package org.apache.lucene.search;
/**
* Copyright 2004 The Apache Software Foundation
*
* 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.
*/
import java.io.IOException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.Term;
/** Implements search over a set of <code>Searchables</code>.
*
* <p>Applications usually need only call the inherited {@link #search(Query)}
* or {@link #search(Query,Filter)} methods.
*/
public class MultiSearcher extends Searcher {
/**
* Document Frequency cache acting as a Dummy-Searcher.
* This class is no full-fledged Searcher, but only supports
* the methods necessary to initialize Weights.
*/
private static class CachedDfSource extends Searcher {
private Map dfMap; // Map from Terms to corresponding doc freqs
private int maxDoc; // document count
public CachedDfSource(Map dfMap, int maxDoc) {
this.dfMap = dfMap;
this.maxDoc = maxDoc;
}
public int docFreq(Term term) {
int df;
try {
df = ((Integer) dfMap.get(term)).intValue();
} catch (NullPointerException e) {
throw new IllegalArgumentException("df for term " + term.text()
+ " not available");
}
return df;
}
public int[] docFreqs(Term[] terms) {
int[] result = new int[terms.length];
for (int i = 0; i < terms.length; i++) {
result[i] = docFreq(terms[i]);
}
return result;
}
public int maxDoc() {
return maxDoc;
}
public Query rewrite(Query query) {
// this is a bit of a hack. We know that a query which
// creates a Weight based on this Dummy-Searcher is
// always already rewritten (see preparedWeight()).
// Therefore we just return the unmodified query here
return query;
}
public void close() {
throw new UnsupportedOperationException();
}
public Document doc(int i) {
throw new UnsupportedOperationException();
}
public Explanation explain(Weight weight,int doc) {
throw new UnsupportedOperationException();
}
public void search(Weight weight, Filter filter, HitCollector results) {
throw new UnsupportedOperationException();
}
public TopDocs search(Weight weight,Filter filter,int n) {
throw new UnsupportedOperationException();
}
public TopFieldDocs search(Weight weight,Filter filter,int n,Sort sort) {
throw new UnsupportedOperationException();
}
};
private Searchable[] searchables;
private int[] starts;
private int maxDoc = 0;
/** Creates a searcher which searches <i>searchables</i>. */
public MultiSearcher(Searchable[] searchables) throws IOException {
this.searchables = searchables;
starts = new int[searchables.length + 1]; // build starts array
for (int i = 0; i < searchables.length; i++) {
starts[i] = maxDoc;
maxDoc += searchables[i].maxDoc(); // compute maxDocs
}
starts[searchables.length] = maxDoc;
}
/** Return the array of {@link Searchable}s this searches. */
public Searchable[] getSearchables() {
return searchables;
}
protected int[] getStarts() {
return starts;
}
// inherit javadoc
public void close() throws IOException {
for (int i = 0; i < searchables.length; i++)
searchables[i].close();
}
public int docFreq(Term term) throws IOException {
int docFreq = 0;
for (int i = 0; i < searchables.length; i++)
docFreq += searchables[i].docFreq(term);
return docFreq;
}
// inherit javadoc
public Document doc(int n) throws IOException {
int i = subSearcher(n); // find searcher index
return searchables[i].doc(n - starts[i]); // dispatch to searcher
}
/** Call {@link #subSearcher} instead.
* @deprecated
*/
public int searcherIndex(int n) {
return subSearcher(n);
}
/** Returns index of the searcher for document <code>n</code> in the array
* used to construct this searcher. */
public int subSearcher(int n) { // find searcher for doc n:
// replace w/ call to Arrays.binarySearch in Java 1.2
int lo = 0; // search starts array
int hi = searchables.length - 1; // for first element less
// than n, return its index
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 { // found a match
while (mid+1 < searchables.length && starts[mid+1] == midValue) {
mid++; // scan to last match
}
return mid;
}
}
return hi;
}
/** Returns the document number of document <code>n</code> within its
* sub-index. */
public int subDoc(int n) {
return n - starts[subSearcher(n)];
}
public int maxDoc() throws IOException {
return maxDoc;
}
public TopDocs search(Weight weight, Filter filter, int nDocs)
throws IOException {
HitQueue hq = new HitQueue(nDocs);
int totalHits = 0;
for (int i = 0; i < searchables.length; i++) { // search each searcher
TopDocs docs = searchables[i].search(weight, filter, nDocs);
totalHits += docs.totalHits; // update totalHits
ScoreDoc[] scoreDocs = docs.scoreDocs;
for (int j = 0; j < scoreDocs.length; j++) { // merge scoreDocs into hq
ScoreDoc scoreDoc = scoreDocs[j];
scoreDoc.doc += starts[i]; // convert doc
if(!hq.insert(scoreDoc))
break; // no more scores > minScore
}
}
ScoreDoc[] scoreDocs = new ScoreDoc[hq.size()];
for (int i = hq.size()-1; i >= 0; i--) // put docs in array
scoreDocs[i] = (ScoreDoc)hq.pop();
float maxScore = (totalHits==0) ? Float.NEGATIVE_INFINITY : scoreDocs[0].score;
return new TopDocs(totalHits, scoreDocs, maxScore);
}
public TopFieldDocs search (Weight weight, Filter filter, int n, Sort sort)
throws IOException {
FieldDocSortedHitQueue hq = null;
int totalHits = 0;
float maxScore=Float.NEGATIVE_INFINITY;
for (int i = 0; i < searchables.length; i++) { // search each searcher
TopFieldDocs docs = searchables[i].search (weight, filter, n, sort);
if (hq == null) hq = new FieldDocSortedHitQueue (docs.fields, n);
totalHits += docs.totalHits; // update totalHits
maxScore = Math.max(maxScore, docs.getMaxScore());
ScoreDoc[] scoreDocs = docs.scoreDocs;
for (int j = 0; j < scoreDocs.length; j++) { // merge scoreDocs into hq
ScoreDoc scoreDoc = scoreDocs[j];
scoreDoc.doc += starts[i]; // convert doc
if (!hq.insert (scoreDoc))
break; // no more scores > minScore
}
}
ScoreDoc[] scoreDocs = new ScoreDoc[hq.size()];
for (int i = hq.size() - 1; i >= 0; i--) // put docs in array
scoreDocs[i] = (ScoreDoc) hq.pop();
return new TopFieldDocs (totalHits, scoreDocs, hq.getFields(), maxScore);
}
// inherit javadoc
public void search(Weight weight, Filter filter, final HitCollector results)
throws IOException {
for (int i = 0; i < searchables.length; i++) {
final int start = starts[i];
searchables[i].search(weight, filter, new HitCollector() {
public void collect(int doc, float score) {
results.collect(doc + start, score);
}
});
}
}
public Query rewrite(Query original) throws IOException {
Query[] queries = new Query[searchables.length];
for (int i = 0; i < searchables.length; i++) {
queries[i] = searchables[i].rewrite(original);
}
return queries[0].combine(queries);
}
public Explanation explain(Weight weight, int doc) throws IOException {
int i = subSearcher(doc); // find searcher index
return searchables[i].explain(weight,doc-starts[i]); // dispatch to searcher
}
/**
* Create weight in multiple index scenario.
*
* Distributed query processing is done in the following steps:
* 1. rewrite query
* 2. extract necessary terms
* 3. collect dfs for these terms from the Searchables
* 4. create query weight using aggregate dfs.
* 5. distribute that weight to Searchables
* 6. merge results
*
* Steps 1-4 are done here, 5+6 in the search() methods
*
* @return rewritten queries
*/
protected Weight createWeight(Query original) throws IOException {
// step 1
Query rewrittenQuery = rewrite(original);
// step 2
Set terms = new HashSet();
rewrittenQuery.extractTerms(terms);
// step3
Term[] allTermsArray = new Term[terms.size()];
terms.toArray(allTermsArray);
int[] aggregatedDfs = new int[terms.size()];
for (int i = 0; i < searchables.length; i++) {
int[] dfs = searchables[i].docFreqs(allTermsArray);
for(int j=0; j<aggregatedDfs.length; j++){
aggregatedDfs[j] += dfs[j];
}
}
HashMap dfMap = new HashMap();
for(int i=0; i<allTermsArray.length; i++) {
dfMap.put(allTermsArray[i], new Integer(aggregatedDfs[i]));
}
// step4
int numDocs = maxDoc();
CachedDfSource cacheSim = new CachedDfSource(dfMap, numDocs);
return rewrittenQuery.weight(cacheSim);
}
}
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