/**
* 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.mahout.utils.vectors.lucene;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.MultiFields;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.util.BytesRef;
import org.apache.mahout.utils.vectors.TermEntry;
import org.apache.mahout.utils.vectors.TermInfo;
import java.io.IOException;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* Caches TermEntries from a single field. Materializes all values in the TermEnum to memory (much like FieldCache)
*/
public class CachedTermInfo implements TermInfo {
private final Map<String, TermEntry> termEntries;
private final String field;
public CachedTermInfo(IndexReader reader, String field, int minDf, int maxDfPercent) throws IOException {
this.field = field;
Terms t = MultiFields.getTerms(reader, field);
TermsEnum te = t.iterator(null);
int numDocs = reader.numDocs();
double percent = numDocs * maxDfPercent / 100.0;
//Should we use a linked hash map so that we know terms are in order?
termEntries = new LinkedHashMap<String, TermEntry>();
int count = 0;
BytesRef text;
while ((text = te.next()) != null) {
int df = te.docFreq();
if (df < minDf || df > percent) {
continue;
}
TermEntry entry = new TermEntry(text.utf8ToString(), count++, df);
termEntries.put(entry.getTerm(), entry);
}
}
@Override
public int totalTerms(String field) {
return termEntries.size();
}
@Override
public TermEntry getTermEntry(String field, String term) {
if (!this.field.equals(field)) {
return null;
}
return termEntries.get(term);
}
@Override
public Iterator<TermEntry> getAllEntries() {
return termEntries.values().iterator();
}
}