simpledb

Class OrderBy

java.lang.Object

simpledb.Operator

simpledb.OrderBy

All Implemented Interfaces:

java.io.Serializable, DbIterator

public class OrderBy
extends Operator

OrderBy is an operator that implements a relational ORDER BY.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	asc
private DbIterator	child
private java.util.ArrayList<Tuple>	childTups
private java.util.Iterator<Tuple>	it
private int	orderByField
private java.lang.String	orderByFieldName
private static long	serialVersionUID
private TupleDesc	td

Constructor Summary

Constructors

Constructor and Description
OrderBy(int orderbyField, boolean asc, DbIterator child) Creates a new OrderBy node over the tuples from the iterator.

Method Summary

Modifier and Type	Method and Description
void	close() Closes this iterator.
protected Tuple	fetchNext() Operator.fetchNext implementation.
DbIterator[]	getChildren()
int	getOrderByField()
java.lang.String	getOrderFieldName()
TupleDesc	getTupleDesc() Returns the TupleDesc associated with this DbIterator.
boolean	isASC()
void	open() Opens the iterator.
void	rewind() Resets the iterator to the start.
void	setChildren(DbIterator[] children) Set the children(child) of this operator.

Methods inherited from class simpledb.Operator

getEstimatedCardinality, hasNext, next, setEstimatedCardinality

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

child

private DbIterator child

td

private TupleDesc td

childTups

private java.util.ArrayList<Tuple> childTups

orderByField

private int orderByField

orderByFieldName

private java.lang.String orderByFieldName

it

private java.util.Iterator<Tuple> it

asc

private boolean asc

Constructor Detail

OrderBy

public OrderBy(int orderbyField,
               boolean asc,
               DbIterator child)

Creates a new OrderBy node over the tuples from the iterator.

Parameters:

orderbyField - the field to which the sort is applied.

asc - true if the sort order is ascending.

child - the tuples to sort.

Method Detail

isASC

public boolean isASC()

getOrderByField

public int getOrderByField()

getOrderFieldName

public java.lang.String getOrderFieldName()

getTupleDesc

public TupleDesc getTupleDesc()

Description copied from interface: DbIterator

Returns the TupleDesc associated with this DbIterator.

Specified by:

getTupleDesc in interface DbIterator

Specified by:

getTupleDesc in class Operator

Returns:

return the TupleDesc of the output tuples of this operator

open

public void open()
          throws DbException,
                 java.util.NoSuchElementException,
                 TransactionAbortedException

Description copied from interface: DbIterator

Opens the iterator. This must be called before any of the other methods.

Specified by:

open in interface DbIterator

Overrides:

open in class Operator

Throws:

DbException - when there are problems opening/accessing the database.

java.util.NoSuchElementException

TransactionAbortedException

close

public void close()

Description copied from class: Operator

Closes this iterator. If overridden by a subclass, they should call super.close() in order for Operator's internal state to be consistent.

Specified by:

close in interface DbIterator

Overrides:

close in class Operator

rewind

public void rewind()
            throws DbException,
                   TransactionAbortedException

Description copied from interface: DbIterator

Resets the iterator to the start.

Throws:

DbException - when rewind is unsupported.

TransactionAbortedException

fetchNext

protected Tuple fetchNext()
                   throws java.util.NoSuchElementException,
                          TransactionAbortedException,
                          DbException

Operator.fetchNext implementation. Returns tuples from the child operator in order

Specified by:

fetchNext in class Operator

Returns:

The next tuple in the ordering, or null if there are no more tuples

Throws:

java.util.NoSuchElementException

TransactionAbortedException

DbException

getChildren

public DbIterator[] getChildren()

Specified by:

getChildren in class Operator

Returns:

return the children DbIterators of this operator. If there is only one child, return an array of only one element. For join operators, the order of the children is not important. But they should be consistent among multiple calls.

setChildren

public void setChildren(DbIterator[] children)

Description copied from class: Operator

Set the children(child) of this operator. If the operator has only one child, children[0] should be used. If the operator is a join, children[0] and children[1] should be used.

Specified by:

setChildren in class Operator

Parameters:

children - the DbIterators which are to be set as the children(child) of this operator