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Lucene example source code file (TermInfosWriter.java)

This example Lucene source code file (TermInfosWriter.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

closeable, fieldinfos, fieldinfos, format, format_version_utf8_length_in_bytes, indexoutput, io, ioexception, ioexception, string, string, terminfo, terminfoswriter, terminfoswriter, utf-8

The Lucene TermInfosWriter.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.Closeable;
import java.io.IOException;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.UnicodeUtil;
import org.apache.lucene.util.ArrayUtil;


/** This stores a monotonically increasing set of <Term, TermInfo> pairs in a
  Directory.  A TermInfos can be written once, in order.  */

final class TermInfosWriter implements Closeable {
  /** The file format version, a negative number. */
  public static final int FORMAT = -3;

  // Changed strings to true utf8 with length-in-bytes not
  // length-in-chars
  public static final int FORMAT_VERSION_UTF8_LENGTH_IN_BYTES = -4;

  // NOTE: always change this if you switch to a new format!
  public static final int FORMAT_CURRENT = FORMAT_VERSION_UTF8_LENGTH_IN_BYTES;

  private FieldInfos fieldInfos;
  private IndexOutput output;
  private TermInfo lastTi = new TermInfo();
  private long size;

  // TODO: the default values for these two parameters should be settable from
  // IndexWriter.  However, once that's done, folks will start setting them to
  // ridiculous values and complaining that things don't work well, as with
  // mergeFactor.  So, let's wait until a number of folks find that alternate
  // values work better.  Note that both of these values are stored in the
  // segment, so that it's safe to change these w/o rebuilding all indexes.

  /** Expert: The fraction of terms in the "dictionary" which should be stored
   * in RAM.  Smaller values use more memory, but make searching slightly
   * faster, while larger values use less memory and make searching slightly
   * slower.  Searching is typically not dominated by dictionary lookup, so
   * tweaking this is rarely useful.*/
  int indexInterval = 128;

  /** Expert: The fraction of {@link TermDocs} entries stored in skip tables,
   * used to accelerate {@link TermDocs#skipTo(int)}.  Larger values result in
   * smaller indexes, greater acceleration, but fewer accelerable cases, while
   * smaller values result in bigger indexes, less acceleration and more
   * accelerable cases. More detailed experiments would be useful here. */
  int skipInterval = 16;
  
  /** Expert: The maximum number of skip levels. Smaller values result in 
   * slightly smaller indexes, but slower skipping in big posting lists.
   */
  int maxSkipLevels = 10;

  private long lastIndexPointer;
  private boolean isIndex;
  private byte[] lastTermBytes = new byte[10];
  private int lastTermBytesLength = 0;
  private int lastFieldNumber = -1;

  private TermInfosWriter other;
  private UnicodeUtil.UTF8Result utf8Result = new UnicodeUtil.UTF8Result();

  TermInfosWriter(Directory directory, String segment, FieldInfos fis,
                  int interval)
       throws IOException {
    initialize(directory, segment, fis, interval, false);
    boolean success = false;
    try {
      other = new TermInfosWriter(directory, segment, fis, interval, true);
      other.other = this;
      success = true;
    } finally {
      if (!success) {
        IOUtils.closeSafely(true, output, other);
      }
    }
  }

  private TermInfosWriter(Directory directory, String segment, FieldInfos fis,
                          int interval, boolean isIndex) throws IOException {
    initialize(directory, segment, fis, interval, isIndex);
  }

  private void initialize(Directory directory, String segment, FieldInfos fis,
                          int interval, boolean isi) throws IOException {
    indexInterval = interval;
    fieldInfos = fis;
    isIndex = isi;
    output = directory.createOutput(segment + (isIndex ? ".tii" : ".tis"));
    boolean success = false;
    try {
      output.writeInt(FORMAT_CURRENT);              // write format
      output.writeLong(0);                          // leave space for size
      output.writeInt(indexInterval);               // write indexInterval
      output.writeInt(skipInterval);                // write skipInterval
      output.writeInt(maxSkipLevels);               // write maxSkipLevels
      assert initUTF16Results();
      success = true;
    } finally {
      if (!success) {
        IOUtils.closeSafely(true, output);
      }
    }
  }

  void add(Term term, TermInfo ti) throws IOException {
    UnicodeUtil.UTF16toUTF8(term.text, 0, term.text.length(), utf8Result);
    add(fieldInfos.fieldNumber(term.field), utf8Result.result, utf8Result.length, ti);
  }

  // Currently used only by assert statements
  UnicodeUtil.UTF16Result utf16Result1;
  UnicodeUtil.UTF16Result utf16Result2;

  // Currently used only by assert statements
  private boolean initUTF16Results() {
    utf16Result1 = new UnicodeUtil.UTF16Result();
    utf16Result2 = new UnicodeUtil.UTF16Result();
    return true;
  }

  // Currently used only by assert statement
  private int compareToLastTerm(int fieldNumber, byte[] termBytes, int termBytesLength) {

    if (lastFieldNumber != fieldNumber) {
      final int cmp = fieldInfos.fieldName(lastFieldNumber).compareTo(fieldInfos.fieldName(fieldNumber));
      // If there is a field named "" (empty string) then we
      // will get 0 on this comparison, yet, it's "OK".  But
      // it's not OK if two different field numbers map to
      // the same name.
      if (cmp != 0 || lastFieldNumber != -1)
        return cmp;
    }

    UnicodeUtil.UTF8toUTF16(lastTermBytes, 0, lastTermBytesLength, utf16Result1);
    UnicodeUtil.UTF8toUTF16(termBytes, 0, termBytesLength, utf16Result2);
    final int len;
    if (utf16Result1.length < utf16Result2.length)
      len = utf16Result1.length;
    else
      len = utf16Result2.length;

    for(int i=0;i<len;i++) {
      final char ch1 = utf16Result1.result[i];
      final char ch2 = utf16Result2.result[i];
      if (ch1 != ch2)
        return ch1-ch2;
    }
    return utf16Result1.length - utf16Result2.length;
  }

  /** Adds a new < pair to the set.
    Term must be lexicographically greater than all previous Terms added.
    TermInfo pointers must be positive and greater than all previous.*/
  void add(int fieldNumber, byte[] termBytes, int termBytesLength, TermInfo ti)
    throws IOException {

    assert compareToLastTerm(fieldNumber, termBytes, termBytesLength) < 0 ||
      (isIndex && termBytesLength == 0 && lastTermBytesLength == 0) :
      "Terms are out of order: field=" + fieldInfos.fieldName(fieldNumber) + " (number " + fieldNumber + ")" +
        " lastField=" + fieldInfos.fieldName(lastFieldNumber) + " (number " + lastFieldNumber + ")" +
        " text=" + new String(termBytes, 0, termBytesLength, "UTF-8") + " lastText=" + new String(lastTermBytes, 0, lastTermBytesLength, "UTF-8");

    assert ti.freqPointer >= lastTi.freqPointer: "freqPointer out of order (" + ti.freqPointer + " < " + lastTi.freqPointer + ")";
    assert ti.proxPointer >= lastTi.proxPointer: "proxPointer out of order (" + ti.proxPointer + " < " + lastTi.proxPointer + ")";

    if (!isIndex && size % indexInterval == 0)
      other.add(lastFieldNumber, lastTermBytes, lastTermBytesLength, lastTi);                      // add an index term

    writeTerm(fieldNumber, termBytes, termBytesLength);                        // write term

    output.writeVInt(ti.docFreq);                       // write doc freq
    output.writeVLong(ti.freqPointer - lastTi.freqPointer); // write pointers
    output.writeVLong(ti.proxPointer - lastTi.proxPointer);

    if (ti.docFreq >= skipInterval) {
      output.writeVInt(ti.skipOffset);
    }

    if (isIndex) {
      output.writeVLong(other.output.getFilePointer() - lastIndexPointer);
      lastIndexPointer = other.output.getFilePointer(); // write pointer
    }

    lastFieldNumber = fieldNumber;
    lastTi.set(ti);
    size++;
  }

  private void writeTerm(int fieldNumber, byte[] termBytes, int termBytesLength)
       throws IOException {

    // TODO: UTF16toUTF8 could tell us this prefix
    // Compute prefix in common with last term:
    int start = 0;
    final int limit = termBytesLength < lastTermBytesLength ? termBytesLength : lastTermBytesLength;
    while(start < limit) {
      if (termBytes[start] != lastTermBytes[start])
        break;
      start++;
    }

    final int length = termBytesLength - start;
    output.writeVInt(start);                     // write shared prefix length
    output.writeVInt(length);                  // write delta length
    output.writeBytes(termBytes, start, length);  // write delta bytes
    output.writeVInt(fieldNumber); // write field num
    if (lastTermBytes.length < termBytesLength) {
      lastTermBytes = ArrayUtil.grow(lastTermBytes, termBytesLength);
    }
    System.arraycopy(termBytes, start, lastTermBytes, start, length);
    lastTermBytesLength = termBytesLength;
  }

  /** Called to complete TermInfos creation. */
  public void close() throws IOException {
    try {
      output.seek(4);          // write size after format
      output.writeLong(size);
    } finally {
      try {
        output.close();
      } finally {
        if (!isIndex) {
          other.close();
        }
      }
    }

  }

}

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