LUCENE-1382: add opaque userData String passed to IndexWriter.commit, recorded into the segments file

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@706240 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -20,13 +20,19 @@ Bug fixes
 
 New features
 
-1. LUCENE-1411: Added expert API to open an IndexWriter on a prior
-   commit, obtained from IndexReader.listCommits.  This makes it
-   possible to rollback changes to an index even after you've closed
-   the IndexWriter that made the changes, assuming you are using an
-   IndexDeletionPolicy that keeps past commits around.  This is useful
-   when building transactional support on top of Lucene.  (Mike
-   McCandless)
+ 1. LUCENE-1411: Added expert API to open an IndexWriter on a prior
+    commit, obtained from IndexReader.listCommits.  This makes it
+    possible to rollback changes to an index even after you've closed
+    the IndexWriter that made the changes, assuming you are using an
+    IndexDeletionPolicy that keeps past commits around.  This is useful
+    when building transactional support on top of Lucene.  (Mike
+    McCandless)
+
+ 2. LUCENE-1382: Add an optional arbitrary String "commitUserData" to
+    IndexWriter.commit(), which is stored in the segments file and is
+    then retrievable via IndexReader.getCommitUserData instance and
+    static methods.  (Shalin Shekhar Mangar via Mike McCandless)
+
 
 Optimizations
 

src/java/org/apache/lucene/index/DirectoryIndexReader.java

@@ -169,6 +169,11 @@ abstract class DirectoryIndexReader extends IndexReader {
     return segmentInfos.getVersion();
   }
 
+  public String getCommitUserData() {
+    ensureOpen();
+    return segmentInfos.getUserData();
+  }
+
   /**
    * Check whether this IndexReader is still using the
    * current (i.e., most recently committed) version of the
@@ -367,11 +372,13 @@ abstract class DirectoryIndexReader extends IndexReader {
     long generation;
     long version;
     final boolean isOptimized;
+    final String userData;
 
     ReaderCommit(SegmentInfos infos, Directory dir) throws IOException {
       segmentsFileName = infos.getCurrentSegmentFileName();
       this.dir = dir;
       final int size = infos.size();
+      userData = infos.getUserData();
       files = new ArrayList(size);
       files.add(segmentsFileName);
       for(int i=0;i<size;i++) {
@@ -405,6 +412,9 @@ abstract class DirectoryIndexReader extends IndexReader {
     public boolean isDeleted() {
       return false;
     }
+    public String getUserData() {
+      return userData;
+    }
   }
 
   /**

src/java/org/apache/lucene/index/IndexCommit.java

@@ -101,14 +101,14 @@ public abstract class IndexCommit implements IndexCommitPoint {
   }
 
   /** Returns the version for this IndexCommit.  This is the
-      same value that {@link IndexReader#getVersion} would
-      return if it were opened on this commit. */
+   *  same value that {@link IndexReader#getVersion} would
+   *  return if it were opened on this commit. */
   public long getVersion() {
     throw new UnsupportedOperationException("This IndexCommit does not support this method.");
   }
 
   /** Returns the generation (the _N in segments_N) for this
-      IndexCommit */
+   *  IndexCommit */
   public long getGeneration() {
     throw new UnsupportedOperationException("This IndexCommit does not support this method.");
   }
@@ -120,4 +120,10 @@ public abstract class IndexCommit implements IndexCommitPoint {
   public long getTimestamp() throws IOException {
     return getDirectory().fileModified(getSegmentsFileName());
   }
+
+  /** Returns userData, previously passed to {@link
+   *  IndexWriter#commit(String)} for this commit.  */
+  public String getUserData() throws IOException {
+    throw new UnsupportedOperationException("This IndexCommit does not support this method.");
+  }
 }

src/java/org/apache/lucene/index/IndexFileDeleter.java

@@ -585,10 +585,12 @@ final class IndexFileDeleter {
     long version;
     long generation;
     final boolean isOptimized;
+    final String userData;
 
     public CommitPoint(Collection commitsToDelete, Directory directory, SegmentInfos segmentInfos) throws IOException {
       this.directory = directory;
       this.commitsToDelete = commitsToDelete;
+      userData = segmentInfos.getUserData();
       segmentsFileName = segmentInfos.getCurrentSegmentFileName();
       version = segmentInfos.getVersion();
       generation = segmentInfos.getGeneration();
@@ -629,6 +631,10 @@ final class IndexFileDeleter {
       return generation;
     }
 
+    public String getUserData() {
+      return userData;
+    }
+
     /**
      * Called only be the deletion policy, to remove this
      * commit point from the index.

src/java/org/apache/lucene/index/IndexReader.java

@@ -457,6 +457,24 @@ public abstract class IndexReader {
     return SegmentInfos.readCurrentVersion(directory);
   }
 
+  /**
+   * Reads commitUserData, previously passed to {@link
+   * IndexWriter#commit(String)}, from current index
+   * segments file.  This will return null if {@link
+   * IndexWriter#commit(String)} has never been called for
+   * this index.
+   * 
+   * @param directory where the index resides.
+   * @return commit userData.
+   * @throws CorruptIndexException if the index is corrupt
+   * @throws IOException if there is a low-level IO error
+   *
+   * @see #getCommitUserData()
+   */
+  public static String getCommitUserData(Directory directory) throws CorruptIndexException, IOException {
+    return SegmentInfos.readCurrentUserData(directory);
+  }
+
   /**
    * Version number when this IndexReader was opened. Not implemented in the IndexReader base class.
    * @throws UnsupportedOperationException unless overridden in subclass
@@ -465,6 +483,18 @@ public abstract class IndexReader {
     throw new UnsupportedOperationException("This reader does not support this method.");
   }
 
+  /**
+   * Retrieve the String userData optionally passed to
+   * IndexWriter#commit.  This will return null if {@link
+   * IndexWriter#commit(String)} has never been called for
+   * this index.
+   *
+   * @see #getCommitUserData(Directory)
+   */
+  public String getCommitUserData() {
+    throw new UnsupportedOperationException("This reader does not support this method.");
+  }
+
   /**<p>For IndexReader implementations that use
    * TermInfosReader to read terms, this sets the
    * indexDivisor to subsample the number of indexed terms

src/java/org/apache/lucene/index/IndexWriter.java

@@ -3400,8 +3400,16 @@ public class IndexWriter {
     flush(true, false, true);
   }
 
-  /** <p>Expert: prepare for commit.  This does the first
-   *  phase of 2-phase commit.  You can only call this when
+  /** Expert: prepare for commit.
+   * @see #prepareCommit(String) */
+  public final void prepareCommit() throws CorruptIndexException, IOException {
+    ensureOpen();
+    prepareCommit(null);
+  }
+
+  /** <p>Expert: prepare for commit, specifying
+   *  commitUserData String.  This does the first phase of
+   *  2-phase commit.  You can only call this when
    *  autoCommit is false.  This method does all steps
    *  necessary to commit changes since this writer was
    *  opened: flushes pending added and deleted docs, syncs
@@ -3410,17 +3418,28 @@ public class IndexWriter {
    *  #commit()} to finish the commit, or {@link
    *  #rollback()} to revert the commit and undo all changes
    *  done since the writer was opened.</p>
+   * 
+   *  You can also just call {@link #commit(String)} directly
+   *  without prepareCommit first in which case that method
+   *  will internally call prepareCommit.
    *
-   * You can also just call {@link #commit()} directly
-   * without prepareCommit first in which case that method
-   * will internally call prepareCommit.
+   *  @param commitUserData Opaque String that's recorded
+   *  into the segments file in the index, and retrievable
+   *  by {@link IndexReader#getCommitUserData}.  Note that
+   *  when IndexWriter commits itself, for example if open
+   *  with autoCommit=true, or, during {@link #close}, the
+   *  commitUserData is unchanged (just carried over from
+   *  the prior commit).  If this is null then the previous
+   *  commitUserData is kept.  Also, the commitUserData will
+   *  only "stick" if there are actually changes in the
+   *  index to commit.  Therefore it's best to use this
+   *  feature only when autoCommit is false.
    */
-  public final void prepareCommit() throws CorruptIndexException, IOException {
-    ensureOpen();
-    prepareCommit(false);
+  public final void prepareCommit(String commitUserData) throws CorruptIndexException, IOException {
+    prepareCommit(commitUserData, false);
   }
 
-  private final void prepareCommit(boolean internal) throws CorruptIndexException, IOException {
+  private final void prepareCommit(String commitUserData, boolean internal) throws CorruptIndexException, IOException {
 
     if (hitOOM)
       throw new IllegalStateException("this writer hit an OutOfMemoryError; cannot commit");
@@ -3435,11 +3454,11 @@ public class IndexWriter {
 
     flush(true, true, true);
 
-    startCommit(0);
+    startCommit(0, commitUserData);
   }
 
   private void commit(long sizeInBytes) throws IOException {
-    startCommit(sizeInBytes);
+    startCommit(sizeInBytes, null);
     finishCommit();
   }
 
@@ -3482,7 +3501,17 @@ public class IndexWriter {
    * @see #prepareCommit
    */
 
+  /** Commits all changes to the index.
+   *  @see #commit(String) */
   public final void commit() throws CorruptIndexException, IOException {
+    commit(null);
+  }
+
+  /** Commits all changes to the index, specifying a
+   *  commitUserData String.  This just calls {@link
+   *  #prepareCommit(String)} (if you didn't already call
+   *  it) and then {@link #finishCommit}. */
+  public final void commit(String commitUserData) throws CorruptIndexException, IOException {
 
     ensureOpen();
 
@@ -3494,7 +3523,7 @@ public class IndexWriter {
 
       if (autoCommit || pendingCommit == null) {
         message("commit: now prepare");
-        prepareCommit(true);
+        prepareCommit(commitUserData, true);
       } else
         message("commit: already prepared");
 
@@ -3513,6 +3542,7 @@ public class IndexWriter {
         message("commit: wrote segments file \"" + pendingCommit.getCurrentSegmentFileName() + "\"");
         lastCommitChangeCount = pendingCommitChangeCount;
         segmentInfos.updateGeneration(pendingCommit);
+        segmentInfos.setUserData(pendingCommit.getUserData());
         setRollbackSegmentInfos(pendingCommit);
         deleter.checkpoint(pendingCommit, true);
       } finally {
@@ -4600,7 +4630,7 @@ public class IndexWriter {
    *  if it wasn't already.  If that succeeds, then we
    *  prepare a new segments_N file but do not fully commit
    *  it. */
-  private void startCommit(long sizeInBytes) throws IOException {
+  private void startCommit(long sizeInBytes, String commitUserData) throws IOException {
 
     assert testPoint("startStartCommit");
 
@@ -4655,6 +4685,10 @@ public class IndexWriter {
             message("startCommit index=" + segString(segmentInfos) + " changeCount=" + changeCount);
 
           toSync = (SegmentInfos) segmentInfos.clone();
+
+          if (commitUserData != null)
+            toSync.setUserData(commitUserData);
+
           deleter.incRef(toSync, false);
           myChangeCount = changeCount;
         } finally {

src/java/org/apache/lucene/index/SegmentInfos.java

@@ -69,8 +69,11 @@ final class SegmentInfos extends Vector {
    *  omitTf==false) */
   public static final int FORMAT_HAS_PROX = -7;
 
+  /** This format adds optional commit userData (String) storage. */
+  public static final int FORMAT_USER_DATA = -8;
+
   /* This must always point to the most recent file format. */
-  static final int CURRENT_FORMAT = FORMAT_HAS_PROX;
+  static final int CURRENT_FORMAT = FORMAT_USER_DATA;
   
   public int counter = 0;    // used to name new segments
   /**
@@ -84,6 +87,8 @@ final class SegmentInfos extends Vector {
                                    // or wrote; this is normally the same as generation except if
                                    // there was an IOException that had interrupted a commit
 
+  private String userData;                        // Opaque String that user can specify during IndexWriter.commit
+
   /**
    * If non-null, information about loading segments_N files
    * will be printed here.  @see #setInfoStream.
@@ -241,6 +246,13 @@ final class SegmentInfos extends Vector {
           version = input.readLong(); // read version
       }
 
+      if (format <= FORMAT_USER_DATA) {
+        if (0 == input.readByte())
+          userData = null;
+        else
+          userData = input.readString();
+      }
+
       if (format <= FORMAT_CHECKSUM) {
         final long checksumNow = input.getChecksum();
         final long checksumThen = input.readLong();
@@ -306,6 +318,12 @@ final class SegmentInfos extends Vector {
       for (int i = 0; i < size(); i++) {
         info(i).write(output);
       }
+      if (userData == null)
+        output.writeByte((byte) 0);
+      else {
+        output.writeByte((byte) 1);
+        output.writeString(userData);
+      }
       output.prepareCommit();
       success = true;
       pendingOutput = output;
@@ -394,6 +412,18 @@ final class SegmentInfos extends Vector {
       }.run()).longValue();
   }
 
+  /**
+   * Returns userData from latest segments file
+   * @throws CorruptIndexException if the index is corrupt
+   * @throws IOException if there is a low-level IO error
+   */
+  public static String readCurrentUserData(Directory directory)
+    throws CorruptIndexException, IOException {
+    SegmentInfos sis = new SegmentInfos();
+    sis.read(directory);
+    return sis.getUserData();
+  }
+
   /** If non-null, information about retries when loading
    * the segments file will be printed to this.
    */
@@ -841,6 +871,14 @@ final class SegmentInfos extends Vector {
     return buffer.toString();
   }
 
+  public String getUserData() {
+    return userData;
+  }
+
+  public void setUserData(String data) {
+    userData = data;
+  }
+
   /** Replaces all segments in this instance, but keeps
    *  generation, version, counter so that future commits
    *  remain write once.

src/java/org/apache/lucene/index/SnapshotDeletionPolicy.java

@@ -118,6 +118,9 @@ public class SnapshotDeletionPolicy implements IndexDeletionPolicy {
     public long getGeneration() {
       return cp.getGeneration();
     }
+    public String getUserData() throws IOException {
+      return cp.getUserData();
+    }
   }
 
   private List wrapCommits(List commits) {

src/site/src/documentation/content/xdocs/fileformats.xml

@@ -830,6 +830,12 @@
                     NormGen<sup>NumField</sup>,
                     IsCompoundFile, DeletionCount, HasProx&gt;<sup>SegCount</sup>, Checksum
                 </p>
+                <p>
+                    <b>2.9 and above:</b>
+                    Segments --&gt; Format, Version, NameCounter, SegCount, &lt;SegName, SegSize, DelGen, DocStoreOffset, [DocStoreSegment, DocStoreIsCompoundFile], HasSingleNormFile, NumField,
+                    NormGen<sup>NumField</sup>,
+                    IsCompoundFile, DeletionCount, HasProx&gt;<sup>SegCount</sup>, HasUserData, CommitUserData?, Checksum
+                </p>
 
                 <p>
                     Format, NameCounter, SegCount, SegSize, NumField,
@@ -841,16 +847,16 @@
                 </p>
 
                 <p>
-                    SegName, DocStoreSegment --&gt; String
+                    SegName, DocStoreSegment, CommitUserData --&gt; String
                 </p>
 
                 <p>
                     IsCompoundFile, HasSingleNormFile,
-                    DocStoreIsCompoundFile, HasProx --&gt; Int8
+                    DocStoreIsCompoundFile, HasProx, HasUserData --&gt; Int8
                 </p>
 
                 <p>
-                    Format is -1 as of Lucene 1.4, -3 (SegmentInfos.FORMAT_SINGLE_NORM_FILE) as of Lucene 2.1 and 2.2, -4 (SegmentInfos.FORMAT_SHARED_DOC_STORE) as of Lucene 2.3 and -7 (SegmentInfos.FORMAT_HAS_PROX) as of Lucene 2.4.
+                    Format is -1 as of Lucene 1.4, -3 (SegmentInfos.FORMAT_SINGLE_NORM_FILE) as of Lucene 2.1 and 2.2, -4 (SegmentInfos.FORMAT_SHARED_DOC_STORE) as of Lucene 2.3, -7 (SegmentInfos.FORMAT_HAS_PROX) as of Lucene 2.4, and -8 (SegmentInfos.FORMAT_USER_DATA) as of Lucene 2.9.
                 </p>
 
                 <p>
@@ -951,6 +957,13 @@
 		    omitTf set to false; else, it's 0.
 		</p>
 
+		<p>
+		    If HasUserData is 1, then the string
+		    CommitUserData is non-null and is stored.  This is
+		    a string previously passed to IndexWriter's commit
+		    or prepareCommit method.
+                </p>
+
             </section>
 
             <section id="Lock File"><title>Lock File</title>

src/test/org/apache/lucene/index/TestIndexWriter.java

@@ -4116,6 +4116,44 @@ public class TestIndexWriter extends LuceneTestCase
     }
   }
 
+  // LUCENE-1382
+  public void testCommitUserData() throws IOException {
+    Directory dir = new MockRAMDirectory();
+    IndexWriter w = new IndexWriter(dir, new WhitespaceAnalyzer(), IndexWriter.MaxFieldLength.LIMITED);
+    w.setMaxBufferedDocs(2);
+    for(int j=0;j<17;j++)
+      addDoc(w);
+    w.close();
+
+    assertEquals(null, IndexReader.getCommitUserData(dir));
+
+    IndexReader r = IndexReader.open(dir);
+    // commit(String) never called for this index
+    assertEquals(null, r.getCommitUserData());
+    r.close();
+      
+    w = new IndexWriter(dir, new WhitespaceAnalyzer(), IndexWriter.MaxFieldLength.LIMITED);
+    w.setMaxBufferedDocs(2);
+    for(int j=0;j<17;j++)
+      addDoc(w);
+    w.commit("test1");
+    w.close();
+      
+    assertEquals("test1", IndexReader.getCommitUserData(dir));
+
+    r = IndexReader.open(dir);
+    assertEquals("test1", r.getCommitUserData());
+    r.close();
+
+    w = new IndexWriter(dir, new WhitespaceAnalyzer(), IndexWriter.MaxFieldLength.LIMITED);
+    w.optimize();
+    w.close();
+
+    assertEquals("test1", IndexReader.getCommitUserData(dir));
+      
+    dir.close();
+  }
+
   public void testOptimizeExceptions() throws IOException {
     RAMDirectory startDir = new MockRAMDirectory();
     IndexWriter w = new IndexWriter(startDir, new WhitespaceAnalyzer(), IndexWriter.MaxFieldLength.UNLIMITED);