/*
* Copyright 2004-2005 The Apache Software Foundation or its licensors,
* as applicable.
*
* 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.apache.jackrabbit.core.query.lucene;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.search.FilteredTermEnum;
import org.apache.lucene.search.MultiTermQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.Weight;
import org.apache.lucene.search.Searcher;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.Similarity;
import org.apache.log4j.Logger;
import org.apache.commons.collections.map.LRUMap;
import java.io.IOException;
import java.util.BitSet;
import java.util.WeakHashMap;
import java.util.Map;
/**
* Implements a wildcard query on a lucene field with an embedded property name
* and a pattern.
* <p/>
* Wildcards are:
* <ul>
* <li><code>%</code> : matches zero or more characters</li>
* <li><code>_</code> : matches exactly one character</li>
* </ul>
*/
public class WildcardQuery extends Query {
/**
* Logger instance for this class.
*/
private static final Logger log = Logger.getLogger(WildcardQuery.class);
/**
* Name of the field to search.
*/
private final String field;
/**
* Name of the property to search.
*/
private final String propName;
/**
* The wildcard pattern.
*/
private final String pattern;
/**
* Simple result cache for previously calculated hits.
* key=IndexReader value=Map{key=String:pattern,value=BitSet:hits}
*/
private static final Map cache = new WeakHashMap();
/**
* Creates a new <code>WildcardQuery</code>.
*
* @param field the name of the field to search.
* @param propName name of the property to search.
* @param pattern the wildcard pattern.
*/
public WildcardQuery(String field, String propName, String pattern) {
this.field = field.intern();
this.propName = propName;
this.pattern = pattern;
}
/**
* Either rewrites this query to a lucene MultiTermQuery or in case of
* a TooManyClauses exception to a custom jackrabbit query implementation
* that uses a BitSet to collect all hits.
*
* @param reader the index reader to use for the search.
* @return the rewritten query.
* @throws IOException if an error occurs while reading from the index.
*/
public Query rewrite(IndexReader reader) throws IOException {
Query stdWildcardQuery = new MultiTermQuery(new Term(FieldNames.PROPERTIES, pattern)) {
protected FilteredTermEnum getEnum(IndexReader reader) throws IOException {
return new WildcardTermEnum(reader, field, propName, pattern);
}
};
try {
return stdWildcardQuery.rewrite(reader);
} catch (BooleanQuery.TooManyClauses e) {
// MultiTermQuery not possible
log.debug("Too many terms to enumerate, using custom WildcardQuery.");
return this;
}
}
/**
* Creates the <code>Weight</code> for this query.
*
* @param searcher the searcher to use for the <code>Weight</code>.
* @return the <code>Weigth</code> for this query.
*/
protected Weight createWeight(Searcher searcher) {
return new WildcardQueryWeight(searcher);
}
/**
* Returns a string representation of this query.
*
* @param field the field name for which to create a string representation.
* @return a string representation of this query.
*/
public String toString(String field) {
return propName + ":" + pattern;
}
/**
* The <code>Weight</code> implementation for this <code>WildcardQuery</code>.
*/
private class WildcardQueryWeight implements Weight {
/**
* The searcher in use
*/
private final Searcher searcher;
/**
* Creates a new <code>WildcardQueryWeight</code> instance using
* <code>searcher</code>.
*
* @param searcher a <code>Searcher</code> instance.
*/
public WildcardQueryWeight(Searcher searcher) {
this.searcher = searcher;
}
/**
* Returns this <code>WildcardQuery</code>.
*
* @return this <code>WildcardQuery</code>.
*/
public Query getQuery() {
return WildcardQuery.this;
}
/**
* {@inheritDoc}
*/
public float getValue() {
return 1.0f;
}
/**
* {@inheritDoc}
*/
public float sumOfSquaredWeights() throws IOException {
return 1.0f;
}
/**
* {@inheritDoc}
*/
public void normalize(float norm) {
}
/**
* Creates a scorer for this <code>WildcardQuery</code>.
*
* @param reader a reader for accessing the index.
* @return a <code>WildcardQueryScorer</code>.
* @throws IOException if an error occurs while reading from the index.
*/
public Scorer scorer(IndexReader reader) throws IOException {
return new WildcardQueryScorer(searcher.getSimilarity(), reader);
}
/**
* {@inheritDoc}
*/
public Explanation explain(IndexReader reader, int doc) throws IOException {
return new Explanation();
}
}
/**
* Implements a <code>Scorer</code> for this <code>WildcardQuery</code>.
*/
private final class WildcardQueryScorer extends Scorer {
/**
* The index reader to use for calculating the matching documents.
*/
private final IndexReader reader;
/**
* The documents ids that match this wildcard query.
*/
private final BitSet hits;
/**
* Set to <code>true</code> when the hits have been calculated.
*/
private boolean hitsCalculated = false;
/**
* The next document id to return
*/
private int nextDoc = -1;
/**
* The cache key to use to store the results.
*/
private final String cacheKey;
/**
* The map to store the results.
*/
private final Map resultMap;
/**
* Creates a new WildcardQueryScorer.
*
* @param similarity the similarity implementation.
* @param reader the index reader to use.
*/
WildcardQueryScorer(Similarity similarity, IndexReader reader) {
super(similarity);
this.reader = reader;
this.cacheKey = field + '\uFFFF' + propName + '\uFFFF' + pattern;
// check cache
synchronized (cache) {
Map m = (Map) cache.get(reader);
if (m == null) {
m = new LRUMap(10);
cache.put(reader, m);
}
resultMap = m;
}
synchronized (resultMap) {
BitSet result = (BitSet) resultMap.get(cacheKey);
if (result == null) {
result = new BitSet(reader.maxDoc());
} else {
hitsCalculated = true;
}
hits = result;
}
}
/**
* {@inheritDoc}
*/
public boolean next() throws IOException {
calculateHits();
nextDoc = hits.nextSetBit(nextDoc + 1);
return nextDoc > -1;
}
/**
* {@inheritDoc}
*/
public int doc() {
return nextDoc;
}
/**
* {@inheritDoc}
*/
public float score() {
return 1.0f;
}
/**
* {@inheritDoc}
*/
public boolean skipTo(int target) {
nextDoc = hits.nextSetBit(target);
return nextDoc > -1;
}
/**
* Returns an empty Explanation object.
* @return an empty Explanation object.
*/
public Explanation explain(int doc) {
return new Explanation();
}
/**
* Calculates the ids of the documents matching this wildcard query.
* @throws IOException if an error occurs while reading from the index.
*/
private void calculateHits() throws IOException {
if (hitsCalculated) {
return;
}
TermEnum terms = new WildcardTermEnum(reader, field, propName, pattern);
try {
// use unpositioned TermDocs
TermDocs docs = reader.termDocs();
try {
while (terms.term() != null) {
docs.seek(terms);
while (docs.next()) {
hits.set(docs.doc());
}
if (!terms.next()) {
break;
}
}
} finally {
docs.close();
}
} finally {
terms.close();
}
hitsCalculated = true;
// put to cache
synchronized (resultMap) {
resultMap.put(cacheKey, hits);
}
}
}
}