--- /dev/null
+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.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Set;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+
+/**
+ * A query that generates the union of documents produced by its subqueries, and that scores each document with the maximum
+ * score for that document as produced by any subquery, plus a tie breaking increment for any additional matching subqueries.
+ * This is useful when searching for a word in multiple fields with different boost factors (so that the fields cannot be
+ * combined equivalently into a single search field). We want the primary score to be the one associated with the highest boost,
+ * not the sum of the field scores (as BooleanQuery would give).
+ * If the query is "albino elephant" this ensures that "albino" matching one field and "elephant" matching
+ * another gets a higher score than "albino" matching both fields.
+ * To get this result, use both BooleanQuery and DisjunctionMaxQuery: for each term a DisjunctionMaxQuery searches for it in
+ * each field, while the set of these DisjunctionMaxQuery's is combined into a BooleanQuery.
+ * The tie breaker capability allows results that include the same term in multiple fields to be judged better than results that
+ * include this term in only the best of those multiple fields, without confusing this with the better case of two different terms
+ * in the multiple fields.
+ */
+public class DisjunctionMaxQuery extends Query implements Iterable<Query> {
+
+ /* The subqueries */
+ private ArrayList<Query> disjuncts = new ArrayList<Query>();
+
+ /* Multiple of the non-max disjunct scores added into our final score. Non-zero values support tie-breaking. */
+ private float tieBreakerMultiplier = 0.0f;
+
+ /** Creates a new empty DisjunctionMaxQuery. Use add() to add the subqueries.
+ * @param tieBreakerMultiplier the score of each non-maximum disjunct for a document is multiplied by this weight
+ * and added into the final score. If non-zero, the value should be small, on the order of 0.1, which says that
+ * 10 occurrences of word in a lower-scored field that is also in a higher scored field is just as good as a unique
+ * word in the lower scored field (i.e., one that is not in any higher scored field.
+ */
+ public DisjunctionMaxQuery(float tieBreakerMultiplier) {
+ this.tieBreakerMultiplier = tieBreakerMultiplier;
+ }
+
+ /**
+ * Creates a new DisjunctionMaxQuery
+ * @param disjuncts a Collection<Query> of all the disjuncts to add
+ * @param tieBreakerMultiplier the weight to give to each matching non-maximum disjunct
+ */
+ public DisjunctionMaxQuery(Collection<Query> disjuncts, float tieBreakerMultiplier) {
+ this.tieBreakerMultiplier = tieBreakerMultiplier;
+ add(disjuncts);
+ }
+
+ /** Add a subquery to this disjunction
+ * @param query the disjunct added
+ */
+ public void add(Query query) {
+ disjuncts.add(query);
+ }
+
+ /** Add a collection of disjuncts to this disjunction
+ * via Iterable<Query>
+ */
+ public void add(Collection<Query> disjuncts) {
+ this.disjuncts.addAll(disjuncts);
+ }
+
+ /** An Iterator<Query> over the disjuncts */
+ public Iterator<Query> iterator() {
+ return disjuncts.iterator();
+ }
+
+ /**
+ * Expert: the Weight for DisjunctionMaxQuery, used to
+ * normalize, score and explain these queries.
+ *
+ * <p>NOTE: this API and implementation is subject to
+ * change suddenly in the next release.</p>
+ */
+ protected class DisjunctionMaxWeight extends Weight {
+ /** The Similarity implementation. */
+ protected Similarity similarity;
+
+ /** The Weights for our subqueries, in 1-1 correspondence with disjuncts */
+ protected ArrayList<Weight> weights = new ArrayList<Weight>(); // The Weight's for our subqueries, in 1-1 correspondence with disjuncts
+
+ /** Construct the Weight for this Query searched by searcher. Recursively construct subquery weights. */
+ public DisjunctionMaxWeight(Searcher searcher) throws IOException {
+ this.similarity = searcher.getSimilarity();
+ for (Query disjunctQuery : disjuncts) {
+ weights.add(disjunctQuery.createWeight(searcher));
+ }
+ }
+
+ /** Return our associated DisjunctionMaxQuery */
+ @Override
+ public Query getQuery() { return DisjunctionMaxQuery.this; }
+
+ /** Return our boost */
+ @Override
+ public float getValue() { return getBoost(); }
+
+ /** Compute the sub of squared weights of us applied to our subqueries. Used for normalization. */
+ @Override
+ public float sumOfSquaredWeights() throws IOException {
+ float max = 0.0f, sum = 0.0f;
+ for (Weight currentWeight : weights) {
+ float sub = currentWeight.sumOfSquaredWeights();
+ sum += sub;
+ max = Math.max(max, sub);
+
+ }
+ float boost = getBoost();
+ return (((sum - max) * tieBreakerMultiplier * tieBreakerMultiplier) + max) * boost * boost;
+ }
+
+ /** Apply the computed normalization factor to our subqueries */
+ @Override
+ public void normalize(float norm) {
+ norm *= getBoost(); // Incorporate our boost
+ for (Weight wt : weights) {
+ wt.normalize(norm);
+ }
+ }
+
+ /** Create the scorer used to score our associated DisjunctionMaxQuery */
+ @Override
+ public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder,
+ boolean topScorer) throws IOException {
+ Scorer[] scorers = new Scorer[weights.size()];
+ int idx = 0;
+ for (Weight w : weights) {
+ Scorer subScorer = w.scorer(reader, true, false);
+ if (subScorer != null && subScorer.nextDoc() != DocIdSetIterator.NO_MORE_DOCS) {
+ scorers[idx++] = subScorer;
+ }
+ }
+ if (idx == 0) return null; // all scorers did not have documents
+ DisjunctionMaxScorer result = new DisjunctionMaxScorer(this, tieBreakerMultiplier, similarity, scorers, idx);
+ return result;
+ }
+
+ /** Explain the score we computed for doc */
+ @Override
+ public Explanation explain(IndexReader reader, int doc) throws IOException {
+ if (disjuncts.size() == 1) return weights.get(0).explain(reader,doc);
+ ComplexExplanation result = new ComplexExplanation();
+ float max = 0.0f, sum = 0.0f;
+ result.setDescription(tieBreakerMultiplier == 0.0f ? "max of:" : "max plus " + tieBreakerMultiplier + " times others of:");
+ for (Weight wt : weights) {
+ Explanation e = wt.explain(reader, doc);
+ if (e.isMatch()) {
+ result.setMatch(Boolean.TRUE);
+ result.addDetail(e);
+ sum += e.getValue();
+ max = Math.max(max, e.getValue());
+ }
+ }
+ result.setValue(max + (sum - max) * tieBreakerMultiplier);
+ return result;
+ }
+
+ } // end of DisjunctionMaxWeight inner class
+
+ /** Create the Weight used to score us */
+ @Override
+ public Weight createWeight(Searcher searcher) throws IOException {
+ return new DisjunctionMaxWeight(searcher);
+ }
+
+ /** Optimize our representation and our subqueries representations
+ * @param reader the IndexReader we query
+ * @return an optimized copy of us (which may not be a copy if there is nothing to optimize) */
+ @Override
+ public Query rewrite(IndexReader reader) throws IOException {
+ int numDisjunctions = disjuncts.size();
+ if (numDisjunctions == 1) {
+ Query singleton = disjuncts.get(0);
+ Query result = singleton.rewrite(reader);
+ if (getBoost() != 1.0f) {
+ if (result == singleton) result = (Query)result.clone();
+ result.setBoost(getBoost() * result.getBoost());
+ }
+ return result;
+ }
+ DisjunctionMaxQuery clone = null;
+ for (int i = 0 ; i < numDisjunctions; i++) {
+ Query clause = disjuncts.get(i);
+ Query rewrite = clause.rewrite(reader);
+ if (rewrite != clause) {
+ if (clone == null) clone = (DisjunctionMaxQuery)this.clone();
+ clone.disjuncts.set(i, rewrite);
+ }
+ }
+ if (clone != null) return clone;
+ else return this;
+ }
+
+ /** Create a shallow copy of us -- used in rewriting if necessary
+ * @return a copy of us (but reuse, don't copy, our subqueries) */
+ @Override @SuppressWarnings("unchecked")
+ public Object clone() {
+ DisjunctionMaxQuery clone = (DisjunctionMaxQuery)super.clone();
+ clone.disjuncts = (ArrayList<Query>) this.disjuncts.clone();
+ return clone;
+ }
+
+ // inherit javadoc
+ @Override
+ public void extractTerms(Set<Term> terms) {
+ for (Query query : disjuncts) {
+ query.extractTerms(terms);
+ }
+ }
+
+ /** Prettyprint us.
+ * @param field the field to which we are applied
+ * @return a string that shows what we do, of the form "(disjunct1 | disjunct2 | ... | disjunctn)^boost"
+ */
+ @Override
+ public String toString(String field) {
+ StringBuilder buffer = new StringBuilder();
+ buffer.append("(");
+ int numDisjunctions = disjuncts.size();
+ for (int i = 0 ; i < numDisjunctions; i++) {
+ Query subquery = disjuncts.get(i);
+ if (subquery instanceof BooleanQuery) { // wrap sub-bools in parens
+ buffer.append("(");
+ buffer.append(subquery.toString(field));
+ buffer.append(")");
+ }
+ else buffer.append(subquery.toString(field));
+ if (i != numDisjunctions-1) buffer.append(" | ");
+ }
+ buffer.append(")");
+ if (tieBreakerMultiplier != 0.0f) {
+ buffer.append("~");
+ buffer.append(tieBreakerMultiplier);
+ }
+ if (getBoost() != 1.0) {
+ buffer.append("^");
+ buffer.append(getBoost());
+ }
+ return buffer.toString();
+ }
+
+ /** Return true iff we represent the same query as o
+ * @param o another object
+ * @return true iff o is a DisjunctionMaxQuery with the same boost and the same subqueries, in the same order, as us
+ */
+ @Override
+ public boolean equals(Object o) {
+ if (! (o instanceof DisjunctionMaxQuery) ) return false;
+ DisjunctionMaxQuery other = (DisjunctionMaxQuery)o;
+ return this.getBoost() == other.getBoost()
+ && this.tieBreakerMultiplier == other.tieBreakerMultiplier
+ && this.disjuncts.equals(other.disjuncts);
+ }
+
+ /** Compute a hash code for hashing us
+ * @return the hash code
+ */
+ @Override
+ public int hashCode() {
+ return Float.floatToIntBits(getBoost())
+ + Float.floatToIntBits(tieBreakerMultiplier)
+ + disjuncts.hashCode();
+ }
+
+}
fnp / pylucene.git / blobdiff