/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.jackrabbit.core.query.lucene.join;
import static javax.jcr.query.qom.QueryObjectModelConstants.JCR_JOIN_TYPE_LEFT_OUTER;
import static javax.jcr.query.qom.QueryObjectModelConstants.JCR_JOIN_TYPE_INNER;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.jcr.RepositoryException;
import javax.jcr.UnsupportedRepositoryOperationException;
import javax.jcr.query.QueryResult;
import javax.jcr.query.Row;
import javax.jcr.query.RowIterator;
import javax.jcr.query.qom.ChildNodeJoinCondition;
import javax.jcr.query.qom.Constraint;
import javax.jcr.query.qom.DescendantNodeJoinCondition;
import javax.jcr.query.qom.EquiJoinCondition;
import javax.jcr.query.qom.Join;
import javax.jcr.query.qom.JoinCondition;
import javax.jcr.query.qom.PropertyValue;
import javax.jcr.query.qom.QueryObjectModelFactory;
import javax.jcr.query.qom.SameNodeJoinCondition;
import javax.jcr.query.qom.Selector;
import javax.jcr.query.qom.Source;
import org.apache.jackrabbit.commons.iterator.RowIterable;
import org.apache.jackrabbit.commons.iterator.RowIteratorAdapter;
/**
* A join merger is used by the {@link QueryEngine} class to efficiently
* merge together two parts of a join query.
* <p>
* Each join condition type ({@link EquiJoinCondition equi-} and
* {@link SameNodeJoinCondition same}, {@link ChildNodeJoinCondition child}
* or {@link DescendantJoinCondition descendant} node joins) has it's own
* merger class that extends the functionality of this abstract base class
* with functionality specific to that join condition.
*/
abstract class JoinMerger {
/**
* Static factory method for creating a merger for the given join.
*
* @param join join
* @param columns columns of the query
* @param evaluator operand evaluator
* @param factory QOM factory
* @return join merger
* @throws RepositoryException if the merger can not be created
*/
public static JoinMerger getJoinMerger(
Join join, Map<String, PropertyValue> columns,
OperandEvaluator evaluator, QueryObjectModelFactory factory)
throws RepositoryException {
JoinCondition condition = join.getJoinCondition();
if (condition instanceof EquiJoinCondition) {
return new EquiJoinMerger(
join, columns, evaluator, factory,
(EquiJoinCondition) condition);
} else if (condition instanceof SameNodeJoinCondition) {
return new SameNodeJoinMerger(
join, columns, evaluator, factory,
(SameNodeJoinCondition) condition);
} else if (condition instanceof ChildNodeJoinCondition) {
return new ChildNodeJoinMerger(
join, columns, evaluator, factory,
(ChildNodeJoinCondition) condition);
} else if (condition instanceof DescendantNodeJoinCondition) {
return new DescendantNodeJoinMerger(
join, columns, evaluator, factory,
(DescendantNodeJoinCondition) condition);
} else {
throw new UnsupportedRepositoryOperationException(
"Unsupported join condition type: " + condition);
}
}
private final String type;
protected final Set<String> leftSelectors;
protected final Set<String> rightSelectors;
private final String[] selectorNames;
private final Map<String, PropertyValue> columns;
private final String[] columnNames;
protected final OperandEvaluator evaluator;
protected final QueryObjectModelFactory factory;
protected JoinMerger(
Join join, Map<String, PropertyValue> columns,
OperandEvaluator evaluator, QueryObjectModelFactory factory)
throws RepositoryException {
this.type = join.getJoinType();
this.leftSelectors = getSelectorNames(join.getLeft());
this.rightSelectors = getSelectorNames(join.getRight());
Set<String> selectors = new LinkedHashSet<String>();
selectors.addAll(leftSelectors);
selectors.addAll(rightSelectors);
this.selectorNames =
selectors.toArray(new String[selectors.size()]);
this.columns = columns;
this.columnNames =
columns.keySet().toArray(new String[columns.size()]);
this.evaluator = evaluator;
this.factory = factory;
}
public Set<String> getLeftSelectors() {
return leftSelectors;
}
public Set<String> getRightSelectors() {
return rightSelectors;
}
private Set<String> getSelectorNames(Source source)
throws RepositoryException {
if (source instanceof Selector) {
Selector selector = (Selector) source;
return Collections.singleton(selector.getSelectorName());
} else if (source instanceof Join) {
Join join = (Join) source;
Set<String> set = new LinkedHashSet<String>();
set.addAll(getSelectorNames(join.getLeft()));
set.addAll(getSelectorNames(join.getRight()));
return set;
} else {
throw new UnsupportedRepositoryOperationException(
"Unknown source type: " + source);
}
}
/**
* Merges the left and right dataset of a join query. Take special
* precaution for outer joins, as extra checks are needed to distinguish
* 'null' nodes vs 'not to be included' nodes
*
*
* @param leftRows
* the left dataset of the join
* @param rightRows
* the right dataset of the join
* @param excludingOuterJoinRowsSet
* if not <code>null</code> must be taken into consideration when
* merging OUTER JOINs
* @param rowComparator
* a comparator implementation that has to handle the 'is row
* equal to' problem, in the case of outer joins with
* excludingOuterJoinRowsSet
* @return a QueryResult that has the final JOIN resultset
* @throws RepositoryException
*/
public QueryResult merge(RowIterator leftRows, RowIterator rightRows,
Set<Row> excludingOuterJoinRowsSet, Comparator<Row> rowComparator)
throws RepositoryException {
Map<String, List<Row>> map = buildRightRowValues(rightRows);
if (JCR_JOIN_TYPE_INNER.equals(type) && !map.isEmpty()) {
List<Row> rows = new ArrayList<Row>();
for (Row leftRow : new RowIterable(leftRows)) {
for (String value : getLeftValues(leftRow)) {
List<Row> matchingRows = map.get(value);
if (matchingRows != null) {
for (Row rightRow : matchingRows) {
rows.add(mergeRow(leftRow, rightRow));
}
}
}
}
return asQueryResult(new RowIteratorAdapter(rows));
}
if (JCR_JOIN_TYPE_LEFT_OUTER.equals(type)) {
// there are no RIGHT dataset values
if (map.isEmpty()) {
// if there are no WHERE conditions, just return everything
// else return an empty set
if (excludingOuterJoinRowsSet == null) {
return asQueryResult(new RowIteratorAdapter(leftRows) {
@Override
public Object next() {
return mergeRow((Row) super.next(), null);
}
});
}
return asQueryResult(new RowIteratorAdapter(
Collections.emptySet()));
}
List<Row> rows = new ArrayList<Row>();
for (Row leftRow : new RowIterable(leftRows)) {
for (String value : getLeftValues(leftRow)) {
List<Row> matchingRows = map.get(value);
if (matchingRows != null) {
for (Row rightRow : matchingRows) {
// I have possible WHERE clauses on the join that I
// need to look at for each rightRow
if (excludingOuterJoinRowsSet == null) {
rows.add(mergeRow(leftRow, rightRow));
} else {
boolean isIncluded = false;
// apparently
// 'excludingOuterJoinRowsSet.contains' fails to
// match rows
// TODO can 'rightRow.getNode()' break because
// of joins that are bigger than 2 way?
// how does this perform for 3 way joins ?
for (Row r : excludingOuterJoinRowsSet) {
if(rowComparator.compare(rightRow, r) == 0){
isIncluded = true;
break;
}
}
if (isIncluded) {
rows.add(mergeRow(leftRow, rightRow));
}
}
}
} else {
// No matches in an outer join -> add a null row, if
// there are no 'WHERE' conditions
if (excludingOuterJoinRowsSet == null) {
rows.add(mergeRow(leftRow, null));
}
}
}
}
return asQueryResult(new RowIteratorAdapter(rows));
}
return asQueryResult(new RowIteratorAdapter(Collections.emptySet()));
}
private QueryResult asQueryResult(RowIterator rowIterator) {
return new SimpleQueryResult(columnNames, selectorNames, rowIterator);
}
private Map<String, List<Row>> buildRightRowValues(RowIterator rightRows)
throws RepositoryException {
Map<String, List<Row>> map = new HashMap<String, List<Row>>();
for (Row row : new RowIterable(rightRows)) {
for (String value : getRightValues(row)) {
List<Row> rows = map.get(value);
if (rows == null) {
rows = new ArrayList<Row>();
map.put(value, rows);
}
rows.add(row);
}
}
return map;
}
/**
* Merges the given left and right rows to a single joined row.
*
* @param left left row, possibly <code>null</code> in a right outer join
* @param right right row, possibly <code>null</code> in a left outer join
* @return joined row
*/
private Row mergeRow(Row left, Row right) {
return new JoinRow(
columns, evaluator,
left, leftSelectors, right, rightSelectors);
}
public abstract Set<String> getLeftValues(Row row)
throws RepositoryException;
public abstract Set<String> getRightValues(Row row)
throws RepositoryException;
public abstract List<Constraint> getRightJoinConstraints(Collection<Row> leftRows)
throws RepositoryException;
}