ca.uqac.dim.turtledb

Class Table

java.lang.Object

ca.uqac.dim.turtledb.Relation

ca.uqac.dim.turtledb.Table

public class Table
extends Relation

A Table is a list of tuples. Since the leaves of a relational query tree are always tables, it is the only Relation that actually holds data.

Internally, tables are implemented as a sorted linked list of tuples. Sorting is maintained at insertion of each tuple. Consquently, a tuple that is to be modified will be removed, changed, and re-inserted so that the global ordering of tuples is always respected.

Author:

sylvain

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	Table.TableCacheIterator
protected class	Table.TableStreamIterator

Field Summary

Fields

Modifier and Type	Field and Description
protected int	m_cursor
protected java.lang.String	m_name
protected Schema	m_schema
protected java.util.List<Tuple>	m_tuples

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

m_streamingMode

Constructor Summary

Constructors

Constructor and Description
Table(Relation r) Constructor by copy

Method Summary

Modifier and Type	Method and Description
void	accept(QueryVisitor v)
RelationIterator	cacheIterator() Returns an iterator over tuples of the relation
boolean	contains(Tuple tup) Determines if a relation contains a given tuple.
void	copy(Relation r) Copies the contents of a relation into the current relation.
int	getCardinality() Computes the cardinality of a relation.
java.lang.String	getName() Gives the table's name
Schema	getSchema() Returns the relation's schema
boolean	isLeaf() Determines if a given operator is at the leaf of the query tree.
void	put(Tuple t) Adds a new tuple to the table.
void	putAll(java.util.Collection<Tuple> tuples) Adds a collection of tuples to the table.
void	setName(java.lang.String name) Sets a name for the table.
protected void	setSchema(Schema sch) Sets the table's schema
RelationStreamIterator	streamIterator() Returns an iterator over tuples of the relation
int	tupleCount() Returns the number of actual tuples present in the query.
protected java.util.Iterator<Tuple>	tupleIterator()

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

getDegree, isFragment, iterator, setStreamingMode, toString

Methods inherited from class java.lang.Object

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

Field Detail

m_tuples

protected java.util.List<Tuple> m_tuples

m_schema

protected Schema m_schema

m_cursor

protected int m_cursor

m_name

protected java.lang.String m_name

Constructor Detail

Table

public Table(Relation r)

Constructor by copy

Parameters:

r -

Method Detail

setName

public void setName(java.lang.String name)

Sets a name for the table. It is preferred to create a table with a name directly through the constructor, as using this method implies changing the table's name into every attribute of every tuple a posteriori.

Parameters:

name - The table's name

getName

public java.lang.String getName()

Gives the table's name

Returns:

The table's name

setSchema

protected void setSchema(Schema sch)

Sets the table's schema

Parameters:

sch - The schema

getSchema

public Schema getSchema()

Description copied from class: Relation

Returns the relation's schema

Specified by:

getSchema in class Relation

Returns:

The schema

put

public void put(Tuple t)

Adds a new tuple to the table. It is assumed that the tuple's degree is equal to the schema's degree. An assertion fails otherwise (but no exception is raised). This also affixes the table's name to each attribute, except if the table's name is the empty string.

The method put also ensures that the tuple is inserted at the correct location to keep the linked list sorted.

Parameters:

t - The tuple to add

putAll

public void putAll(java.util.Collection<Tuple> tuples)

Adds a collection of tuples to the table. This is just the repeated application of put to every tuple in the collection.

Parameters:

tuples - The tuples to add

accept

public void accept(QueryVisitor v)
            throws QueryVisitor.VisitorException

Specified by:

accept in class Relation

Throws:

QueryVisitor.VisitorException

copy

public void copy(Relation r)

Copies the contents of a relation into the current relation. In particular, invoking copy with a query tree triggers the computation of that query and the storing of the resulting tuples into the current relation.

Parameters:

r - The relation to copy from

getCardinality

public int getCardinality()

Description copied from class: Relation

Computes the cardinality of a relation. Except for instances of Table (which actually contain concrete tuples), calling this method will trigger the evaluation of the query tree and the enumeration of all tuples. It should be used sparingly.

Overrides:

getCardinality in class Relation

Returns:

The number of tuples in the relation

contains

public boolean contains(Tuple tup)

Determines if a relation contains a given tuple. Contrarily to the generic implementation of contains, the method for instances of Table is efficient, as it simply calls the contains method of the underlying list of tuples. It does not present the side effects (reset of enumeration) that the generic method has.

Overrides:

contains in class Relation

Parameters:

tup - The tuple to look for

Returns:

True if the tuple is present, false otherwise

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

isLeaf

public final 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:

tupleIterator

protected java.util.Iterator<Tuple> tupleIterator()

cacheIterator

public RelationIterator cacheIterator()

Description copied from class: Relation

Returns an iterator over tuples of the relation

Specified by:

cacheIterator in class Relation

Returns: