GenerationFromSegmentsFileName() public static method

Parse the generation off the segments file name and return it.
public static GenerationFromSegmentsFileName ( string fileName ) : long
fileName string
return long
        /** @see IndexReader#listCommits */
        public new static ICollection <IndexCommitPoint> ListCommits(Directory dir)
        {
            string[] files = dir.List();
            if (files == null)
            {
                throw new System.IO.IOException("cannot read directory " + dir + ": list() returned null");
            }

            ICollection <IndexCommitPoint> commits = new List <IndexCommitPoint>();

            SegmentInfos latest = new SegmentInfos();

            latest.Read(dir);
            long currentGen = latest.GetGeneration();

            commits.Add(new ReaderCommit(latest, dir));

            for (int i = 0; i < files.Length; i++)
            {
                String fileName = files[i];

                if (fileName.StartsWith(IndexFileNames.SEGMENTS) &&
                    !fileName.Equals(IndexFileNames.SEGMENTS_GEN) &&
                    SegmentInfos.GenerationFromSegmentsFileName(fileName) < currentGen)
                {
                    SegmentInfos sis = new SegmentInfos();
                    try
                    {
                        // IOException allowed to throw there, in case
                        // segments_N is corrupt
                        sis.Read(dir, fileName);
                    }
                    catch (System.Exception)
                    {
                        // LUCENE-948: on NFS (and maybe others), if
                        // you have writers switching back and forth
                        // between machines, it's very likely that the
                        // dir listing will be stale and will claim a
                        // file segments_X exists when in fact it
                        // doesn't.  So, we catch this and handle it
                        // as if the file does not exist
                        sis = null;
                    }

                    if (sis != null)
                    {
                        commits.Add(new ReaderCommit(sis, dir));
                    }
                }
            }

            return(commits);
        }
Example #2
0
        private void VerifyCommitOrder <T>(IList <T> commits)
            where T : IndexCommit
        {
            if (commits.Count == 0)
            {
                return;
            }
            IndexCommit firstCommit = commits[0];
            long        last        = SegmentInfos.GenerationFromSegmentsFileName(firstCommit.SegmentsFileName);

            Assert.AreEqual(last, firstCommit.Generation);
            for (int i = 1; i < commits.Count; i++)
            {
                IndexCommit commit = commits[i];
                long        now    = SegmentInfos.GenerationFromSegmentsFileName(commit.SegmentsFileName);
                Assert.IsTrue(now > last, "SegmentInfos commits are out-of-order");
                Assert.AreEqual(now, commit.Generation);
                last = now;
            }
        }
Example #3
0
        private void  VerifyCommitOrder(System.Collections.IList commits)
        {
            IndexCommit firstCommit = ((IndexCommit)commits[0]);
            long        last        = SegmentInfos.GenerationFromSegmentsFileName(firstCommit.GetSegmentsFileName());

            Assert.AreEqual(last, firstCommit.GetGeneration());
            long lastVersion   = firstCommit.GetVersion();
            long lastTimestamp = firstCommit.GetTimestamp();

            for (int i = 1; i < commits.Count; i++)
            {
                IndexCommit commit       = ((IndexCommit)commits[i]);
                long        now          = SegmentInfos.GenerationFromSegmentsFileName(commit.GetSegmentsFileName());
                long        nowVersion   = commit.GetVersion();
                long        nowTimestamp = commit.GetTimestamp();
                Assert.IsTrue(now > last, "SegmentInfos commits are out-of-order");
                Assert.IsTrue(nowVersion > lastVersion, "SegmentInfos versions are out-of-order");
                Assert.IsTrue(nowTimestamp >= lastTimestamp, "SegmentInfos timestamps are out-of-order: now=" + nowTimestamp + " vs last=" + lastTimestamp);
                Assert.AreEqual(now, commit.GetGeneration());
                last          = now;
                lastVersion   = nowVersion;
                lastTimestamp = nowTimestamp;
            }
        }
        private void  VerifyCommitOrder <T>(IList <T> commits) where T : IndexCommit
        {
            IndexCommit firstCommit = commits[0];
            long        last        = SegmentInfos.GenerationFromSegmentsFileName(firstCommit.SegmentsFileName);

            Assert.AreEqual(last, firstCommit.Generation);
            long lastVersion   = firstCommit.Version;
            long lastTimestamp = firstCommit.Timestamp;

            for (int i = 1; i < commits.Count; i++)
            {
                IndexCommit commit       = commits[i];
                long        now          = SegmentInfos.GenerationFromSegmentsFileName(commit.SegmentsFileName);
                long        nowVersion   = commit.Version;
                long        nowTimestamp = commit.Timestamp;
                Assert.IsTrue(now > last, "SegmentInfos commits are out-of-order");
                Assert.IsTrue(nowVersion > lastVersion, "SegmentInfos versions are out-of-order");
                Assert.IsTrue(nowTimestamp >= lastTimestamp, "SegmentInfos timestamps are out-of-order: now=" + nowTimestamp + " vs last=" + lastTimestamp);
                Assert.AreEqual(now, commit.Generation);
                last          = now;
                lastVersion   = nowVersion;
                lastTimestamp = nowTimestamp;
            }
        }
Example #5
0
        /// <summary>
        /// Initialize the deleter: find all previous commits in
        /// the <see cref="Directory"/>, incref the files they reference, call
        /// the policy to let it delete commits.  this will remove
        /// any files not referenced by any of the commits. </summary>
        /// <exception cref="IOException"> if there is a low-level IO error </exception>
        public IndexFileDeleter(Directory directory, IndexDeletionPolicy policy, SegmentInfos segmentInfos, InfoStream infoStream, IndexWriter writer, bool initialIndexExists)
        {
            this.infoStream = infoStream;
            this.writer     = writer;

            string currentSegmentsFile = segmentInfos.GetSegmentsFileName();

            if (infoStream.IsEnabled("IFD"))
            {
                infoStream.Message("IFD", "init: current segments file is \"" + currentSegmentsFile + "\"; deletionPolicy=" + policy);
            }

            this.policy    = policy;
            this.directory = directory;

            // First pass: walk the files and initialize our ref
            // counts:
            long currentGen = segmentInfos.Generation;

            CommitPoint currentCommitPoint = null;

            string[] files = null;
            try
            {
                files = directory.ListAll();
            }
#pragma warning disable 168
            catch (DirectoryNotFoundException e)
#pragma warning restore 168
            {
                // it means the directory is empty, so ignore it.
                files = new string[0];
            }

            if (currentSegmentsFile != null)
            {
                Regex r = IndexFileNames.CODEC_FILE_PATTERN;
                foreach (string fileName in files)
                {
                    if (!fileName.EndsWith("write.lock", StringComparison.Ordinal) && !fileName.Equals(IndexFileNames.SEGMENTS_GEN, StringComparison.Ordinal) &&
                        (r.IsMatch(fileName) || fileName.StartsWith(IndexFileNames.SEGMENTS, StringComparison.Ordinal)))
                    {
                        // Add this file to refCounts with initial count 0:
                        GetRefCount(fileName);

                        if (fileName.StartsWith(IndexFileNames.SEGMENTS, StringComparison.Ordinal))
                        {
                            // this is a commit (segments or segments_N), and
                            // it's valid (<= the max gen).  Load it, then
                            // incref all files it refers to:
                            if (infoStream.IsEnabled("IFD"))
                            {
                                infoStream.Message("IFD", "init: load commit \"" + fileName + "\"");
                            }
                            SegmentInfos sis = new SegmentInfos();
                            try
                            {
                                sis.Read(directory, fileName);
                            }
#pragma warning disable 168
                            catch (FileNotFoundException e)
#pragma warning restore 168
                            {
                                // LUCENE-948: on NFS (and maybe others), if
                                // you have writers switching back and forth
                                // between machines, it's very likely that the
                                // dir listing will be stale and will claim a
                                // file segments_X exists when in fact it
                                // doesn't.  So, we catch this and handle it
                                // as if the file does not exist
                                if (infoStream.IsEnabled("IFD"))
                                {
                                    infoStream.Message("IFD", "init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
                                }
                                sis = null;
                            }
                            // LUCENENET specific - .NET (thankfully) only has one FileNotFoundException, so we don't need this
                            //catch (NoSuchFileException)
                            //{
                            //    // LUCENE-948: on NFS (and maybe others), if
                            //    // you have writers switching back and forth
                            //    // between machines, it's very likely that the
                            //    // dir listing will be stale and will claim a
                            //    // file segments_X exists when in fact it
                            //    // doesn't.  So, we catch this and handle it
                            //    // as if the file does not exist
                            //    if (infoStream.IsEnabled("IFD"))
                            //    {
                            //        infoStream.Message("IFD", "init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
                            //    }
                            //    sis = null;
                            //}
                            // LUCENENET specific - since NoSuchDirectoryException subclasses FileNotFoundException
                            // in Lucene, we need to catch it here to be on the safe side.
                            catch (System.IO.DirectoryNotFoundException)
                            {
                                // LUCENE-948: on NFS (and maybe others), if
                                // you have writers switching back and forth
                                // between machines, it's very likely that the
                                // dir listing will be stale and will claim a
                                // file segments_X exists when in fact it
                                // doesn't.  So, we catch this and handle it
                                // as if the file does not exist
                                if (infoStream.IsEnabled("IFD"))
                                {
                                    infoStream.Message("IFD", "init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
                                }
                                sis = null;
                            }
                            catch (IOException /*e*/)
                            {
                                if (SegmentInfos.GenerationFromSegmentsFileName(fileName) <= currentGen && directory.FileLength(fileName) > 0)
                                {
                                    throw; // LUCENENET: CA2200: Rethrow to preserve stack details (https://docs.microsoft.com/en-us/visualstudio/code-quality/ca2200-rethrow-to-preserve-stack-details)
                                }
                                else
                                {
                                    // Most likely we are opening an index that
                                    // has an aborted "future" commit, so suppress
                                    // exc in this case
                                    sis = null;
                                }
                            }
                            if (sis != null)
                            {
                                CommitPoint commitPoint = new CommitPoint(commitsToDelete, directory, sis);
                                if (sis.Generation == segmentInfos.Generation)
                                {
                                    currentCommitPoint = commitPoint;
                                }
                                commits.Add(commitPoint);
                                IncRef(sis, true);

                                if (lastSegmentInfos == null || sis.Generation > lastSegmentInfos.Generation)
                                {
                                    lastSegmentInfos = sis;
                                }
                            }
                        }
                    }
                }
            }

            if (currentCommitPoint == null && currentSegmentsFile != null && initialIndexExists)
            {
                // We did not in fact see the segments_N file
                // corresponding to the segmentInfos that was passed
                // in.  Yet, it must exist, because our caller holds
                // the write lock.  this can happen when the directory
                // listing was stale (eg when index accessed via NFS
                // client with stale directory listing cache).  So we
                // try now to explicitly open this commit point:
                SegmentInfos sis = new SegmentInfos();
                try
                {
                    sis.Read(directory, currentSegmentsFile);
                }
                catch (IOException e)
                {
                    throw new CorruptIndexException("failed to locate current segments_N file \"" + currentSegmentsFile + "\"" + e.ToString(), e);
                }
                if (infoStream.IsEnabled("IFD"))
                {
                    infoStream.Message("IFD", "forced open of current segments file " + segmentInfos.GetSegmentsFileName());
                }
                currentCommitPoint = new CommitPoint(commitsToDelete, directory, sis);
                commits.Add(currentCommitPoint);
                IncRef(sis, true);
            }

            // We keep commits list in sorted order (oldest to newest):
            CollectionUtil.TimSort(commits);

            // Now delete anything with ref count at 0.  These are
            // presumably abandoned files eg due to crash of
            // IndexWriter.
            foreach (KeyValuePair <string, RefCount> entry in refCounts)
            {
                RefCount rc       = entry.Value;
                string   fileName = entry.Key;
                if (0 == rc.count)
                {
                    if (infoStream.IsEnabled("IFD"))
                    {
                        infoStream.Message("IFD", "init: removing unreferenced file \"" + fileName + "\"");
                    }
                    DeleteFile(fileName);
                }
            }

            // Finally, give policy a chance to remove things on
            // startup:
            this.policy.OnInit(commits);

            // Always protect the incoming segmentInfos since
            // sometime it may not be the most recent commit
            Checkpoint(segmentInfos, false);

            startingCommitDeleted = currentCommitPoint == null ? false : currentCommitPoint.IsDeleted;

            DeleteCommits();
        }
Example #6
0
        /// <summary> Initialize the deleter: find all previous commits in
        /// the Directory, incref the files they reference, call
        /// the policy to let it delete commits.  The incoming
        /// segmentInfos must have been loaded from a commit point
        /// and not yet modified.  This will remove any files not
        /// referenced by any of the commits.
        /// </summary>
        /// <throws>  CorruptIndexException if the index is corrupt </throws>
        /// <throws>  IOException if there is a low-level IO error </throws>
        public IndexFileDeleter(Directory directory, IndexDeletionPolicy policy, SegmentInfos segmentInfos, System.IO.TextWriter infoStream, DocumentsWriter docWriter)
        {
            this.docWriter  = docWriter;
            this.infoStream = infoStream;

            if (infoStream != null)
            {
                Message("init: current segments file is \"" + segmentInfos.GetCurrentSegmentFileName() + "\"; deletionPolicy=" + policy);
            }

            this.policy    = policy;
            this.directory = directory;

            // First pass: walk the files and initialize our ref
            // counts:
            long currentGen            = segmentInfos.GetGeneration();
            IndexFileNameFilter filter = IndexFileNameFilter.GetFilter();

            System.String[] files = directory.List();
            if (files == null)
            {
                throw new System.IO.IOException("cannot read directory " + directory + ": list() returned null");
            }

            CommitPoint currentCommitPoint = null;

            for (int i = 0; i < files.Length; i++)
            {
                System.String fileName = files[i];

                if (filter.Accept(null, fileName) && !fileName.Equals(IndexFileNames.SEGMENTS_GEN))
                {
                    // Add this file to refCounts with initial count 0:
                    GetRefCount(fileName);

                    if (fileName.StartsWith(IndexFileNames.SEGMENTS))
                    {
                        // This is a commit (segments or segments_N), and
                        // it's valid (<= the max gen).  Load it, then
                        // incref all files it refers to:
                        if (SegmentInfos.GenerationFromSegmentsFileName(fileName) <= currentGen)
                        {
                            if (infoStream != null)
                            {
                                Message("init: load commit \"" + fileName + "\"");
                            }
                            SegmentInfos sis = new SegmentInfos();
                            try
                            {
                                sis.Read(directory, fileName);
                            }
                            catch (System.IO.FileNotFoundException e)
                            {
                                // LUCENE-948: on NFS (and maybe others), if
                                // you have writers switching back and forth
                                // between machines, it's very likely that the
                                // dir listing will be stale and will claim a
                                // file segments_X exists when in fact it
                                // doesn't.  So, we catch this and handle it
                                // as if the file does not exist
                                if (infoStream != null)
                                {
                                    Message("init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
                                }
                                sis = null;
                            }
                            if (sis != null)
                            {
                                CommitPoint commitPoint = new CommitPoint(this, sis);
                                if (sis.GetGeneration() == segmentInfos.GetGeneration())
                                {
                                    currentCommitPoint = commitPoint;
                                }
                                commits.Add(commitPoint);
                                IncRef(sis, true);
                            }
                        }
                    }
                }
            }

            if (currentCommitPoint == null)
            {
                // We did not in fact see the segments_N file
                // corresponding to the segmentInfos that was passed
                // in.  Yet, it must exist, because our caller holds
                // the write lock.  This can happen when the directory
                // listing was stale (eg when index accessed via NFS
                // client with stale directory listing cache).  So we
                // try now to explicitly open this commit point:
                SegmentInfos sis = new SegmentInfos();
                try
                {
                    sis.Read(directory, segmentInfos.GetCurrentSegmentFileName());
                }
                catch (System.IO.IOException e)
                {
                    throw new CorruptIndexException("failed to locate current segments_N file");
                }
                if (infoStream != null)
                {
                    Message("forced open of current segments file " + segmentInfos.GetCurrentSegmentFileName());
                }
                currentCommitPoint = new CommitPoint(this, sis);
                commits.Add(currentCommitPoint);
                IncRef(sis, true);
            }

            // We keep commits list in sorted order (oldest to newest):
            commits.Sort();

            // Now delete anything with ref count at 0.  These are
            // presumably abandoned files eg due to crash of
            // IndexWriter.
            System.Collections.IEnumerator it = refCounts.Keys.GetEnumerator();
            while (it.MoveNext())
            {
                System.String fileName = (System.String)it.Current;
                RefCount      rc       = (RefCount)refCounts[fileName];
                if (0 == rc.count)
                {
                    if (infoStream != null)
                    {
                        Message("init: removing unreferenced file \"" + fileName + "\"");
                    }
                    DeleteFile(fileName);
                }
            }

            // Finally, give policy a chance to remove things on
            // startup:
            policy.OnInit(commits);

            // It's OK for the onInit to remove the current commit
            // point; we just have to checkpoint our in-memory
            // SegmentInfos to protect those files that it uses:
            if (currentCommitPoint.deleted)
            {
                Checkpoint(segmentInfos, false);
            }

            DeleteCommits();
        }
Example #7
0
        /// <summary>
        /// Returns all commit points that exist in the <see cref="Store.Directory"/>.
        /// Normally, because the default is
        /// <see cref="KeepOnlyLastCommitDeletionPolicy"/>, there would be only
        /// one commit point.  But if you're using a custom
        /// <see cref="IndexDeletionPolicy"/> then there could be many commits.
        /// Once you have a given commit, you can open a reader on
        /// it by calling <see cref="DirectoryReader.Open(IndexCommit)"/>
        /// There must be at least one commit in
        /// the <see cref="Store.Directory"/>, else this method throws
        /// <see cref="IndexNotFoundException"/>.  Note that if a commit is in
        /// progress while this method is running, that commit
        /// may or may not be returned.
        /// </summary>
        /// <returns> a sorted list of <see cref="Index.IndexCommit"/>s, from oldest
        /// to latest. </returns>
        public static IList <IndexCommit> ListCommits(Directory dir)
        {
            string[] files = dir.ListAll();

            List <IndexCommit> commits = new List <IndexCommit>();

            SegmentInfos latest = new SegmentInfos();

            latest.Read(dir);
            long currentGen = latest.Generation;

            commits.Add(new StandardDirectoryReader.ReaderCommit(latest, dir));

            for (int i = 0; i < files.Length; i++)
            {
                string fileName = files[i];

                if (fileName.StartsWith(IndexFileNames.SEGMENTS, StringComparison.Ordinal) && !fileName.Equals(IndexFileNames.SEGMENTS_GEN, StringComparison.Ordinal) && SegmentInfos.GenerationFromSegmentsFileName(fileName) < currentGen)
                {
                    SegmentInfos sis = new SegmentInfos();
                    try
                    {
                        // IOException allowed to throw there, in case
                        // segments_N is corrupt
                        sis.Read(dir, fileName);
                    }
                    catch (FileNotFoundException)
                    {
                        // LUCENE-948: on NFS (and maybe others), if
                        // you have writers switching back and forth
                        // between machines, it's very likely that the
                        // dir listing will be stale and will claim a
                        // file segments_X exists when in fact it
                        // doesn't.  So, we catch this and handle it
                        // as if the file does not exist
                        sis = null;
                    }
                    // LUCENENET specific - .NET (thankfully) only has one FileNotFoundException, so we don't need this
                    //catch (NoSuchFileException)
                    //{
                    //    sis = null;
                    //}
                    // LUCENENET specific - since NoSuchDirectoryException subclasses FileNotFoundException
                    // in Lucene, we need to catch it here to be on the safe side.
                    catch (System.IO.DirectoryNotFoundException)
                    {
                        // LUCENE-948: on NFS (and maybe others), if
                        // you have writers switching back and forth
                        // between machines, it's very likely that the
                        // dir listing will be stale and will claim a
                        // file segments_X exists when in fact it
                        // doesn't.  So, we catch this and handle it
                        // as if the file does not exist
                        sis = null;
                    }

                    if (sis != null)
                    {
                        commits.Add(new StandardDirectoryReader.ReaderCommit(sis, dir));
                    }
                }
            }

            // Ensure that the commit points are sorted in ascending order.
            commits.Sort();

            return(commits);
        }
Example #8
0
        /// <summary> Initialize the deleter: find all previous commits in
        /// the Directory, incref the files they reference, call
        /// the policy to let it delete commits.  This will remove
        /// any files not referenced by any of the commits.
        /// </summary>
        /// <throws>  CorruptIndexException if the index is corrupt </throws>
        /// <throws>  IOException if there is a low-level IO error </throws>
        public IndexFileDeleter(Directory directory, IndexDeletionPolicy policy, SegmentInfos segmentInfos, System.IO.StreamWriter infoStream, DocumentsWriter docWriter, HashSet <string> synced)
        {
            this.docWriter  = docWriter;
            this.infoStream = infoStream;
            this.synced     = synced;

            if (infoStream != null)
            {
                Message("init: current segments file is \"" + segmentInfos.GetCurrentSegmentFileName() + "\"; deletionPolicy=" + policy);
            }

            this.policy    = policy;
            this.directory = directory;

            // First pass: walk the files and initialize our ref
            // counts:
            long currentGen            = segmentInfos.Generation;
            IndexFileNameFilter filter = IndexFileNameFilter.Filter;

            System.String[] files = directory.ListAll();

            CommitPoint currentCommitPoint = null;

            for (int i = 0; i < files.Length; i++)
            {
                System.String fileName = files[i];

                if (filter.Accept(null, fileName) && !fileName.Equals(IndexFileNames.SEGMENTS_GEN))
                {
                    // Add this file to refCounts with initial count 0:
                    GetRefCount(fileName);

                    if (fileName.StartsWith(IndexFileNames.SEGMENTS))
                    {
                        // This is a commit (segments or segments_N), and
                        // it's valid (<= the max gen).  Load it, then
                        // incref all files it refers to:
                        if (infoStream != null)
                        {
                            Message("init: load commit \"" + fileName + "\"");
                        }
                        SegmentInfos sis = new SegmentInfos();
                        try
                        {
                            sis.Read(directory, fileName);
                        }
                        catch (System.IO.FileNotFoundException)
                        {
                            // LUCENE-948: on NFS (and maybe others), if
                            // you have writers switching back and forth
                            // between machines, it's very likely that the
                            // dir listing will be stale and will claim a
                            // file segments_X exists when in fact it
                            // doesn't.  So, we catch this and handle it
                            // as if the file does not exist
                            if (infoStream != null)
                            {
                                Message("init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
                            }
                            sis = null;
                        }
                        catch (System.IO.IOException)
                        {
                            if (SegmentInfos.GenerationFromSegmentsFileName(fileName) <= currentGen)
                            {
                                throw;
                            }
                            else
                            {
                                // Most likely we are opening an index that
                                // has an aborted "future" commit, so suppress
                                // exc in this case
                                sis = null;
                            }
                        }
                        if (sis != null)
                        {
                            CommitPoint commitPoint = new CommitPoint(this, commitsToDelete, directory, sis);
                            if (sis.Generation == segmentInfos.Generation)
                            {
                                currentCommitPoint = commitPoint;
                            }
                            commits.Add(commitPoint);
                            IncRef(sis, true);

                            if (lastSegmentInfos == null || sis.Generation > lastSegmentInfos.Generation)
                            {
                                lastSegmentInfos = sis;
                            }
                        }
                    }
                }
            }

            if (currentCommitPoint == null)
            {
                // We did not in fact see the segments_N file
                // corresponding to the segmentInfos that was passed
                // in.  Yet, it must exist, because our caller holds
                // the write lock.  This can happen when the directory
                // listing was stale (eg when index accessed via NFS
                // client with stale directory listing cache).  So we
                // try now to explicitly open this commit point:
                SegmentInfos sis = new SegmentInfos();
                try
                {
                    sis.Read(directory, segmentInfos.GetCurrentSegmentFileName());
                }
                catch (System.IO.IOException)
                {
                    throw new CorruptIndexException("failed to locate current segments_N file");
                }
                if (infoStream != null)
                {
                    Message("forced open of current segments file " + segmentInfos.GetCurrentSegmentFileName());
                }
                currentCommitPoint = new CommitPoint(this, commitsToDelete, directory, sis);
                commits.Add(currentCommitPoint);
                IncRef(sis, true);
            }

            // We keep commits list in sorted order (oldest to newest):
            commits.Sort();

            // Now delete anything with ref count at 0.  These are
            // presumably abandoned files eg due to crash of
            // IndexWriter.
            foreach (KeyValuePair <string, RefCount> entry in refCounts)
            {
                string   fileName = entry.Key;
                RefCount rc       = refCounts[fileName];
                if (0 == rc.count)
                {
                    if (infoStream != null)
                    {
                        Message("init: removing unreferenced file \"" + fileName + "\"");
                    }
                    DeleteFile(fileName);
                }
            }

            // Finally, give policy a chance to remove things on
            // startup:
            policy.OnInit(commits);

            // Always protect the incoming segmentInfos since
            // sometime it may not be the most recent commit
            Checkpoint(segmentInfos, false);

            startingCommitDeleted = currentCommitPoint.IsDeleted;

            DeleteCommits();
        }