The Lucene SpanMultiTermQueryWrapper.java source code
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> * {@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>
*/
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, 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() {
@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 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);
}
}
}
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