org.apache.lucene.search.spans.FieldMaskingSpanQuery Maven / Gradle / Ivy
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* 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.
*/
package org.apache.lucene.search.spans;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import java.io.IOException;
import java.util.Objects;
/**
* Wrapper to allow {@link SpanQuery} objects participate in composite
* single-field SpanQueries by 'lying' about their search field. That is,
* the masked SpanQuery will function as normal,
* but {@link SpanQuery#getField()} simply hands back the value supplied
* in this class's constructor.
*
* This can be used to support Queries like {@link SpanNearQuery} or
* {@link SpanOrQuery} across different fields, which is not ordinarily
* permitted.
*
* This can be useful for denormalized relational data: for example, when
* indexing a document with conceptually many 'children':
*
*
* teacherid: 1
* studentfirstname: james
* studentsurname: jones
*
* teacherid: 2
* studenfirstname: james
* studentsurname: smith
* studentfirstname: sally
* studentsurname: jones
*
*
* a SpanNearQuery with a slop of 0 can be applied across two
* {@link SpanTermQuery} objects as follows:
*
* SpanQuery q1 = new SpanTermQuery(new Term("studentfirstname", "james"));
* SpanQuery q2 = new SpanTermQuery(new Term("studentsurname", "jones"));
* SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
* Query q = new SpanNearQuery(new SpanQuery[]{q1, q2m}, -1, false);
*
* to search for 'studentfirstname:james studentsurname:jones' and find
* teacherid 1 without matching teacherid 2 (which has a 'james' in position 0
* and 'jones' in position 1).
*
* Note: as {@link #getField()} returns the masked field, scoring will be
* done using the Similarity and collection statistics of the field name supplied,
* but with the term statistics of the real field. This may lead to exceptions,
* poor performance, and unexpected scoring behaviour.
*/
public final class FieldMaskingSpanQuery extends SpanQuery {
private final SpanQuery maskedQuery;
private final String field;
public FieldMaskingSpanQuery(SpanQuery maskedQuery, String maskedField) {
this.maskedQuery = Objects.requireNonNull(maskedQuery);
this.field = Objects.requireNonNull(maskedField);
}
@Override
public String getField() {
return field;
}
public SpanQuery getMaskedQuery() {
return maskedQuery;
}
// :NOTE: getBoost and setBoost are not proxied to the maskedQuery
// ...this is done to be more consistent with things like SpanFirstQuery
@Override
public SpanWeight createWeight(IndexSearcher searcher, boolean needsScores, float boost) throws IOException {
return maskedQuery.createWeight(searcher, needsScores, boost);
}
@Override
public Query rewrite(IndexReader reader) throws IOException {
SpanQuery rewritten = (SpanQuery) maskedQuery.rewrite(reader);
if (rewritten != maskedQuery) {
return new FieldMaskingSpanQuery(rewritten, field);
}
return super.rewrite(reader);
}
@Override
public String toString(String field) {
StringBuilder buffer = new StringBuilder();
buffer.append("mask(");
buffer.append(maskedQuery.toString(field));
buffer.append(")");
buffer.append(" as ");
buffer.append(this.field);
return buffer.toString();
}
@Override
public boolean equals(Object other) {
return sameClassAs(other) &&
equalsTo(getClass().cast(other));
}
private boolean equalsTo(FieldMaskingSpanQuery other) {
return getField().equals(other.getField()) &&
getMaskedQuery().equals(other.getMaskedQuery());
}
@Override
public int hashCode() {
return classHash() ^
getMaskedQuery().hashCode() ^
getField().hashCode();
}
}