simpledb

Class AbstractDbFileIterator

java.lang.Object

simpledb.AbstractDbFileIterator

All Implemented Interfaces:

DbFileIterator

public abstract class AbstractDbFileIterator
extends java.lang.Object
implements DbFileIterator

Helper for implementing DbFileIterators. Handles hasNext()/next() logic.

Field Summary

Fields

Modifier and Type	Field and Description
private Tuple	next

Constructor Summary

Constructors

Constructor and Description
AbstractDbFileIterator()

Method Summary

Modifier and Type	Method and Description
void	close() If subclasses override this, they should call super.close().
boolean	hasNext()
Tuple	next() Gets the next tuple from the operator (typically implementing by reading from a child operator or an access method).
protected abstract Tuple	readNext() Reads the next tuple from the underlying source.

Methods inherited from class java.lang.Object

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

Methods inherited from interface simpledb.DbFileIterator

open, rewind

Field Detail

next

private Tuple next

Constructor Detail

AbstractDbFileIterator

public AbstractDbFileIterator()

Method Detail

hasNext

public boolean hasNext()
                throws DbException,
                       TransactionAbortedException

Specified by:

hasNext in interface DbFileIterator

Returns:

true if there are more tuples available, false if no more tuples or iterator isn't open.

Throws:

DbException

TransactionAbortedException

next

public Tuple next()
           throws DbException,
                  TransactionAbortedException,
                  java.util.NoSuchElementException

Description copied from interface: DbFileIterator

Gets the next tuple from the operator (typically implementing by reading from a child operator or an access method).

Specified by:

next in interface DbFileIterator

Returns:

The next tuple in the iterator.

Throws:

java.util.NoSuchElementException - if there are no more tuples

DbException

TransactionAbortedException

close

public void close()

If subclasses override this, they should call super.close().

Specified by:

close in interface DbFileIterator

readNext

protected abstract Tuple readNext()
                           throws DbException,
                                  TransactionAbortedException

Reads the next tuple from the underlying source.

Returns:

the next Tuple in the iterator, null if the iteration is finished.

Throws:

DbException

TransactionAbortedException