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Lucene example source code file (BufferedDeletesStream.java)

This example Lucene source code file (BufferedDeletesStream.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

applydeletesresult, applydeletesresult, arraylist, arraylist, buffereddeletes, comparator, frozenbuffereddeletes, io, ioexception, list, list, queryandlimit, segmentreader, segmentreader, term, util

The Lucene BufferedDeletesStream.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.PrintStream;
import java.util.List;
import java.util.ArrayList;
import java.util.Date;
import java.util.Comparator;
import java.util.Collections;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;

import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.QueryWrapperFilter;

/* Tracks the stream of {@link BuffereDeletes}.
 * When DocumensWriter flushes, its buffered
 * deletes are appended to this stream.  We later
 * apply these deletes (resolve them to the actual
 * docIDs, per segment) when a merge is started
 * (only to the to-be-merged segments).  We
 * also apply to all segments when NRT reader is pulled,
 * commit/close is called, or when too many deletes are
 * buffered and must be flushed (by RAM usage or by count).
 *
 * Each packet is assigned a generation, and each flushed or
 * merged segment is also assigned a generation, so we can
 * track which BufferedDeletes packets to apply to any given
 * segment. */

class BufferedDeletesStream {

  // TODO: maybe linked list?
  private final List<FrozenBufferedDeletes> deletes = new ArrayList();

  // Starts at 1 so that SegmentInfos that have never had
  // deletes applied (whose bufferedDelGen defaults to 0)
  // will be correct:
  private long nextGen = 1;

  // used only by assert
  private Term lastDeleteTerm;
  
  private PrintStream infoStream;
  private final AtomicLong bytesUsed = new AtomicLong();
  private final AtomicInteger numTerms = new AtomicInteger();
  private final int messageID;

  public BufferedDeletesStream(int messageID) {
    this.messageID = messageID;
  }

  private synchronized void message(String message) {
    if (infoStream != null) {
      infoStream.println("BD " + messageID + " [" + new Date() + "; " + Thread.currentThread().getName() + "]: " + message);
    }
  }
  
  public synchronized void setInfoStream(PrintStream infoStream) {
    this.infoStream = infoStream;
  }

  // Appends a new packet of buffered deletes to the stream,
  // setting its generation:
  public synchronized void push(FrozenBufferedDeletes packet) {
    assert packet.any();
    assert checkDeleteStats();    
    assert packet.gen < nextGen;
    deletes.add(packet);
    numTerms.addAndGet(packet.numTermDeletes);
    bytesUsed.addAndGet(packet.bytesUsed);
    if (infoStream != null) {
      message("push deletes " + packet + " delGen=" + packet.gen + " packetCount=" + deletes.size());
    }
    assert checkDeleteStats();    
  }
    
  public synchronized void clear() {
    deletes.clear();
    nextGen = 1;
    numTerms.set(0);
    bytesUsed.set(0);
  }

  public boolean any() {
    return bytesUsed.get() != 0;
  }

  public int numTerms() {
    return numTerms.get();
  }

  public long bytesUsed() {
    return bytesUsed.get();
  }

  public static class ApplyDeletesResult {
    // True if any actual deletes took place:
    public final boolean anyDeletes;

    // Current gen, for the merged segment:
    public final long gen;

    // If non-null, contains segments that are 100% deleted
    public final List<SegmentInfo> allDeleted;

    ApplyDeletesResult(boolean anyDeletes, long gen, List<SegmentInfo> allDeleted) {
      this.anyDeletes = anyDeletes;
      this.gen = gen;
      this.allDeleted = allDeleted;
    }
  }

  // Sorts SegmentInfos from smallest to biggest bufferedDelGen:
  private static final Comparator<SegmentInfo> sortByDelGen = new Comparator() {
    // @Override -- not until Java 1.6
    public int compare(SegmentInfo si1, SegmentInfo si2) {
      final long cmp = si1.getBufferedDeletesGen() - si2.getBufferedDeletesGen();
      if (cmp > 0) {
        return 1;
      } else if (cmp < 0) {
        return -1;
      } else {
        return 0;
      }
    }

    @Override
    public boolean equals(Object other) {
      return sortByDelGen == other;
    }
  };

  /** Resolves the buffered deleted Term/Query/docIDs, into
   *  actual deleted docIDs in the deletedDocs BitVector for
   *  each SegmentReader. */
  public synchronized ApplyDeletesResult applyDeletes(IndexWriter.ReaderPool readerPool, List<SegmentInfo> infos) throws IOException {
    final long t0 = System.currentTimeMillis();

    if (infos.size() == 0) {
      return new ApplyDeletesResult(false, nextGen++, null);
    }

    assert checkDeleteStats();

    if (!any()) {
      message("applyDeletes: no deletes; skipping");
      return new ApplyDeletesResult(false, nextGen++, null);
    }

    if (infoStream != null) {
      message("applyDeletes: infos=" + infos + " packetCount=" + deletes.size());
    }

    List<SegmentInfo> infos2 = new ArrayList();
    infos2.addAll(infos);
    Collections.sort(infos2, sortByDelGen);

    BufferedDeletes coalescedDeletes = null;
    boolean anyNewDeletes = false;

    int infosIDX = infos2.size()-1;
    int delIDX = deletes.size()-1;

    List<SegmentInfo> allDeleted = null;

    while (infosIDX >= 0) {
      //System.out.println("BD: cycle delIDX=" + delIDX + " infoIDX=" + infosIDX);

      final FrozenBufferedDeletes packet = delIDX >= 0 ? deletes.get(delIDX) : null;
      final SegmentInfo info = infos2.get(infosIDX);
      final long segGen = info.getBufferedDeletesGen();

      if (packet != null && segGen < packet.gen) {
        //System.out.println("  coalesce");
        if (coalescedDeletes == null) {
          coalescedDeletes = new BufferedDeletes(true);
        }
        coalescedDeletes.update(packet);
        delIDX--;
      } else if (packet != null && segGen == packet.gen) {
        //System.out.println("  eq");

        // Lock order: IW -> BD -> RP
        assert readerPool.infoIsLive(info);
        SegmentReader reader = readerPool.get(info, false);
        int delCount = 0;
        final boolean segAllDeletes;
        try {
          if (coalescedDeletes != null) {
            //System.out.println("    del coalesced");
            delCount += applyTermDeletes(coalescedDeletes.termsIterable(), reader);
            delCount += applyQueryDeletes(coalescedDeletes.queriesIterable(), reader);
          }
          //System.out.println("    del exact");
          // Don't delete by Term here; DocumentsWriter
          // already did that on flush:
          delCount += applyQueryDeletes(packet.queriesIterable(), reader);
          segAllDeletes = reader.numDocs() == 0;
        } finally {
          readerPool.release(reader);
        }
        anyNewDeletes |= delCount > 0;

        if (segAllDeletes) {
          if (allDeleted == null) {
            allDeleted = new ArrayList<SegmentInfo>();
          }
          allDeleted.add(info);
        }

        if (infoStream != null) {
          message("seg=" + info + " segGen=" + segGen + " segDeletes=[" + packet + "]; coalesced deletes=[" + (coalescedDeletes == null ? "null" : coalescedDeletes) + "] delCount=" + delCount + (segAllDeletes ? " 100% deleted" : ""));
        }

        if (coalescedDeletes == null) {
          coalescedDeletes = new BufferedDeletes(true);
        }
        coalescedDeletes.update(packet);
        delIDX--;
        infosIDX--;
        info.setBufferedDeletesGen(nextGen);

      } else {
        //System.out.println("  gt");

        if (coalescedDeletes != null) {
          // Lock order: IW -> BD -> RP
          assert readerPool.infoIsLive(info);
          SegmentReader reader = readerPool.get(info, false);
          int delCount = 0;
          final boolean segAllDeletes;
          try {
            delCount += applyTermDeletes(coalescedDeletes.termsIterable(), reader);
            delCount += applyQueryDeletes(coalescedDeletes.queriesIterable(), reader);
            segAllDeletes = reader.numDocs() == 0;
          } finally {
            readerPool.release(reader);
          }
          anyNewDeletes |= delCount > 0;

          if (segAllDeletes) {
            if (allDeleted == null) {
              allDeleted = new ArrayList<SegmentInfo>();
            }
            allDeleted.add(info);
          }

          if (infoStream != null) {
            message("seg=" + info + " segGen=" + segGen + " coalesced deletes=[" + (coalescedDeletes == null ? "null" : coalescedDeletes) + "] delCount=" + delCount + (segAllDeletes ? " 100% deleted" : ""));
          }
        }
        info.setBufferedDeletesGen(nextGen);

        infosIDX--;
      }
    }

    assert checkDeleteStats();
    if (infoStream != null) {
      message("applyDeletes took " + (System.currentTimeMillis()-t0) + " msec");
    }
    // assert infos != segmentInfos || !any() : "infos=" + infos + " segmentInfos=" + segmentInfos + " any=" + any;
    
    return new ApplyDeletesResult(anyNewDeletes, nextGen++, allDeleted);
  }

  public synchronized long getNextGen() {
    return nextGen++;
  }

  // Lock order IW -> BD
  /* Removes any BufferedDeletes that we no longer need to
   * store because all segments in the index have had the
   * deletes applied. */
  public synchronized void prune(SegmentInfos segmentInfos) {
    assert checkDeleteStats();
    long minGen = Long.MAX_VALUE;
    for(SegmentInfo info : segmentInfos) {
      minGen = Math.min(info.getBufferedDeletesGen(), minGen);
    }

    if (infoStream != null) {
      message("prune sis=" + segmentInfos + " minGen=" + minGen + " packetCount=" + deletes.size());
    }

    final int limit = deletes.size();
    for(int delIDX=0;delIDX<limit;delIDX++) {
      if (deletes.get(delIDX).gen >= minGen) {
        prune(delIDX);
        assert checkDeleteStats();
        return;
      }
    }

    // All deletes pruned
    prune(limit);
    assert !any();
    assert checkDeleteStats();
  }

  private synchronized void prune(int count) {
    if (count > 0) {
      if (infoStream != null) {
        message("pruneDeletes: prune " + count + " packets; " + (deletes.size() - count) + " packets remain");
      }
      for(int delIDX=0;delIDX<count;delIDX++) {
        final FrozenBufferedDeletes packet = deletes.get(delIDX);
        numTerms.addAndGet(-packet.numTermDeletes);
        assert numTerms.get() >= 0;
        bytesUsed.addAndGet(-packet.bytesUsed);
        assert bytesUsed.get() >= 0;
      }
      deletes.subList(0, count).clear();
    }
  }

  // Delete by Term
  private synchronized long applyTermDeletes(Iterable<Term> termsIter, SegmentReader reader) throws IOException {
    long delCount = 0;
        
    assert checkDeleteTerm(null);
    
    final TermDocs docs = reader.termDocs();

    for (Term term : termsIter) {
        
      // Since we visit terms sorted, we gain performance
      // by re-using the same TermsEnum and seeking only
      // forwards
      assert checkDeleteTerm(term);
      docs.seek(term);
          
      while (docs.next()) {
        final int docID = docs.doc();
        reader.deleteDocument(docID);
        // TODO: we could/should change
        // reader.deleteDocument to return boolean
        // true if it did in fact delete, because here
        // we could be deleting an already-deleted doc
        // which makes this an upper bound:
        delCount++;
      }
    }

    return delCount;
  }

  public static class QueryAndLimit {
    public final Query query;
    public final int limit;
    public QueryAndLimit(Query query, int limit) {
      this.query = query;       
      this.limit = limit;
    }
  }

  // Delete by query
  private synchronized long applyQueryDeletes(Iterable<QueryAndLimit> queriesIter, SegmentReader reader) throws IOException {
    long delCount = 0;

    for (QueryAndLimit ent : queriesIter) {
      Query query = ent.query;
      int limit = ent.limit;
      final DocIdSet docs = new QueryWrapperFilter(query).getDocIdSet(reader);
      if (docs != null) {
        final DocIdSetIterator it = docs.iterator();
        if (it != null) {
          while(true)  {
            int doc = it.nextDoc();
            if (doc >= limit)
              break;

            reader.deleteDocument(doc);
            // TODO: we could/should change
            // reader.deleteDocument to return boolean
            // true if it did in fact delete, because here
            // we could be deleting an already-deleted doc
            // which makes this an upper bound:
            delCount++;
          }
        }
      }
    }

    return delCount;
  }

  // used only by assert
  private boolean checkDeleteTerm(Term term) {
    if (term != null) {
      assert lastDeleteTerm == null || term.compareTo(lastDeleteTerm) > 0: "lastTerm=" + lastDeleteTerm + " vs term=" + term;
    }
    lastDeleteTerm = term;
    return true;
  }
  
  // only for assert
  private boolean checkDeleteStats() {
    int numTerms2 = 0;
    long bytesUsed2 = 0;
    for(FrozenBufferedDeletes packet : deletes) {
      numTerms2 += packet.numTermDeletes;
      bytesUsed2 += packet.bytesUsed;
    }
    assert numTerms2 == numTerms.get(): "numTerms2=" + numTerms2 + " vs " + numTerms.get();
    assert bytesUsed2 == bytesUsed.get(): "bytesUsed2=" + bytesUsed2 + " vs " + bytesUsed;
    return true;
  }
}

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