--- /dev/null
+package org.apache.lucene.search.spans;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+import java.lang.reflect.Method;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.search.MultiTermQuery;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TopTermsRewrite;
+import org.apache.lucene.search.ScoringRewrite;
+import org.apache.lucene.search.BooleanClause.Occur; // javadocs only
+
+/**
+ * Wraps any {@link MultiTermQuery} as a {@link SpanQuery},
+ * so it can be nested within other SpanQuery classes.
+ * <p>
+ * The query is rewritten by default to a {@link SpanOrQuery} containing
+ * the expanded terms, but this can be customized.
+ * <p>
+ * Example:
+ * <blockquote><pre>
+ * {@code
+ * WildcardQuery wildcard = new WildcardQuery(new Term("field", "bro?n"));
+ * SpanQuery spanWildcard = new SpanMultiTermQueryWrapper<WildcardQuery>(wildcard);
+ * // do something with spanWildcard, such as use it in a SpanFirstQuery
+ * }
+ * </pre></blockquote>
+ */
+public class SpanMultiTermQueryWrapper<Q extends MultiTermQuery> extends SpanQuery {
+ protected final Q query;
+ private Method getFieldMethod = null, getTermMethod = null;
+
+ /**
+ * Create a new SpanMultiTermQueryWrapper.
+ *
+ * @param query Query to wrap.
+ * <p>
+ * NOTE: This will call {@link MultiTermQuery#setRewriteMethod(MultiTermQuery.RewriteMethod)}
+ * on the wrapped <code>query</code>, changing its rewrite method to a suitable one for spans.
+ * Be sure to not change the rewrite method on the wrapped query afterwards! Doing so will
+ * throw {@link UnsupportedOperationException} on rewriting this query!
+ * In Lucene 3.x, MultiTermQuery allows queries to rewrite to different field names, but SpanQuery
+ * needs a fixed field. The wrapped query must therefore support getField() or getTerm().
+ * @throws IllegalArgumentException if the wrapped query does not provide getField() or getTerm().
+ */
+ public SpanMultiTermQueryWrapper(Q query) {
+ this.query = query;
+
+ MultiTermQuery.RewriteMethod method = query.getRewriteMethod();
+ if (method instanceof TopTermsRewrite) {
+ final int pqsize = ((TopTermsRewrite) method).getSize();
+ setRewriteMethod(new TopTermsSpanBooleanQueryRewrite(pqsize));
+ } else {
+ setRewriteMethod(SCORING_SPAN_QUERY_REWRITE);
+ }
+
+ // In Lucene 3.x, MTQ has no fixed field, we need to get it by reflection.
+ // If the underlying query does not allow to get a constant field, we throw IAE:
+ try {
+ getFieldMethod = query.getClass().getMethod("getField");
+ } catch (Exception e1) {
+ try {
+ getTermMethod = query.getClass().getMethod("getTerm");
+ } catch (Exception e2) {
+ try {
+ getTermMethod = query.getClass().getMethod("getPrefix");
+ } catch (Exception e3) {
+ throw new IllegalArgumentException("SpanMultiTermQueryWrapper can only wrap MultiTermQueries"+
+ " that can return a field name using getField() or getTerm()");
+ }
+ }
+ }
+ }
+
+ /**
+ * Expert: returns the rewriteMethod
+ */
+ public final SpanRewriteMethod getRewriteMethod() {
+ final MultiTermQuery.RewriteMethod m = query.getRewriteMethod();
+ if (!(m instanceof SpanRewriteMethod))
+ throw new UnsupportedOperationException("You can only use SpanMultiTermQueryWrapper with a suitable SpanRewriteMethod.");
+ return (SpanRewriteMethod) m;
+ }
+
+ /**
+ * Expert: sets the rewrite method. This only makes sense
+ * to be a span rewrite method.
+ */
+ public final void setRewriteMethod(SpanRewriteMethod rewriteMethod) {
+ query.setRewriteMethod(rewriteMethod);
+ }
+
+ @Override
+ public Spans getSpans(IndexReader reader) throws IOException {
+ throw new UnsupportedOperationException("Query should have been rewritten");
+ }
+
+ @Override
+ public String getField() {
+ try {
+ if (getFieldMethod != null) {
+ return (String) getFieldMethod.invoke(query);
+ } else {
+ assert getTermMethod != null;
+ return ((Term) getTermMethod.invoke(query)).field();
+ }
+ } catch (Exception e) {
+ throw new RuntimeException("Cannot invoke getField() or getTerm() on wrapped query.", e);
+ }
+ }
+
+ @Override
+ public String toString(String field) {
+ StringBuilder builder = new StringBuilder();
+ builder.append("SpanMultiTermQueryWrapper(");
+ builder.append(query.toString(field));
+ builder.append(")");
+ return builder.toString();
+ }
+
+ @Override
+ public Query rewrite(IndexReader reader) throws IOException {
+ final Query q = query.rewrite(reader);
+ if (!(q instanceof SpanQuery))
+ throw new UnsupportedOperationException("You can only use SpanMultiTermQueryWrapper with a suitable SpanRewriteMethod.");
+ return q;
+ }
+
+ @Override
+ public int hashCode() {
+ return 31 * query.hashCode();
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) return true;
+ if (obj == null) return false;
+ if (getClass() != obj.getClass()) return false;
+ final SpanMultiTermQueryWrapper other = (SpanMultiTermQueryWrapper) obj;
+ return query.equals(other.query);
+ }
+
+ /** Abstract class that defines how the query is rewritten. */
+ public static abstract class SpanRewriteMethod extends MultiTermQuery.RewriteMethod {
+ @Override
+ public abstract SpanQuery rewrite(IndexReader reader, MultiTermQuery query) throws IOException;
+ }
+
+ /**
+ * A rewrite method that first translates each term into a SpanTermQuery in a
+ * {@link Occur#SHOULD} clause in a BooleanQuery, and keeps the
+ * scores as computed by the query.
+ *
+ * @see #setRewriteMethod
+ */
+ public final static SpanRewriteMethod SCORING_SPAN_QUERY_REWRITE = new SpanRewriteMethod() {
+ private final ScoringRewrite<SpanOrQuery> delegate = new ScoringRewrite<SpanOrQuery>() {
+ @Override
+ protected SpanOrQuery getTopLevelQuery() {
+ return new SpanOrQuery();
+ }
+
+ @Override
+ protected void addClause(SpanOrQuery topLevel, Term term, float boost) {
+ final SpanTermQuery q = new SpanTermQuery(term);
+ q.setBoost(boost);
+ topLevel.addClause(q);
+ }
+ };
+
+ @Override
+ public SpanQuery rewrite(IndexReader reader, MultiTermQuery query) throws IOException {
+ return delegate.rewrite(reader, query);
+ }
+
+ // Make sure we are still a singleton even after deserializing
+ protected Object readResolve() {
+ return SCORING_SPAN_QUERY_REWRITE;
+ }
+ };
+
+ /**
+ * A rewrite method that first translates each term into a SpanTermQuery in a
+ * {@link Occur#SHOULD} clause in a BooleanQuery, and keeps the
+ * scores as computed by the query.
+ *
+ * <p>
+ * This rewrite method only uses the top scoring terms so it will not overflow
+ * the boolean max clause count.
+ *
+ * @see #setRewriteMethod
+ */
+ public static final class TopTermsSpanBooleanQueryRewrite extends SpanRewriteMethod {
+ private final TopTermsRewrite<SpanOrQuery> delegate;
+
+ /**
+ * Create a TopTermsSpanBooleanQueryRewrite for
+ * at most <code>size</code> terms.
+ */
+ public TopTermsSpanBooleanQueryRewrite(int size) {
+ delegate = new TopTermsRewrite<SpanOrQuery>(size) {
+ @Override
+ protected int getMaxSize() {
+ return Integer.MAX_VALUE;
+ }
+
+ @Override
+ protected SpanOrQuery getTopLevelQuery() {
+ return new SpanOrQuery();
+ }
+
+ @Override
+ protected void addClause(SpanOrQuery topLevel, Term term, float boost) {
+ final SpanTermQuery q = new SpanTermQuery(term);
+ q.setBoost(boost);
+ topLevel.addClause(q);
+ }
+ };
+ }
+
+ /** return the maximum priority queue size */
+ public int getSize() {
+ return delegate.getSize();
+ }
+
+ @Override
+ public SpanQuery rewrite(IndexReader reader, MultiTermQuery query) throws IOException {
+ return delegate.rewrite(reader, query);
+ }
+
+ @Override
+ public int hashCode() {
+ return 31 * delegate.hashCode();
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) return true;
+ if (obj == null) return false;
+ if (getClass() != obj.getClass()) return false;
+ final TopTermsSpanBooleanQueryRewrite other = (TopTermsSpanBooleanQueryRewrite) obj;
+ return delegate.equals(other.delegate);
+ }
+
+ }
+
+}
fnp / pylucene.git / blobdiff