org.apache.mahout.utils.vectors.lucene.CachedTermInfo.java Source code

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Here is the source code for org.apache.mahout.utils.vectors.lucene.CachedTermInfo.java

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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.mahout.utils.vectors.lucene;

import com.google.common.collect.Maps;
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.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 = Maps.newLinkedHashMap();
        int count = 0;
        BytesRef text;
        while ((text = te.next()) != null) {
            int df = te.docFreq();
            if (df >= minDf && df <= percent) {
                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();
    }
}