com.bigdata.btree.LeafTupleIterator Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Nov 15, 2006
*/
package com.bigdata.btree;
import java.util.NoSuchElementException;
/**
* Visits the values of a {@link Leaf} in the external key ordering. There is
* exactly one value per key for a leaf node.
*
* @author Bryan Thompson
* @version $Id$
*/
public class LeafTupleIterator implements ITupleIterator {
private final Leaf leaf;
private final AbstractTuple tuple;
private int index;
private int lastVisited = -1;
// private final byte[] fromKey;
//
// private final byte[] toKey;
// first index to visit.
private final int fromIndex;
// first index to NOT visit.
private final int toIndex;
private final boolean hasDeleteMarkers;
private final boolean visitDeleted;
public LeafTupleIterator(Leaf leaf) {
this(leaf, new Tuple(leaf.btree, IRangeQuery.DEFAULT), null, null);
}
public LeafTupleIterator(final Leaf leaf, final AbstractTuple tuple) {
this(leaf, tuple, null, null);
}
/**
*
* @param leaf
* The leaf whose entries will be traversed (required).
* @param tuple
* Used to hold the output values (required).
* @param fromKey
* The first key whose entry will be visited or null
* if the lower bound on the key traversal is not constrained.
* @param toKey
* The first key whose entry will NOT be visited or
* null if the upper bound on the key traversal is
* not constrained.
* @param flags
* Flags specifying whether the keys and/or values will be
* materialized.
*
* @exception IllegalArgumentException
* if fromKey is given and is greater than toKey.
*/
public LeafTupleIterator(final Leaf leaf, final AbstractTuple tuple,
final byte[] fromKey, final byte[] toKey) {
assert leaf != null;
assert tuple != null;
this.leaf = leaf;
this.tuple = tuple;
this.hasDeleteMarkers = leaf.hasDeleteMarkers();
this.visitDeleted = (tuple.flags() & IRangeQuery.DELETED) != 0;
// this.fromKey = fromKey; // may be null (no lower bound).
//
// this.toKey = toKey; // may be null (no upper bound).
{ // figure out the first index to visit.
int fromIndex;
if (fromKey != null) {
fromIndex = leaf.getKeys().search(fromKey);
if (fromIndex < 0) {
fromIndex = -fromIndex - 1;
}
} else {
fromIndex = 0;
}
this.fromIndex = fromIndex;
}
{ // figure out the first index to NOT visit.
int toIndex;
if (toKey != null) {
toIndex = leaf.getKeys().search(toKey);
if (toIndex < 0) {
toIndex = -toIndex - 1;
}
} else {
toIndex = leaf.getKeyCount();
}
this.toIndex = toIndex;
}
if (fromIndex > toIndex) {
throw new IllegalArgumentException("fromKey > toKey");
}
// starting index is the lower bound.
index = fromIndex;
}
/**
* Examines the entry at {@link #index}. If it passes the criteria for an
* entry to visit then return true. Otherwise increment the {@link #index}
* until either all entries in this leaf have been exhausted -or- the an
* entry is identified that passes the various criteria.
*/
public boolean hasNext() {
// if(filter == null) {
//
// return index >= fromIndex && index < toIndex;
//
// }
for( ; index >= fromIndex && index < toIndex; index++) {
/*
* Skip deleted entries unless specifically requested.
*/
if (hasDeleteMarkers && !visitDeleted
&& leaf.getDeleteMarker(index)) {
// skipping a deleted version.
continue;
}
// entry @ index is next to visit.
return true;
}
// nothing left to visit in this leaf.
return false;
}
public ITuple next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
lastVisited = index++;
tuple.copy(lastVisited, leaf);
return tuple;
}
/**
* This operation is not supported.
*
* Note: There are two ways in which you can achieve the semantics of
* {@link #remove()}. One is to use an {@link ITupleCursor}, which
* correctly handles traversal with concurrent modification. The other is to
* use a {@link AbstractChunkedTupleIterator}, which buffers the tuples
* first and then does a "delete" behind in order to avoid concurrent
* modification during traversal.
*
* @throws UnsupportedOperationException
* always.
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
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