com.bigdata.btree.filter

Class Advancer<E>

java.lang.Object

cutthecrap.utils.striterators.FilterBase

com.bigdata.btree.filter.Advancer<E>

Type Parameters:

E - The type of the objects visited by the source iterator.

All Implemented Interfaces:

ITupleFilter<E>, IFilter, IPropertySet, Serializable, Cloneable

Direct Known Subclasses:

ContextAdvancer, DistinctMultiTermAdvancer, DistinctTermAdvancer, ZOrderIndexBigMinAdvancer

public abstract class Advancer<E>
extends FilterBase
implements ITupleFilter<E>

Used to write logic that advances an ITupleCursor to another key after it visits some element. For example, the "distinct term scan" for the RDF DB is written in this manner.

Author:

Bryan Thompson

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.apache.log4j.Logger	log
protected ITupleCursor<E>	src Set by #filter(ITupleCursor).

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Advancer()

Method Summary

Methods

Modifier and Type	Method and Description
protected abstract void	advance(ITuple<E> tuple) Offers an opportunity to advance the source ITupleCursor to a new key using {@link ITupleCursor#seek(byte[]).
ITupleIterator<E>	filterOnce(Iterator src, Object context) Wrap the source iterator with this filter.
protected boolean	init() Hook for one-time initialization invoked before the advancer visits the first tuple.

Methods inherited from class cutthecrap.utils.striterators.FilterBase

addFilter, filter, getProperty, getRequiredProperty, setProperty, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface cutthecrap.utils.striterators.IFilter

filter

Methods inherited from interface cutthecrap.utils.striterators.IPropertySet

getProperty

Field Detail

log

protected static final transient org.apache.log4j.Logger log

src

protected ITupleCursor<E> src

Set by #filter(ITupleCursor).

Constructor Detail

Advancer

protected Advancer()

Method Detail

filterOnce

public final ITupleIterator<E> filterOnce(Iterator src,
                           Object context)

Description copied from class: FilterBase

Wrap the source iterator with this filter.

Specified by:

filterOnce in interface ITupleFilter<E>

Specified by:

filterOnce in class FilterBase

Parameters:

src - The source iterator (MUST be an ITupleCursor).

context - The iterator evaluation context.

Returns:

init

protected boolean init()

Hook for one-time initialization invoked before the advancer visits the first tuple. The default implementation simply returns true.

Returns:

false if nothing should be visited.

advance

protected abstract void advance(ITuple<E> tuple)

Offers an opportunity to advance the source ITupleCursor to a new key using {@link ITupleCursor#seek(byte[]).

Parameters:

tuple - The current value.