org.modeshape.jcr.query.engine.process.JoinSequence 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 org.modeshape.common.annotation.NotThreadSafe;
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.RowExtractors.ExtractFromRow;
import org.modeshape.jcr.query.model.JoinType;
/**
* A {@link NodeSequence} implementation that performs a join of two delegate sequences.
*
* @see HashJoinSequence
* @author Randall Hauch ([email protected])
*/
@NotThreadSafe
public abstract class JoinSequence extends BufferingSequence {
public static final class Range {
private final K lower;
private final K upper;
private final boolean lowerIncluded;
private final boolean upperIncluded;
public Range( K lower,
boolean lowerIncluded,
K upper,
boolean upperIncluded ) {
this.lower = lower;
this.upper = upper;
this.lowerIncluded = lowerIncluded;
this.upperIncluded = upperIncluded;
}
/**
* Get the lower bound, if there is one.
*
* @return the lower bound, or null if there is none
*/
public K lowerBound() {
return lower;
}
/**
* Get the upper bound, if there is one.
*
* @return the upper bound, or null if there is none
*/
public K upperBound() {
return upper;
}
public boolean isUpperBoundIncluded() {
return upperIncluded;
}
public boolean isLowerBoundIncluded() {
return lowerIncluded;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(lowerIncluded ? '[' : '(');
sb.append(lower);
sb.append(',');
sb.append(upper);
sb.append(upperIncluded ? ']' : ')');
return sb.toString();
}
}
public static interface RangeProducer {
/**
* Determine the range of keys given the input key.
*
* @param input the input key
* @return the range of output keys; may be null if no range is valid
*/
Range getRange( K input );
}
protected final NodeSequence left;
protected final ExtractFromRow leftExtractor;
protected final int leftWidth;
protected final int totalWidth;
protected final JoinType joinType;
protected int batchSize = 100;
protected Batch currentLeft;
private BatchFactory batchFactory;
protected JoinSequence( String workspaceName,
NodeSequence left,
NodeSequence right,
ExtractFromRow leftExtractor,
ExtractFromRow rightExtractor,
JoinType joinType,
BufferManager bufferMgr,
CachedNodeSupplier nodeCache,
boolean pack,
boolean useHeap,
boolean allowDuplicates ) {
super(workspaceName, right, rightExtractor, bufferMgr, nodeCache, pack, useHeap, allowDuplicates);
this.left = left;
this.leftExtractor = leftExtractor;
this.leftWidth = left.width();
this.joinType = joinType;
this.totalWidth = left.width() + right.width();
}
@Override
public int width() {
return totalWidth;
}
@Override
public boolean isEmpty() {
if (left.isEmpty()) {
if (useNonMatchingRightRows() || useAllRightRowsWhenNoLeftRows()) {
// Even if the left is empty, we still need to use the right rows ...
return delegate.isEmpty();
}
// Left is empty, but we always have to have a left and don't care about the right ...
return true;
} else if (delegate.isEmpty()) {
if (useAllLeftRowsWhenNoMatchingRightRows()) {
// There are no right rows, but we still need to use all the rows on the left ...
assert !left.isEmpty();
return false;
}
}
return false;
}
@Override
public Batch nextBatch() {
// Find the next non-null and non-empty left batch ...
findNextNonEmptyLeftBatch();
if (batchFactory == null) {
// This is the first time through...
if (currentLeft == null) {
// And there are no rows on the left ...
if (useAllRightRowsWhenNoLeftRows()) {
// But we have to return all the right rows ...
batchFactory = new RightOnlyBatchFactory();
} else {
// We always return no rows, even if there are some on the right ...
batchFactory = new EmptyBatchFactory();
}
} else {
// Otherwise, initialize the batch factory ...
batchFactory = initialize();
}
}
// Now return a new Batch instance that performs the join ...
return batchFactory.nextBatch();
}
protected Batch findNextNonEmptyLeftBatch() {
while (currentLeft == null) {
currentLeft = left.nextBatch();
if (currentLeft == null) return null; // no more left
if (currentLeft.isEmpty() || !currentLeft.hasNext()) {
// Skip any empty batches ...
currentLeft = null;
}
}
return currentLeft;
}
/**
* Called once when the implementation is to create a {@link BatchFactory} for all batches returned by this join sequence.
* This is called only when we know that there are at least some rows on the left side.
*
* @return the batch factory that should be used to obtain the batches; never null
*/
protected abstract BatchFactory initialize();
/**
* Determine whether the algorithm that encounters no left rows should process the right rows. This method only returns true
* when the {@link #joinType join type} is a {@link JoinType#RIGHT_OUTER right outer join}.
*
* The {@link JoinType#CROSS cross join} (or Cartesian Product) is not included because the number of rows returned will be
* Nleft x Nright, where Nleft is the number of rows on the
* left-hand side, and Nright is the number of rows on the right-hand side. Therefore, if either is
* empty, the result is empty.
*
*
* @return true if the right rows should be returned when there are no left rows, or false otherwise
*/
protected boolean useAllRightRowsWhenNoLeftRows() {
return joinType == JoinType.RIGHT_OUTER;
}
/**
* Determine whether the algorithm that encounters a left row with no matching right rows should still include such left rows
* in the result. This method only returns true when the {@link #joinType join type} is a {@link JoinType#FULL_OUTER full
* outer join} or {@link JoinType#LEFT_OUTER left outer join}.
*
* @return true if the left rows should be returned even when there are no matching rows on the right, or false otherwise
*/
protected boolean useAllLeftRowsWhenNoMatchingRightRows() {
return joinType == JoinType.FULL_OUTER || joinType == JoinType.LEFT_OUTER;
}
/**
* Determine whether the algorithm should return rows from the right-side of the join that were no matched to left rows. This
* method only returns true when the {@link #joinType join type} is a {@link JoinType#FULL_OUTER full outer join} or
* {@link JoinType#RIGHT_OUTER right outer join}.
*
* @return true if the join algorithm should return rows on the right that did not match rows on the left, or false otherwise
*/
protected boolean useNonMatchingRightRows() {
return joinType == JoinType.FULL_OUTER || joinType == JoinType.RIGHT_OUTER;
}
@Override
public void close() {
try {
super.close();
} finally {
left.close();
}
}
/**
* A factory for batches.
*
* @author Randall Hauch ([email protected])
*/
protected static interface BatchFactory {
/**
* Get the next batch.
*
* @return the next batch, or null if there are no more batches
*/
Batch nextBatch();
}
/**
* A {@link BatchFactory} that always returns null.
*
* @author Randall Hauch ([email protected])
*/
protected final class EmptyBatchFactory implements BatchFactory {
@Override
public Batch nextBatch() {
return null;
}
}
/**
* A {@link BatchFactory} for batches that return only the right-hand rows. This is useful only when there are no left-hand
* rows and the join must still return all right-hand rows.
*
* @author Randall Hauch ([email protected])
*/
protected final class RightOnlyBatchFactory implements BatchFactory {
@Override
public Batch nextBatch() {
Batch right = delegate.nextBatch();
return right == null ? null : new RightOnlyBatch(right);
}
}
protected final class RightOnlyBatch implements Batch {
private final Batch right;
protected RightOnlyBatch( Batch right ) {
this.right = right;
}
@Override
public int width() {
return totalWidth;
}
@Override
public String getWorkspaceName() {
return workspaceName;
}
@Override
public boolean isEmpty() {
return right.isEmpty();
}
@Override
public long rowCount() {
return right.rowCount();
}
@Override
public boolean hasNext() {
return right.hasNext();
}
@Override
public void nextRow() {
right.nextRow();
}
@Override
public CachedNode getNode() {
// the left will always have at least one node, and we never have a left row ...
return null;
}
@Override
public CachedNode getNode( int index ) {
if (index < leftWidth) return null;
return right.getNode(index - leftWidth);
}
@Override
public float getScore() {
// the left will always have at least one score, and we never have a left row ...
return 0.0f;
}
@Override
public float getScore( int index ) {
if (index < leftWidth) return 0.0f;
return right.getScore(index - leftWidth);
}
}
/**
* A {@link BatchFactory} for batches that return only the left-hand rows. This is useful only when there are no right-hand
* rows and the join must still return all left-hand rows.
*
* @author Randall Hauch ([email protected])
*/
protected final class LeftOnlyBatchFactory implements BatchFactory {
@Override
public Batch nextBatch() {
Batch leftBatch = findNextNonEmptyLeftBatch();
if (leftBatch == null) return null;
currentLeft = null; // reset
return new LeftOnlyBatch(leftBatch);
}
}
protected final class LeftOnlyBatch implements Batch {
private final Batch left;
protected LeftOnlyBatch( Batch left ) {
this.left = left;
}
@Override
public int width() {
return totalWidth;
}
@Override
public String getWorkspaceName() {
return workspaceName;
}
@Override
public boolean isEmpty() {
return left.isEmpty();
}
@Override
public long rowCount() {
return left.rowCount();
}
@Override
public boolean hasNext() {
return left.hasNext();
}
@Override
public void nextRow() {
left.nextRow();
}
@Override
public CachedNode getNode() {
return left.getNode();
}
@Override
public CachedNode getNode( int index ) {
if (index < leftWidth) return left.getNode(index);
return null;
}
@Override
public float getScore() {
return left.getScore();
}
@Override
public float getScore( int index ) {
if (index < leftWidth) return left.getScore(index);
return 0.0f;
}
}
}
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