lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene50/compressing/Lucene50CompressingTermVectorsFormat.java

/*
 * 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.backward_codecs.lucene50.compressing;

import java.io.IOException;
import org.apache.lucene.codecs.CodecUtil;
import org.apache.lucene.codecs.StoredFieldsFormat;
import org.apache.lucene.codecs.TermVectorsFormat;
import org.apache.lucene.codecs.TermVectorsReader;
import org.apache.lucene.codecs.TermVectorsWriter;
import org.apache.lucene.codecs.compressing.CompressionMode;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.SegmentInfo;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;

/**
 * A {@link TermVectorsFormat} that compresses chunks of documents together in order to improve the
 * compression ratio.
 *
 * @lucene.experimental
 */
public class Lucene50CompressingTermVectorsFormat extends TermVectorsFormat {

  /** format name */
  protected final String formatName;
  /** segment suffix */
  protected final String segmentSuffix;
  /** compression mode */
  protected final CompressionMode compressionMode;
  /** chunk size */
  protected final int chunkSize;
  /** block size */
  protected final int blockSize;

  /**
   * Create a new {@link Lucene50CompressingTermVectorsFormat}.
   *
   * <p><code>formatName</code> is the name of the format. This name will be used in the file
   * formats to perform {@link CodecUtil#checkIndexHeader codec header checks}.
   *
   * <p>The <code>compressionMode</code> parameter allows you to choose between compression
   * algorithms that have various compression and decompression speeds so that you can pick the one
   * that best fits your indexing and searching throughput. You should never instantiate two {@link
   * Lucene50CompressingTermVectorsFormat}s that have the same name but different {@link
   * CompressionMode}s.
   *
   * <p><code>chunkSize</code> is the minimum byte size of a chunk of documents. Higher values of
   * <code>chunkSize</code> should improve the compression ratio but will require more memory at
   * indexing time and might make document loading a little slower (depending on the size of your OS
   * cache compared to the size of your index).
   *
   * @param formatName the name of the {@link StoredFieldsFormat}
   * @param segmentSuffix a suffix to append to files created by this format
   * @param compressionMode the {@link CompressionMode} to use
   * @param chunkSize the minimum number of bytes of a single chunk of stored documents
   * @param blockSize the number of chunks to store in an index block.
   * @see CompressionMode
   */
  public Lucene50CompressingTermVectorsFormat(
      String formatName,
      String segmentSuffix,
      CompressionMode compressionMode,
      int chunkSize,
      int blockSize) {
    this.formatName = formatName;
    this.segmentSuffix = segmentSuffix;
    this.compressionMode = compressionMode;
    if (chunkSize < 1) {
      throw new IllegalArgumentException("chunkSize must be >= 1");
    }
    this.chunkSize = chunkSize;
    if (blockSize < 1) {
      throw new IllegalArgumentException("blockSize must be >= 1");
    }
    this.blockSize = blockSize;
  }

  @Override
  public final TermVectorsReader vectorsReader(
      Directory directory, SegmentInfo segmentInfo, FieldInfos fieldInfos, IOContext context)
      throws IOException {
    return new Lucene50CompressingTermVectorsReader(
        directory, segmentInfo, segmentSuffix, fieldInfos, context, formatName, compressionMode);
  }

  @Override
  public TermVectorsWriter vectorsWriter(
      Directory directory, SegmentInfo segmentInfo, IOContext context) throws IOException {
    throw new UnsupportedOperationException("Old formats can't be used for writing");
  }

  @Override
  public String toString() {
    return getClass().getSimpleName()
        + "(compressionMode="
        + compressionMode
        + ", chunkSize="
        + chunkSize
        + ", blockSize="
        + blockSize
        + ")";
  }
}