be associative (hence the Join is not an n-ary relation).

Author:

sylvain

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	NAryRelation.NAryRelationCacheIterator
protected class	NAryRelation.NAryRelationStreamIterator

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.List<Relation>	m_relations The list of relations the operator acts on

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

m_streamingMode

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	NAryRelation()

Method Summary

Modifier and Type	Method and Description
protected void	acceptNAry(QueryVisitor v)
void	addOperand(Relation r)
int	getArity() Returns the arity of the operator, i.e.
Schema	getSchema() Returns the relation's schema
int	tupleCount() Returns the number of actual tuples present in the query.

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

accept, cacheIterator, contains, getCardinality, getDegree, isFragment, isLeaf, iterator, setStreamingMode, streamIterator, toString

Methods inherited from class java.lang.Object

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

Field Detail

m_relations

protected java.util.List<Relation> m_relations

The list of relations the operator acts on

Constructor Detail

NAryRelation

protected NAryRelation()

Method Detail

getSchema

public Schema getSchema()

Description copied from class: Relation

Returns the relation's schema

Specified by:

getSchema in class Relation

Returns:

The schema

addOperand

public void addOperand(Relation r)

getArity

public int getArity()

Returns the arity of the operator, i.e. the number of operands.

Returns:

The arity

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.

Specified by:

tupleCount in class Relation

Returns:

The tuple count

acceptNAry

protected void acceptNAry(QueryVisitor v)
                   throws QueryVisitor.VisitorException

Throws:

QueryVisitor.VisitorException