org.modeshape.jcr.query.engine.process.IntersectSequence Maven / Gradle / Ivy
/*
* ModeShape (http://www.modeshape.org)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.modeshape.jcr.query.engine.process;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.modeshape.jcr.cache.CachedNode;
import org.modeshape.jcr.cache.CachedNodeSupplier;
import org.modeshape.jcr.query.BufferManager;
import org.modeshape.jcr.query.NodeSequence;
import org.modeshape.jcr.query.model.TypeSystem;
/**
* A {@link AbstractNodeKeysSequence} implementation which performs an INTERSECT operation between 2 other sequences,
* keeping only instances which have the same unique value in both sequences.
*
* @author Horia Chiorean ([email protected])
*/
public class IntersectSequence extends AbstractNodeKeysSequence {
public IntersectSequence( String workspaceName,
NodeSequence leftSequence,
NodeSequence rightSequence,
TypeSystem types,
BufferManager bufferMgr,
CachedNodeSupplier nodeCache,
boolean pack,
boolean useHeap ) {
super(workspaceName, leftSequence, rightSequence, types, bufferMgr, nodeCache, pack, useHeap);
}
@Override
protected Batch batchWrapper( Batch leftBatch ) {
return new IntersectBatch(leftBatch);
}
/**
* A batch implementation which wraps the left batch, but return rows from the matching keys from the right. The reason
* is that there may be duplicate keys on the right which should really be returned in case of an INTERSECT ALL and
* simply looking & filtering the left batch is not enough.
*/
protected class IntersectBatch implements Batch {
private final Batch leftBatch;
private Iterator matchingRightRows;
private BufferedRows.BufferedRow currentRight;
protected IntersectBatch( Batch leftBatch ) {
this.leftBatch = leftBatch;
}
@Override
public int width() {
return totalWidth;
}
@Override
public String getWorkspaceName() {
return workspaceName;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public long rowCount() {
return -1; // don't really know how many ...
}
@Override
public boolean hasNext() {
if (matchingRightRows != null && matchingRightRows.hasNext()) {
return true;
}
while (leftBatch.hasNext()) {
leftBatch.nextRow();
Object keyInLeftRow = keyInLeftRow(leftBatch);
matchingRightRows = matchingRightRows(keyInLeftRow);
if (matchingRightRows != null) {
//we found keys on the right matching the current key from the left (there may be multiple keys with the same value)
break;
}
}
return matchingRightRows != null && matchingRightRows.hasNext();
}
@Override
public void nextRow() {
currentRight = matchingRightRows.next();
}
@Override
public CachedNode getNode() {
if (currentRight == null) {
throw new NoSuchElementException();
}
return currentRight.getNode();
}
@Override
public CachedNode getNode( int index ) {
if (currentRight == null) {
throw new NoSuchElementException();
}
return currentRight.getNode(index);
}
@Override
public float getScore() {
if (currentRight == null) {
throw new NoSuchElementException();
}
return currentRight.getScore();
}
@Override
public float getScore( int index ) {
if (currentRight == null) {
throw new NoSuchElementException();
}
return currentRight.getScore(index);
}
}
@Override
public String toString() {
return "(intersect width=" + width() + " left=" + leftSequence + ", right=" + delegate + ", on " + extractor + " )";
}
}
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