/*
* 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;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.jackrabbit.core.query.lucene.SharedFieldCache.StringIndex;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.ScoreDocComparator;
import org.apache.lucene.search.SortComparator;
import org.apache.lucene.search.SortField;
/**
* Implements a <code>SortComparator</code> which knows how to sort on a lucene
* field that contains values for multiple properties.
* <p/>
* <b>Important:</b> The ScoreDocComparator returned by {@link #newComparator}
* does not implement the contract for {@link ScoreDocComparator#sortValue(ScoreDoc)}
* properly. The method will always return an empty String to save memory consumption
* on large property ranges. Those values are only of relevance when queries
* are executed with a <code>MultiSearcher</code>, which is currently not the
* case in Jackrabbit.
*/
public class SharedFieldSortComparator extends SortComparator {
/**
* A <code>SharedFieldSortComparator</code> that is based on
* {@link FieldNames#PROPERTIES}.
*/
static final SortComparator PROPERTIES = new SharedFieldSortComparator(FieldNames.PROPERTIES);
/**
* The name of the shared field in the lucene index.
*/
private final String field;
/**
* If <code>true</code> <code>ScoreDocComparator</code> will returns term
* values when {@link org.apache.lucene.search.ScoreDocComparator#sortValue(org.apache.lucene.search.ScoreDoc)}
* is called, otherwise only a dummy value is returned.
*/
private final boolean createComparatorValues;
/**
* Creates a new <code>SharedFieldSortComparator</code> for a given shared
* field.
*
* @param fieldname the shared field.
*/
public SharedFieldSortComparator(String fieldname) {
this(fieldname, false);
}
/**
* Creates a new <code>SharedFieldSortComparator</code> for a given shared
* field.
*
* @param fieldname the shared field.
* @param createComparatorValues if <code>true</code> creates values
* for the <code>ScoreDocComparator</code>s.
* @see #createComparatorValues
*/
public SharedFieldSortComparator(String fieldname, boolean createComparatorValues) {
this.field = fieldname;
this.createComparatorValues = createComparatorValues;
}
/**
* Creates a new <code>ScoreDocComparator</code> for an embedded
* <code>propertyName</code> and a <code>reader</code>.
* @param reader the index reader.
* @param propertyName the name of the property to sort.
* @return a <code>ScoreDocComparator</code> for the
* @throws IOException
* @throws IOException
*/
public ScoreDocComparator newComparator(final IndexReader reader, final String propertyName) throws IOException {
final List readers = new ArrayList();
getIndexReaders(readers, reader);
final SharedFieldCache.StringIndex[] indexes = new SharedFieldCache.StringIndex[readers.size()];
int maxDoc = 0;
final int[] starts = new int[readers.size() + 1];
for (int i = 0; i < readers.size(); i++) {
IndexReader r = (IndexReader) readers.get(i);
starts[i] = maxDoc;
maxDoc += r.maxDoc();
indexes[i] = SharedFieldCache.INSTANCE.getStringIndex(r, field,
FieldNames.createNamedValue(propertyName, ""),
SharedFieldSortComparator.this, createComparatorValues);
}
starts[readers.size()] = maxDoc;
return new ScoreDocComparator() {
public final int compare(final ScoreDoc i, final ScoreDoc j) {
int idx1 = readerIndex(i.doc);
int idx2 = readerIndex(j.doc);
String iTerm = indexes[idx1].getTerm(i.doc - starts[idx1]);
String jTerm = indexes[idx2].getTerm(j.doc - starts[idx2]);
if (iTerm == jTerm) {
return 0;
} else if (iTerm == null) {
return -1;
} else if (jTerm == null) {
return 1;
} else {
return iTerm.compareTo(jTerm);
}
}
/**
* Returns an empty if no lookup table is available otherwise the
* index term for the score doc <code>i</code>.
*
* @param i
* the score doc.
* @return the sort value if available.
*/
public Comparable sortValue(final ScoreDoc i) {
if (createComparatorValues) {
int idx = readerIndex(i.doc);
return indexes[idx].getTerm(i.doc - starts[idx]);
} else {
// return dummy value
return "";
}
}
public int sortType() {
return SortField.CUSTOM;
}
/**
* Returns the reader index for document <code>n</code>.
*
* @param n document number.
* @return the reader index.
*/
private int readerIndex(int n) {
int lo = 0;
int hi = readers.size() - 1;
while (hi >= lo) {
int mid = (lo + hi) >> 1;
int midValue = starts[mid];
if (n < midValue) {
hi = mid - 1;
} else if (n > midValue) {
lo = mid + 1;
} else {
while (mid + 1 < readers.size() && starts[mid + 1] == midValue) {
mid++;
}
return mid;
}
}
return hi;
}
};
}
/**
* @throws UnsupportedOperationException always.
*/
protected Comparable getComparable(String termtext) {
throw new UnsupportedOperationException();
}
/**
* Checks if <code>reader</code> is of type {@link MultiIndexReader} and if
* that's the case calls this method recursively for each reader within the
* multi index reader; otherwise the reader is simply added to the list.
*
* @param readers the list of index readers.
* @param reader the reader to check.
*/
private void getIndexReaders(List readers, IndexReader reader) {
if (reader instanceof MultiIndexReader) {
IndexReader[] r = ((MultiIndexReader) reader).getIndexReaders();
for (int i = 0; i < r.length; i++) {
getIndexReaders(readers, r[i]);
}
} else {
readers.add(reader);
}
}
}