/*
 * 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.queries.function.valuesource;

import java.io.IOException;
import java.util.Map;

import org.apache.lucene.index.BinaryDocValues;
import org.apache.lucene.index.DocValues;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.MultiTerms;
import org.apache.lucene.index.ReaderUtil;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.docvalues.IntDocValues;
import org.apache.lucene.util.BytesRef;

Use a field value and find the Document Frequency within another field.
Since:solr 4.0
/** * Use a field value and find the Document Frequency within another field. * * @since solr 4.0 */
public class JoinDocFreqValueSource extends FieldCacheSource { public static final String NAME = "joindf"; protected final String qfield; public JoinDocFreqValueSource(String field, String qfield) { super(field); this.qfield = qfield; } @Override public String description() { return NAME + "(" + field +":("+qfield+"))"; } @Override public FunctionValues getValues(Map context, LeafReaderContext readerContext) throws IOException { final BinaryDocValues terms = DocValues.getBinary(readerContext.reader(), field); final IndexReader top = ReaderUtil.getTopLevelContext(readerContext).reader(); Terms t = MultiTerms.getTerms(top, qfield); final TermsEnum termsEnum = t == null ? TermsEnum.EMPTY : t.iterator(); return new IntDocValues(this) { int lastDocID = -1; @Override public int intVal(int doc) throws IOException { if (doc < lastDocID) { throw new IllegalArgumentException("docs were sent out-of-order: lastDocID=" + lastDocID + " vs docID=" + doc); } lastDocID = doc; int curDocID = terms.docID(); if (doc > curDocID) { curDocID = terms.advance(doc); } if (doc == curDocID) { BytesRef term = terms.binaryValue(); if (termsEnum.seekExact(term)) { return termsEnum.docFreq(); } } return 0; } }; } @Override public boolean equals(Object o) { if (o.getClass() != JoinDocFreqValueSource.class) return false; JoinDocFreqValueSource other = (JoinDocFreqValueSource)o; if( !qfield.equals( other.qfield ) ) return false; return super.equals(other); } @Override public int hashCode() { return qfield.hashCode() + super.hashCode(); } }