multisegmentreader.java

lucene-2.4.0 是一个全文收索的工具包

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.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.apache.lucene.document.Document;
import org.apache.lucene.document.FieldSelector;
import org.apache.lucene.store.Directory;

/** 
 * An IndexReader which reads indexes with multiple segments.
 */
class MultiSegmentReader extends DirectoryIndexReader {
  protected SegmentReader[] subReaders;
  private int[] starts;                           // 1st docno for each segment
  private Map normsCache = new HashMap();
  private int maxDoc = 0;
  private int numDocs = -1;
  private boolean hasDeletions = false;

  /** Construct reading the named set of readers. */
  MultiSegmentReader(Directory directory, SegmentInfos sis, boolean closeDirectory, boolean readOnly) throws IOException {
    super(directory, sis, closeDirectory, readOnly);

    // To reduce the chance of hitting FileNotFound
    // (and having to retry), we open segments in
    // reverse because IndexWriter merges & deletes
    // the newest segments first.

    SegmentReader[] readers = new SegmentReader[sis.size()];
    for (int i = sis.size()-1; i >= 0; i--) {
      try {
        readers[i] = SegmentReader.get(readOnly, sis.info(i));
      } catch (IOException e) {
        // Close all readers we had opened:
        for(i++;i<sis.size();i++) {
          try {
            readers[i].close();
          } catch (IOException ignore) {
            // keep going - we want to clean up as much as possible
          }
        }
        throw e;
      }
    }

    initialize(readers);
  }

  /** This contructor is only used for {@link #reopen()} */
  MultiSegmentReader(Directory directory, SegmentInfos infos, boolean closeDirectory, SegmentReader[] oldReaders, int[] oldStarts, Map oldNormsCache, boolean readOnly) throws IOException {
    super(directory, infos, closeDirectory, readOnly);

    // we put the old SegmentReaders in a map, that allows us
    // to lookup a reader using its segment name
    Map segmentReaders = new HashMap();

    if (oldReaders != null) {
      // create a Map SegmentName->SegmentReader
      for (int i = 0; i < oldReaders.length; i++) {
        segmentReaders.put(oldReaders[i].getSegmentName(), new Integer(i));
      }
    }
    
    SegmentReader[] newReaders = new SegmentReader[infos.size()];
    
    // remember which readers are shared between the old and the re-opened
    // MultiSegmentReader - we have to incRef those readers
    boolean[] readerShared = new boolean[infos.size()];
    
    for (int i = infos.size() - 1; i>=0; i--) {
      // find SegmentReader for this segment
      Integer oldReaderIndex = (Integer) segmentReaders.get(infos.info(i).name);
      if (oldReaderIndex == null) {
        // this is a new segment, no old SegmentReader can be reused
        newReaders[i] = null;
      } else {
        // there is an old reader for this segment - we'll try to reopen it
        newReaders[i] = oldReaders[oldReaderIndex.intValue()];
      }

      boolean success = false;
      try {
        SegmentReader newReader;
        if (newReaders[i] == null || infos.info(i).getUseCompoundFile() != newReaders[i].getSegmentInfo().getUseCompoundFile()) {
          // this is a new reader; in case we hit an exception we can close it safely
          newReader = SegmentReader.get(readOnly, infos.info(i));
        } else {
          newReader = (SegmentReader) newReaders[i].reopenSegment(infos.info(i));
        }
        if (newReader == newReaders[i]) {
          // this reader will be shared between the old and the new one,
          // so we must incRef it
          readerShared[i] = true;
          newReader.incRef();
        } else {
          readerShared[i] = false;
          newReaders[i] = newReader;
        }
        success = true;
      } finally {
        if (!success) {
          for (i++; i < infos.size(); i++) {
            if (newReaders[i] != null) {
              try {
                if (!readerShared[i]) {
                  // this is a new subReader that is not used by the old one,
                  // we can close it
                  newReaders[i].close();
                } else {
                  // this subReader is also used by the old reader, so instead
                  // closing we must decRef it
                  newReaders[i].decRef();
                }
              } catch (IOException ignore) {
                // keep going - we want to clean up as much as possible
              }
            }
          }
        }
      }
    }    
    
    // initialize the readers to calculate maxDoc before we try to reuse the old normsCache
    initialize(newReaders);
    
    // try to copy unchanged norms from the old normsCache to the new one
    if (oldNormsCache != null) {
      Iterator it = oldNormsCache.entrySet().iterator();
      while (it.hasNext()) {
        Map.Entry entry = (Map.Entry) it.next();
        String field = (String) entry.getKey();
        if (!hasNorms(field)) {
          continue;
        }

        byte[] oldBytes = (byte[]) entry.getValue();

        byte[] bytes = new byte[maxDoc()];

        for (int i = 0; i < subReaders.length; i++) {
          Integer oldReaderIndex = ((Integer) segmentReaders.get(subReaders[i].getSegmentName()));

          // this SegmentReader was not re-opened, we can copy all of its norms 
          if (oldReaderIndex != null &&
               (oldReaders[oldReaderIndex.intValue()] == subReaders[i] 
                 || oldReaders[oldReaderIndex.intValue()].norms.get(field) == subReaders[i].norms.get(field))) {
            // we don't have to synchronize here: either this constructor is called from a SegmentReader,
            // in which case no old norms cache is present, or it is called from MultiReader.reopen(),
            // which is synchronized
            System.arraycopy(oldBytes, oldStarts[oldReaderIndex.intValue()], bytes, starts[i], starts[i+1] - starts[i]);
          } else {
            subReaders[i].norms(field, bytes, starts[i]);
          }
        }

        normsCache.put(field, bytes);      // update cache
      }
    }
  }

  private void initialize(SegmentReader[] subReaders) {
    this.subReaders = subReaders;
    starts = new int[subReaders.length + 1];    // build starts array
    for (int i = 0; i < subReaders.length; i++) {
      starts[i] = maxDoc;
      maxDoc += subReaders[i].maxDoc();      // compute maxDocs

      if (subReaders[i].hasDeletions())
        hasDeletions = true;
    }
    starts[subReaders.length] = maxDoc;
  }

  protected synchronized DirectoryIndexReader doReopen(SegmentInfos infos) throws CorruptIndexException, IOException {
    if (infos.size() == 1) {
      // The index has only one segment now, so we can't refresh the MultiSegmentReader.
      // Return a new [ReadOnly]SegmentReader instead
      return SegmentReader.get(readOnly, infos, infos.info(0), false);
    } else if (readOnly) {
      return new ReadOnlyMultiSegmentReader(directory, infos, closeDirectory, subReaders, starts, normsCache);
    } else {
      return new MultiSegmentReader(directory, infos, closeDirectory, subReaders, starts, normsCache, false);
    }            
  }

  public TermFreqVector[] getTermFreqVectors(int n) throws IOException {
    ensureOpen();
    int i = readerIndex(n);        // find segment num
    return subReaders[i].getTermFreqVectors(n - starts[i]); // dispatch to segment
  }

  public TermFreqVector getTermFreqVector(int n, String field)
      throws IOException {
    ensureOpen();
    int i = readerIndex(n);        // find segment num
    return subReaders[i].getTermFreqVector(n - starts[i], field);
  }


  public void getTermFreqVector(int docNumber, String field, TermVectorMapper mapper) throws IOException {
    ensureOpen();
    int i = readerIndex(docNumber);        // find segment num
    subReaders[i].getTermFreqVector(docNumber - starts[i], field, mapper);
  }

  public void getTermFreqVector(int docNumber, TermVectorMapper mapper) throws IOException {
    ensureOpen();
    int i = readerIndex(docNumber);        // find segment num
    subReaders[i].getTermFreqVector(docNumber - starts[i], mapper);
  }

  public boolean isOptimized() {
    return false;
  }
  
  public synchronized int numDocs() {
    // Don't call ensureOpen() here (it could affect performance)
    if (numDocs == -1) {        // check cache
      int n = 0;                // cache miss--recompute
      for (int i = 0; i < subReaders.length; i++)
        n += subReaders[i].numDocs();      // sum from readers
      numDocs = n;
    }
    return numDocs;
  }

  public int maxDoc() {
    // Don't call ensureOpen() here (it could affect performance)
    return maxDoc;
  }

  // inherit javadoc
  public Document document(int n, FieldSelector fieldSelector) throws CorruptIndexException, IOException {
    ensureOpen();
    int i = readerIndex(n);                          // find segment num
    return subReaders[i].document(n - starts[i], fieldSelector);    // dispatch to segment reader
  }

  public boolean isDeleted(int n) {
    // Don't call ensureOpen() here (it could affect performance)
    final int i = readerIndex(n);                           // find segment num
    return subReaders[i].isDeleted(n - starts[i]);    // dispatch to segment reader
  }

  public boolean hasDeletions() {
    // Don't call ensureOpen() here (it could affect performance)
    return hasDeletions;
  }

  protected void doDelete(int n) throws CorruptIndexException, IOException {
    numDocs = -1;                             // invalidate cache
    int i = readerIndex(n);                   // find segment num
    subReaders[i].deleteDocument(n - starts[i]);      // dispatch to segment reader
    hasDeletions = true;
  }

  protected void doUndeleteAll() throws CorruptIndexException, IOException {
    for (int i = 0; i < subReaders.length; i++)
      subReaders[i].undeleteAll();

    hasDeletions = false;
    numDocs = -1;                                 // invalidate cache
  }

  private int readerIndex(int n) {    // find reader for doc n:
    return readerIndex(n, this.starts, this.subReaders.length);
  }
  
  final static int readerIndex(int n, int[] starts, int numSubReaders) {    // find reader for doc n:
    int lo = 0;                                      // search starts array
    int hi = numSubReaders - 1;                  // for first element less

    while (hi >= lo) {
      int mid = (lo + hi) >> 1;
      int midValue = starts[mid];
      if (n < midValue)
        hi = mid - 1;
      else if (n > midValue)
        lo = mid + 1;
      else {                                      // found a match
        while (mid+1 < numSubReaders && starts[mid+1] == midValue) {
          mid++;                                  // scan to last match
        }
        return mid;
      }
    }
    return hi;
  }

  public boolean hasNorms(String field) throws IOException {
    ensureOpen();
    for (int i = 0; i < subReaders.length; i++) {
      if (subReaders[i].hasNorms(field)) return true;
    }
    return false;
  }

  private byte[] ones;
  private byte[] fakeNorms() {
    if (ones==null) ones=SegmentReader.createFakeNorms(maxDoc());
    return ones;
  }