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Lucene example source code file (TestMultiLevelSkipList.java)

This example Lucene source code file (TestMultiLevelSkipList.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

countingstream, countingstream, indexinput, indexwriter, io, ioexception, ioexception, override, override, payloadfilter, payloadfilter, ramdirectory, segmenttermpositions, term, wrong

The Lucene TestMultiLevelSkipList.java source code

package org.apache.lucene.index;

/**
 * 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.io.Reader;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.LowerCaseTokenizer;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.PayloadAttribute;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field.Index;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.LuceneTestCase;

/**
 * This testcase tests whether multi-level skipping is being used
 * to reduce I/O while skipping through posting lists.
 * 
 * Skipping in general is already covered by several other
 * testcases.
 * 
 */
public class TestMultiLevelSkipList extends LuceneTestCase {

  public void testSimpleSkip() throws IOException {
    RAMDirectory dir = new RAMDirectory();
    IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(TEST_VERSION_CURRENT, new PayloadAnalyzer()).setMergePolicy(newLogMergePolicy()));
    Term term = new Term("test", "a");
    for (int i = 0; i < 5000; i++) {
      Document d1 = new Document();
      d1.add(newField(term.field(), term.text(), Store.NO, Index.ANALYZED));
      writer.addDocument(d1);
    }
    writer.commit();
    writer.optimize();
    writer.close();

    IndexReader reader = SegmentReader.getOnlySegmentReader(dir);
    SegmentTermPositions tp = (SegmentTermPositions) reader.termPositions();
    tp.freqStream = new CountingStream(tp.freqStream);

    for (int i = 0; i < 2; i++) {
      counter = 0;
      tp.seek(term);

      checkSkipTo(tp, 14, 185); // no skips
      checkSkipTo(tp, 17, 190); // one skip on level 0
      checkSkipTo(tp, 287, 200); // one skip on level 1, two on level 0
    
      // this test would fail if we had only one skip level,
      // because than more bytes would be read from the freqStream
      checkSkipTo(tp, 4800, 250);// one skip on level 2
    }
  }

  public void checkSkipTo(TermPositions tp, int target, int maxCounter) throws IOException {
    tp.skipTo(target);
    if (maxCounter < counter) {
      fail("Too many bytes read: " + counter + " vs " + maxCounter);
    }

    assertEquals("Wrong document " + tp.doc() + " after skipTo target " + target, target, tp.doc());
    assertEquals("Frequency is not 1: " + tp.freq(), 1,tp.freq());
    tp.nextPosition();
    byte[] b = new byte[1];
    tp.getPayload(b, 0);
    assertEquals("Wrong payload for the target " + target + ": " + b[0], (byte) target, b[0]);
  }

  private static class PayloadAnalyzer extends Analyzer {
    @Override
    public TokenStream tokenStream(String fieldName, Reader reader) {
      return new PayloadFilter(new LowerCaseTokenizer(TEST_VERSION_CURRENT, reader));
    }

  }

  private static class PayloadFilter extends TokenFilter {
    static int count = 0;
    
    PayloadAttribute payloadAtt;
    
    protected PayloadFilter(TokenStream input) {
      super(input);
      payloadAtt = addAttribute(PayloadAttribute.class);
    }

    @Override
    public boolean incrementToken() throws IOException {
      boolean hasNext = input.incrementToken();
      if (hasNext) {
        payloadAtt.setPayload(new Payload(new byte[] { (byte) count++ }));
      } 
      return hasNext;
    }

  }

  private int counter = 0;

  // Simply extends IndexInput in a way that we are able to count the number
  // of bytes read
  class CountingStream extends IndexInput {
    private IndexInput input;

    CountingStream(IndexInput input) {
      this.input = input;
    }

    @Override
    public byte readByte() throws IOException {
      TestMultiLevelSkipList.this.counter++;
      return this.input.readByte();
    }

    @Override
    public void readBytes(byte[] b, int offset, int len) throws IOException {
      TestMultiLevelSkipList.this.counter += len;
      this.input.readBytes(b, offset, len);
    }

    @Override
    public void close() throws IOException {
      this.input.close();
    }

    @Override
    public long getFilePointer() {
      return this.input.getFilePointer();
    }

    @Override
    public void seek(long pos) throws IOException {
      this.input.seek(pos);
    }

    @Override
    public long length() {
      return this.input.length();
    }

    @Override
    public Object clone() {
      return new CountingStream((IndexInput) this.input.clone());
    }

  }
}

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