Merge changes Iea17346e,Ifba1d457,I7895e7c1

* changes:
  Move static types out of ChangeRebuilderImpl
  Move ChangeRebuilder(Impl) to a subpackage
  ChangeBundle: Remove infeasible TODO

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/server/notedb/ChangeRebuilderIT.java

@@ -59,10 +59,10 @@ import com.google.gerrit.server.git.RepoRefCache;
 import com.google.gerrit.server.git.UpdateException;
 import com.google.gerrit.server.notedb.ChangeBundle;
 import com.google.gerrit.server.notedb.ChangeNotes;
-import com.google.gerrit.server.notedb.ChangeRebuilder.NoPatchSetsException;
 import com.google.gerrit.server.notedb.NoteDbChangeState;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager;
 import com.google.gerrit.server.notedb.TestChangeRebuilderWrapper;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder.NoPatchSetsException;
 import com.google.gerrit.testutil.ConfigSuite;
 import com.google.gerrit.testutil.NoteDbChecker;
 import com.google.gerrit.testutil.NoteDbMode;

gerrit-pgm/src/main/java/com/google/gerrit/pgm/RebuildNoteDb.java

@@ -47,8 +47,8 @@ import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.WorkQueue;
 import com.google.gerrit.server.index.DummyIndexModule;
 import com.google.gerrit.server.index.change.ReindexAfterUpdate;
-import com.google.gerrit.server.notedb.ChangeRebuilder;
 import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.gwtorm.server.OrmException;
 import com.google.gwtorm.server.SchemaFactory;
 import com.google.inject.Inject;

gerrit-server/src/main/java/com/google/gerrit/server/change/Rebuild.java

@@ -20,8 +20,8 @@ import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestModifyView;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.change.Rebuild.Input;
-import com.google.gerrit.server.notedb.ChangeRebuilder;
 import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java

@@ -27,6 +27,7 @@ import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java

@@ -53,6 +53,7 @@ import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.PatchLineCommentsUtil;
 import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl;
 import com.google.gwtorm.client.Column;
 import com.google.gwtorm.server.OrmException;
 
@@ -241,10 +242,7 @@ public class ChangeBundle {
     checkColumns(Change.Id.class, 1);
 
     checkColumns(Change.class,
-        1, 2, 3, 4, 5, 7, 8, 10, 12, 13, 14, 17, 18,
-        // TODO(dborowitz): It's potentially possible to compare noteDbState in
-        // the Change with the state implied by a ChangeNotes.
-        101);
+        1, 2, 3, 4, 5, 7, 8, 10, 12, 13, 14, 17, 18, 101);
     checkColumns(ChangeMessage.Key.class, 1, 2);
     checkColumns(ChangeMessage.class, 1, 2, 3, 4, 5, 6);
     checkColumns(PatchSet.Id.class, 1, 2);

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNoteUtil.java

@@ -61,20 +61,21 @@ import java.util.Locale;
 import java.util.Set;
 
 public class ChangeNoteUtil {
-  static final FooterKey FOOTER_BRANCH = new FooterKey("Branch");
-  static final FooterKey FOOTER_CHANGE_ID = new FooterKey("Change-id");
-  static final FooterKey FOOTER_COMMIT = new FooterKey("Commit");
-  static final FooterKey FOOTER_GROUPS = new FooterKey("Groups");
-  static final FooterKey FOOTER_HASHTAGS = new FooterKey("Hashtags");
-  static final FooterKey FOOTER_LABEL = new FooterKey("Label");
-  static final FooterKey FOOTER_PATCH_SET = new FooterKey("Patch-set");
-  static final FooterKey FOOTER_STATUS = new FooterKey("Status");
-  static final FooterKey FOOTER_SUBJECT = new FooterKey("Subject");
-  static final FooterKey FOOTER_SUBMISSION_ID = new FooterKey("Submission-id");
-  static final FooterKey FOOTER_SUBMITTED_WITH =
+  public static final FooterKey FOOTER_BRANCH = new FooterKey("Branch");
+  public static final FooterKey FOOTER_CHANGE_ID = new FooterKey("Change-id");
+  public static final FooterKey FOOTER_COMMIT = new FooterKey("Commit");
+  public static final FooterKey FOOTER_GROUPS = new FooterKey("Groups");
+  public static final FooterKey FOOTER_HASHTAGS = new FooterKey("Hashtags");
+  public static final FooterKey FOOTER_LABEL = new FooterKey("Label");
+  public static final FooterKey FOOTER_PATCH_SET = new FooterKey("Patch-set");
+  public static final FooterKey FOOTER_STATUS = new FooterKey("Status");
+  public static final FooterKey FOOTER_SUBJECT = new FooterKey("Subject");
+  public static final FooterKey FOOTER_SUBMISSION_ID =
+      new FooterKey("Submission-id");
+  public static final FooterKey FOOTER_SUBMITTED_WITH =
       new FooterKey("Submitted-with");
-  static final FooterKey FOOTER_TOPIC = new FooterKey("Topic");
-  static final FooterKey FOOTER_TAG = new FooterKey("Tag");
+  public static final FooterKey FOOTER_TOPIC = new FooterKey("Topic");
+  public static final FooterKey FOOTER_TAG = new FooterKey("Tag");
 
   private static final String AUTHOR = "Author";
   private static final String BASE_PATCH_SET = "Base-for-patch-set";

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java

@@ -52,6 +52,7 @@ import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.git.RefCache;
 import com.google.gerrit.server.git.RepoRefCache;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.query.change.ChangeData;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java

@@ -284,7 +284,7 @@ public class ChangeUpdate extends AbstractChangeUpdate {
     this.commitSubject = commitSubject;
   }
 
-  void setSubject(String subject) {
+  public void setSubject(String subject) {
     this.subject = subject;
   }
 

gerrit-server/src/main/java/com/google/gerrit/server/notedb/DraftCommentNotes.java

@@ -31,6 +31,7 @@ import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.git.RepoRefCache;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.StagedResult;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.assistedinject.Assisted;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/NoteDbChangeState.java

@@ -78,7 +78,7 @@ public class NoteDbChangeState {
   }
 
   @VisibleForTesting
-  static NoteDbChangeState parse(Change.Id id, String str) {
+  public static NoteDbChangeState parse(Change.Id id, String str) {
     if (str == null) {
       return null;
     }
@@ -204,7 +204,7 @@ public class NoteDbChangeState {
     return id.get().equals(draftIds.get(accountId));
   }
 
-  boolean isUpToDate(RefCache changeRepoRefs, RefCache draftsRepoRefs)
+  public boolean isUpToDate(RefCache changeRepoRefs, RefCache draftsRepoRefs)
       throws IOException {
     if (!isChangeUpToDate(changeRepoRefs)) {
       return false;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/NoteDbModule.java

@@ -23,6 +23,8 @@ import com.google.gerrit.reviewdb.client.Change.Id;
 import com.google.gerrit.reviewdb.client.Project.NameKey;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.Result;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl;
 import com.google.inject.TypeLiteral;
 import com.google.inject.name.Names;
 

gerrit-server/src/main/java/com/google/gerrit/server/notedb/NoteDbUpdateManager.java

@@ -119,10 +119,10 @@ public class NoteDbUpdateManager implements AutoCloseable {
     @Nullable abstract NoteDbUpdateManager.StagedResult staged();
   }
 
-  static class OpenRepo implements AutoCloseable {
-    final Repository repo;
-    final RevWalk rw;
-    final ChainedReceiveCommands cmds;
+  public static class OpenRepo implements AutoCloseable {
+    public final Repository repo;
+    public final RevWalk rw;
+    public final ChainedReceiveCommands cmds;
 
     private final InMemoryInserter tempIns;
     @Nullable private final ObjectInserter finalIns;
@@ -143,7 +143,7 @@ public class NoteDbUpdateManager implements AutoCloseable {
       this.close = close;
     }
 
-    Optional<ObjectId> getObjectId(String refName) throws IOException {
+    public Optional<ObjectId> getObjectId(String refName) throws IOException {
       return cmds.get(refName);
     }
 
@@ -233,17 +233,17 @@ public class NoteDbUpdateManager implements AutoCloseable {
     return this;
   }
 
-  NoteDbUpdateManager setCheckExpectedState(boolean checkExpectedState) {
+  public NoteDbUpdateManager setCheckExpectedState(boolean checkExpectedState) {
     this.checkExpectedState = checkExpectedState;
     return this;
   }
 
-  OpenRepo getChangeRepo() throws IOException {
+  public OpenRepo getChangeRepo() throws IOException {
     initChangeRepo();
     return changeRepo;
   }
 
-  OpenRepo getAllUsersRepo() throws IOException {
+  public OpenRepo getAllUsersRepo() throws IOException {
     initAllUsersRepo();
     return allUsersRepo;
   }

gerrit-server/src/main/java/com/google/gerrit/server/notedb/TestChangeRebuilderWrapper.java

@@ -20,6 +20,8 @@ import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.Result;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gwtorm.server.OrmException;
 import com.google.gwtorm.server.SchemaFactory;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/AbortUpdateException.java

@@ -0,0 +1,25 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gwtorm.server.OrmRuntimeException;
+
+class AbortUpdateException extends OrmRuntimeException {
+  private static final long serialVersionUID = 1L;
+
+  AbortUpdateException() {
+    super("aborted");
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ApprovalEvent.java

@@ -0,0 +1,41 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+
+import java.sql.Timestamp;
+
+class ApprovalEvent extends Event {
+  private PatchSetApproval psa;
+
+  ApprovalEvent(PatchSetApproval psa, Timestamp changeCreatedOn) {
+    super(psa.getPatchSetId(), psa.getAccountId(), psa.getGranted(),
+        changeCreatedOn, psa.getTag());
+    this.psa = psa;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return false;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) {
+    checkUpdate(update);
+    update.putApproval(psa.getLabel(), psa.getValue());
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ChangeMessageEvent.java

@@ -0,0 +1,106 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.ChangeMessage;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gwtorm.server.OrmException;
+
+import java.sql.Timestamp;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+class ChangeMessageEvent extends Event {
+  private static final Pattern TOPIC_SET_REGEXP =
+      Pattern.compile("^Topic set to (.+)$");
+  private static final Pattern TOPIC_CHANGED_REGEXP =
+      Pattern.compile("^Topic changed from (.+) to (.+)$");
+  private static final Pattern TOPIC_REMOVED_REGEXP =
+      Pattern.compile("^Topic (.+) removed$");
+
+  private static final Pattern STATUS_ABANDONED_REGEXP =
+      Pattern.compile("^Abandoned(\n.*)*$");
+  private static final Pattern STATUS_RESTORED_REGEXP =
+      Pattern.compile("^Restored(\n.*)*$");
+
+  private final ChangeMessage message;
+  private final Change noteDbChange;
+
+  ChangeMessageEvent(ChangeMessage message, Change noteDbChange,
+      Timestamp changeCreatedOn) {
+    super(message.getPatchSetId(), message.getAuthor(),
+        message.getWrittenOn(), changeCreatedOn, message.getTag());
+    this.message = message;
+    this.noteDbChange = noteDbChange;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return true;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws OrmException {
+    checkUpdate(update);
+    update.setChangeMessage(message.getMessage());
+    setTopic(update);
+    setStatus(update);
+  }
+
+  private void setTopic(ChangeUpdate update) {
+    String msg = message.getMessage();
+    if (msg == null) {
+      return;
+    }
+    Matcher m = TOPIC_SET_REGEXP.matcher(msg);
+    if (m.matches()) {
+      String topic = m.group(1);
+      update.setTopic(topic);
+      noteDbChange.setTopic(topic);
+      return;
+    }
+
+    m = TOPIC_CHANGED_REGEXP.matcher(msg);
+    if (m.matches()) {
+      String topic = m.group(2);
+      update.setTopic(topic);
+      noteDbChange.setTopic(topic);
+      return;
+    }
+
+    if (TOPIC_REMOVED_REGEXP.matcher(msg).matches()) {
+      update.setTopic(null);
+      noteDbChange.setTopic(null);
+    }
+  }
+
+  private void setStatus(ChangeUpdate update) {
+    String msg = message.getMessage();
+    if (msg == null) {
+      return;
+    }
+    if (STATUS_ABANDONED_REGEXP.matcher(msg).matches()) {
+      update.setStatus(Change.Status.ABANDONED);
+      noteDbChange.setStatus(Change.Status.ABANDONED);
+      return;
+    }
+
+    if (STATUS_RESTORED_REGEXP.matcher(msg).matches()) {
+      update.setStatus(Change.Status.NEW);
+      noteDbChange.setStatus(Change.Status.NEW);
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ChangeRebuilder.java

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package com.google.gerrit.server.notedb;
+package com.google.gerrit.server.notedb.rebuild;
 
 import com.google.common.collect.ImmutableMultimap;
 import com.google.common.util.concurrent.ListenableFuture;
@@ -20,6 +20,8 @@ import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.notedb.ChangeBundle;
+import com.google.gerrit.server.notedb.NoteDbUpdateManager;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.Result;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gwtorm.server.OrmException;

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ChangeRebuilderImpl.java

@@ -12,19 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package com.google.gerrit.server.notedb;
+package com.google.gerrit.server.notedb.rebuild;
 
 import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.gerrit.reviewdb.client.RefNames.changeMetaRef;
-import static com.google.gerrit.server.PatchLineCommentsUtil.setCommentRevId;
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_HASHTAGS;
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_PATCH_SET;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
-import com.google.common.base.MoreObjects;
 import com.google.common.base.Optional;
 import com.google.common.base.Predicate;
 import com.google.common.base.Splitter;
@@ -56,20 +53,25 @@ import com.google.gerrit.server.PatchLineCommentsUtil;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.config.AnonymousCowardName;
 import com.google.gerrit.server.git.ChainedReceiveCommands;
+import com.google.gerrit.server.notedb.ChangeBundle;
+import com.google.gerrit.server.notedb.ChangeDraftUpdate;
+import com.google.gerrit.server.notedb.ChangeNoteUtil;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.notedb.NoteDbChangeState;
+import com.google.gerrit.server.notedb.NoteDbUpdateManager;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.OpenRepo;
 import com.google.gerrit.server.notedb.NoteDbUpdateManager.Result;
+import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gwtorm.server.AtomicUpdate;
 import com.google.gwtorm.server.OrmException;
-import com.google.gwtorm.server.OrmRuntimeException;
 import com.google.gwtorm.server.SchemaFactory;
 import com.google.inject.Inject;
 
 import org.eclipse.jgit.errors.ConfigInvalidException;
-import org.eclipse.jgit.errors.InvalidObjectIdException;
-import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.PersonIdent;
@@ -92,8 +94,6 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 public class ChangeRebuilderImpl extends ChangeRebuilder {
   private static final Logger log =
@@ -108,13 +108,13 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
    * historically didn't necessarily use the same timestamp, and tended to call
    * {@code System.currentTimeMillis()} independently.
    */
-  static final long MAX_WINDOW_MS = SECONDS.toMillis(3);
+  public static final long MAX_WINDOW_MS = SECONDS.toMillis(3);
 
   /**
    * The maximum amount of time between two consecutive events to consider them
    * to be in the same batch.
    */
-  private static final long MAX_DELTA_MS = SECONDS.toMillis(1);
+  static final long MAX_DELTA_MS = SECONDS.toMillis(1);
 
   private final AccountCache accountCache;
   private final ChangeDraftUpdate.Factory draftUpdateFactory;
@@ -168,24 +168,6 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
     }
   }
 
-  private static class AbortUpdateException extends OrmRuntimeException {
-    private static final long serialVersionUID = 1L;
-
-    AbortUpdateException() {
-      super("aborted");
-    }
-  }
-
-  private static class ConflictingUpdateException extends OrmRuntimeException {
-    private static final long serialVersionUID = 1L;
-
-    ConflictingUpdateException(Change change, String expectedNoteDbState) {
-      super(String.format(
-          "Expected change %s to have noteDbState %s but was %s",
-          change.getId(), expectedNoteDbState, change.getNoteDbState()));
-    }
-  }
-
   @Override
   public Result rebuild(NoteDbUpdateManager manager,
       ChangeBundle bundle) throws NoSuchChangeException, IOException,
@@ -466,7 +448,7 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
     ChangeUpdate update = updateFactory.create(
         change,
         events.getAccountId(),
-        events.newAuthorIdent(),
+        newAuthorIdent(events),
         events.getWhen(),
         labelNameComparator);
     update.setAllowWriteToNewRef(true);
@@ -488,7 +470,7 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
     ChangeDraftUpdate update = draftUpdateFactory.create(
         change,
         events.getAccountId(),
-        events.newAuthorIdent(),
+        newAuthorIdent(events),
         events.getWhen());
     update.setPatchSetId(events.getPatchSetId());
     for (PatchLineCommentEvent e : events) {
@@ -498,6 +480,16 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
     events.clear();
   }
 
+  private PersonIdent newAuthorIdent(EventList<?> events) {
+    Account.Id id = events.getAccountId();
+    if (id == null) {
+      return new PersonIdent(serverIdent, events.getWhen());
+    }
+    return changeNoteUtil.newIdent(
+        accountCache.get(id).getAccount(), events.getWhen(), serverIdent,
+        anonymousCowardName);
+  }
+
   private List<HashtagsEvent> getHashtagsEvents(Change change,
       NoteDbUpdateManager manager) throws IOException {
     String refName = changeMetaRef(change.getId());
@@ -591,470 +583,10 @@ public class ChangeRebuilderImpl extends ChangeRebuilder {
     }
   };
 
-  private abstract static class Event {
-    // NOTE: EventList only supports direct subclasses, not an arbitrary
-    // hierarchy.
-
-    final Account.Id who;
-    final Timestamp when;
-    final String tag;
-    final boolean predatesChange;
-    PatchSet.Id psId;
-
-    protected Event(PatchSet.Id psId, Account.Id who, Timestamp when,
-        Timestamp changeCreatedOn, String tag) {
-      this.psId = psId;
-      this.who = who;
-      this.tag = tag;
-      // Truncate timestamps at the change's createdOn timestamp.
-      predatesChange = when.before(changeCreatedOn);
-      this.when = predatesChange ? changeCreatedOn : when;
-    }
-
-    protected void checkUpdate(AbstractChangeUpdate update) {
-      checkState(Objects.equals(update.getPatchSetId(), psId),
-          "cannot apply event for %s to update for %s",
-          update.getPatchSetId(), psId);
-      checkState(when.getTime() - update.getWhen().getTime() <= MAX_WINDOW_MS,
-          "event at %s outside update window starting at %s",
-          when, update.getWhen());
-      checkState(Objects.equals(update.getNullableAccountId(), who),
-          "cannot apply event by %s to update by %s",
-          who, update.getNullableAccountId());
-    }
-
-    /**
-     * @return whether this event type must be unique per {@link ChangeUpdate},
-     *     i.e. there may be at most one of this type.
-     */
-    abstract boolean uniquePerUpdate();
-
-    abstract void apply(ChangeUpdate update) throws OrmException, IOException;
-
-    @Override
-    public String toString() {
-      return MoreObjects.toStringHelper(this)
-          .add("psId", psId)
-          .add("who", who)
-          .add("when", when)
-          .toString();
-    }
-  }
-
-  private class EventList<E extends Event> extends ArrayList<E> {
-    private static final long serialVersionUID = 1L;
-
-    private E getLast() {
-      return get(size() - 1);
-    }
-
-    private long getLastTime() {
-      return getLast().when.getTime();
-    }
-
-    private long getFirstTime() {
-      return get(0).when.getTime();
-    }
-
-    boolean canAdd(E e) {
-      if (isEmpty()) {
-        return true;
-      }
-      if (e instanceof FinalUpdatesEvent) {
-        return false; // FinalUpdatesEvent always gets its own update.
-      }
-
-      Event last = getLast();
-      if (!Objects.equals(e.who, last.who)
-          || !e.psId.equals(last.psId)
-          || !Objects.equals(e.tag, last.tag)) {
-        return false; // Different patch set, author, or tag.
-      }
-
-      long t = e.when.getTime();
-      long tFirst = getFirstTime();
-      long tLast = getLastTime();
-      checkArgument(t >= tLast,
-          "event %s is before previous event in list %s", e, last);
-      if (t - tLast > MAX_DELTA_MS || t - tFirst > MAX_WINDOW_MS) {
-        return false; // Too much time elapsed.
-      }
-
-      if (!e.uniquePerUpdate()) {
-        return true;
-      }
-      for (Event o : this) {
-        if (e.getClass() == o.getClass()) {
-          return false; // Only one event of this type allowed per update.
-        }
-      }
-
-      // TODO(dborowitz): Additional heuristics, like keeping events separate if
-      // they affect overlapping fields within a single entity.
-
-      return true;
-    }
-
-    Timestamp getWhen() {
-      return get(0).when;
-    }
-
-    PatchSet.Id getPatchSetId() {
-      PatchSet.Id id = checkNotNull(get(0).psId);
-      for (int i = 1; i < size(); i++) {
-        checkState(get(i).psId.equals(id),
-            "mismatched patch sets in EventList: %s != %s", id, get(i).psId);
-      }
-      return id;
-    }
-
-    Account.Id getAccountId() {
-      Account.Id id = get(0).who;
-      for (int i = 1; i < size(); i++) {
-        checkState(Objects.equals(id, get(i).who),
-            "mismatched users in EventList: %s != %s", id, get(i).who);
-      }
-      return id;
-    }
-
-    PersonIdent newAuthorIdent() {
-      Account.Id id = getAccountId();
-      if (id == null) {
-        return new PersonIdent(serverIdent, getWhen());
-      }
-      return changeNoteUtil.newIdent(
-          accountCache.get(id).getAccount(), getWhen(), serverIdent,
-          anonymousCowardName);
-    }
-
-    String getTag() {
-      return getLast().tag;
-    }
-  }
-
-  private static void createChange(ChangeUpdate update, Change change) {
+  static void createChange(ChangeUpdate update, Change change) {
     update.setSubjectForCommit("Create change");
     update.setChangeId(change.getKey().get());
     update.setBranch(change.getDest().get());
     update.setSubject(change.getOriginalSubject());
   }
-
-  private static class CreateChangeEvent extends Event {
-    private final Change change;
-
-    private static PatchSet.Id psId(Change change, Integer minPsNum) {
-      int n;
-      if (minPsNum == null) {
-        // There were no patch sets for the change at all, so something is very
-        // wrong. Bail and use 1 as the patch set.
-        n = 1;
-      } else {
-        n = minPsNum;
-      }
-      return new PatchSet.Id(change.getId(), n);
-    }
-
-    CreateChangeEvent(Change change, Integer minPsNum) {
-      super(psId(change, minPsNum), change.getOwner(), change.getCreatedOn(),
-          change.getCreatedOn(), null);
-      this.change = change;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return true;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws IOException, OrmException {
-      checkUpdate(update);
-      createChange(update, change);
-    }
-  }
-
-  private static class ApprovalEvent extends Event {
-    private PatchSetApproval psa;
-
-    ApprovalEvent(PatchSetApproval psa, Timestamp changeCreatedOn) {
-      super(psa.getPatchSetId(), psa.getAccountId(), psa.getGranted(),
-          changeCreatedOn, psa.getTag());
-      this.psa = psa;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return false;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) {
-      checkUpdate(update);
-      update.putApproval(psa.getLabel(), psa.getValue());
-    }
-  }
-
-  private static class ReviewerEvent extends Event {
-    private Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> reviewer;
-
-    ReviewerEvent(
-        Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> reviewer,
-        Timestamp changeCreatedOn) {
-      super(
-          // Reviewers aren't generally associated with a particular patch set
-          // (although as an implementation detail they were in ReviewDb). Just
-          // use the latest patch set at the time of the event.
-          null,
-          reviewer.getColumnKey(), reviewer.getValue(), changeCreatedOn, null);
-      this.reviewer = reviewer;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return false;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws IOException, OrmException {
-      checkUpdate(update);
-      update.putReviewer(reviewer.getColumnKey(), reviewer.getRowKey());
-    }
-  }
-
-  private static class PatchSetEvent extends Event {
-    private final Change change;
-    private final PatchSet ps;
-    private final RevWalk rw;
-    private boolean createChange;
-
-    PatchSetEvent(Change change, PatchSet ps, RevWalk rw) {
-      super(ps.getId(), ps.getUploader(), ps.getCreatedOn(),
-          change.getCreatedOn(), null);
-      this.change = change;
-      this.ps = ps;
-      this.rw = rw;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return true;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws IOException, OrmException {
-      checkUpdate(update);
-      if (createChange) {
-        createChange(update, change);
-      } else {
-        update.setSubject(change.getSubject());
-        update.setSubjectForCommit("Create patch set " + ps.getPatchSetId());
-      }
-      setRevision(update, ps);
-      List<String> groups = ps.getGroups();
-      if (!groups.isEmpty()) {
-        update.setGroups(ps.getGroups());
-      }
-      if (ps.isDraft()) {
-        update.setPatchSetState(PatchSetState.DRAFT);
-      }
-    }
-
-    private void setRevision(ChangeUpdate update, PatchSet ps)
-        throws IOException {
-      String rev = ps.getRevision().get();
-      String cert = ps.getPushCertificate();
-      ObjectId id;
-      try {
-        id = ObjectId.fromString(rev);
-      } catch (InvalidObjectIdException e) {
-        update.setRevisionForMissingCommit(rev, cert);
-        return;
-      }
-      try {
-        update.setCommit(rw, id, cert);
-      } catch (MissingObjectException e) {
-        update.setRevisionForMissingCommit(rev, cert);
-        return;
-      }
-    }
-  }
-
-  private static class PatchLineCommentEvent extends Event {
-    public final PatchLineComment c;
-    private final Change change;
-    private final PatchSet ps;
-    private final PatchListCache cache;
-
-    PatchLineCommentEvent(PatchLineComment c, Change change, PatchSet ps,
-        PatchListCache cache) {
-      super(PatchLineCommentsUtil.getCommentPsId(c), c.getAuthor(),
-          c.getWrittenOn(), change.getCreatedOn(), c.getTag());
-      this.c = c;
-      this.change = change;
-      this.ps = ps;
-      this.cache = cache;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return false;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws OrmException {
-      checkUpdate(update);
-      if (c.getRevId() == null) {
-        setCommentRevId(c, cache, change, ps);
-      }
-      update.putComment(c);
-    }
-
-    void applyDraft(ChangeDraftUpdate draftUpdate) throws OrmException {
-      if (c.getRevId() == null) {
-        setCommentRevId(c, cache, change, ps);
-      }
-      draftUpdate.putComment(c);
-    }
-  }
-
-  private static class HashtagsEvent extends Event {
-    private final Set<String> hashtags;
-
-    HashtagsEvent(PatchSet.Id psId, Account.Id who, Timestamp when,
-        Set<String> hashtags, Timestamp changeCreatdOn) {
-      super(psId, who, when, changeCreatdOn,
-          // Somewhat confusingly, hashtags do not use the setTag method on
-          // AbstractChangeUpdate, so pass null as the tag.
-          null);
-      this.hashtags = hashtags;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      // Since these are produced from existing commits in the old NoteDb graph,
-      // we know that there must be one per commit in the rebuilt graph.
-      return true;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws OrmException {
-      update.setHashtags(hashtags);
-    }
-  }
-
-  private static class ChangeMessageEvent extends Event {
-    private static final Pattern TOPIC_SET_REGEXP =
-        Pattern.compile("^Topic set to (.+)$");
-    private static final Pattern TOPIC_CHANGED_REGEXP =
-        Pattern.compile("^Topic changed from (.+) to (.+)$");
-    private static final Pattern TOPIC_REMOVED_REGEXP =
-        Pattern.compile("^Topic (.+) removed$");
-
-    private static final Pattern STATUS_ABANDONED_REGEXP =
-        Pattern.compile("^Abandoned(\n.*)*$");
-    private static final Pattern STATUS_RESTORED_REGEXP =
-        Pattern.compile("^Restored(\n.*)*$");
-
-    private final ChangeMessage message;
-    private final Change noteDbChange;
-
-    ChangeMessageEvent(ChangeMessage message, Change noteDbChange,
-        Timestamp changeCreatedOn) {
-      super(message.getPatchSetId(), message.getAuthor(),
-          message.getWrittenOn(), changeCreatedOn, message.getTag());
-      this.message = message;
-      this.noteDbChange = noteDbChange;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return true;
-    }
-
-    @Override
-    void apply(ChangeUpdate update) throws OrmException {
-      checkUpdate(update);
-      update.setChangeMessage(message.getMessage());
-      setTopic(update);
-      setStatus(update);
-    }
-
-    private void setTopic(ChangeUpdate update) {
-      String msg = message.getMessage();
-      if (msg == null) {
-        return;
-      }
-      Matcher m = TOPIC_SET_REGEXP.matcher(msg);
-      if (m.matches()) {
-        String topic = m.group(1);
-        update.setTopic(topic);
-        noteDbChange.setTopic(topic);
-        return;
-      }
-
-      m = TOPIC_CHANGED_REGEXP.matcher(msg);
-      if (m.matches()) {
-        String topic = m.group(2);
-        update.setTopic(topic);
-        noteDbChange.setTopic(topic);
-        return;
-      }
-
-      if (TOPIC_REMOVED_REGEXP.matcher(msg).matches()) {
-        update.setTopic(null);
-        noteDbChange.setTopic(null);
-      }
-    }
-
-    private void setStatus(ChangeUpdate update) {
-      String msg = message.getMessage();
-      if (msg == null) {
-        return;
-      }
-      if (STATUS_ABANDONED_REGEXP.matcher(msg).matches()) {
-        update.setStatus(Change.Status.ABANDONED);
-        noteDbChange.setStatus(Change.Status.ABANDONED);
-        return;
-      }
-
-      if (STATUS_RESTORED_REGEXP.matcher(msg).matches()) {
-        update.setStatus(Change.Status.NEW);
-        noteDbChange.setStatus(Change.Status.NEW);
-      }
-    }
-  }
-
-  private static class FinalUpdatesEvent extends Event {
-    private final Change change;
-    private final Change noteDbChange;
-
-    FinalUpdatesEvent(Change change, Change noteDbChange) {
-      super(change.currentPatchSetId(), change.getOwner(),
-          change.getLastUpdatedOn(), change.getCreatedOn(), null);
-      this.change = change;
-      this.noteDbChange = noteDbChange;
-    }
-
-    @Override
-    boolean uniquePerUpdate() {
-      return true;
-    }
-
-    @SuppressWarnings("deprecation")
-    @Override
-    void apply(ChangeUpdate update) throws OrmException {
-      if (!Objects.equals(change.getTopic(), noteDbChange.getTopic())) {
-        update.setTopic(change.getTopic());
-      }
-      if (!Objects.equals(change.getStatus(), noteDbChange.getStatus())) {
-        // TODO(dborowitz): Stamp approximate approvals at this time.
-        update.fixStatus(change.getStatus());
-      }
-      if (change.getSubmissionId() != null) {
-        update.setSubmissionId(change.getSubmissionId());
-      }
-      if (!update.isEmpty()) {
-        update.setSubjectForCommit("Final NoteDb migration updates");
-      }
-    }
-  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ConflictingUpdateException.java

@@ -0,0 +1,28 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gwtorm.server.OrmRuntimeException;
+
+class ConflictingUpdateException extends OrmRuntimeException {
+  private static final long serialVersionUID = 1L;
+
+  ConflictingUpdateException(Change change, String expectedNoteDbState) {
+    super(String.format(
+        "Expected change %s to have noteDbState %s but was %s",
+        change.getId(), expectedNoteDbState, change.getNoteDbState()));
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/CreateChangeEvent.java

@@ -0,0 +1,55 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gwtorm.server.OrmException;
+
+import java.io.IOException;
+
+class CreateChangeEvent extends Event {
+  private final Change change;
+
+  private static PatchSet.Id psId(Change change, Integer minPsNum) {
+    int n;
+    if (minPsNum == null) {
+      // There were no patch sets for the change at all, so something is very
+      // wrong. Bail and use 1 as the patch set.
+      n = 1;
+    } else {
+      n = minPsNum;
+    }
+    return new PatchSet.Id(change.getId(), n);
+  }
+
+  CreateChangeEvent(Change change, Integer minPsNum) {
+    super(psId(change, minPsNum), change.getOwner(), change.getCreatedOn(),
+        change.getCreatedOn(), null);
+    this.change = change;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return true;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws IOException, OrmException {
+    checkUpdate(update);
+    ChangeRebuilderImpl.createChange(update, change);
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/Event.java

@@ -0,0 +1,79 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl.MAX_WINDOW_MS;
+
+import com.google.common.base.MoreObjects;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.notedb.AbstractChangeUpdate;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gwtorm.server.OrmException;
+
+import java.io.IOException;
+import java.sql.Timestamp;
+import java.util.Objects;
+
+abstract class Event {
+  // NOTE: EventList only supports direct subclasses, not an arbitrary
+  // hierarchy.
+
+  final Account.Id who;
+  final Timestamp when;
+  final String tag;
+  final boolean predatesChange;
+  PatchSet.Id psId;
+
+  protected Event(PatchSet.Id psId, Account.Id who, Timestamp when,
+      Timestamp changeCreatedOn, String tag) {
+    this.psId = psId;
+    this.who = who;
+    this.tag = tag;
+    // Truncate timestamps at the change's createdOn timestamp.
+    predatesChange = when.before(changeCreatedOn);
+    this.when = predatesChange ? changeCreatedOn : when;
+  }
+
+  protected void checkUpdate(AbstractChangeUpdate update) {
+    checkState(Objects.equals(update.getPatchSetId(), psId),
+        "cannot apply event for %s to update for %s",
+        update.getPatchSetId(), psId);
+    checkState(when.getTime() - update.getWhen().getTime() <= MAX_WINDOW_MS,
+        "event at %s outside update window starting at %s",
+        when, update.getWhen());
+    checkState(Objects.equals(update.getNullableAccountId(), who),
+        "cannot apply event by %s to update by %s",
+        who, update.getNullableAccountId());
+  }
+
+  /**
+   * @return whether this event type must be unique per {@link ChangeUpdate},
+   *     i.e. there may be at most one of this type.
+   */
+  abstract boolean uniquePerUpdate();
+
+  abstract void apply(ChangeUpdate update) throws OrmException, IOException;
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("psId", psId)
+        .add("who", who)
+        .add("when", when)
+        .toString();
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/EventList.java

@@ -0,0 +1,107 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSet;
+
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.Objects;
+
+class EventList<E extends Event> extends ArrayList<E> {
+  private static final long serialVersionUID = 1L;
+
+  private E getLast() {
+    return get(size() - 1);
+  }
+
+  private long getLastTime() {
+    return getLast().when.getTime();
+  }
+
+  private long getFirstTime() {
+    return get(0).when.getTime();
+  }
+
+  boolean canAdd(E e) {
+    if (isEmpty()) {
+      return true;
+    }
+    if (e instanceof FinalUpdatesEvent) {
+      return false; // FinalUpdatesEvent always gets its own update.
+    }
+
+    Event last = getLast();
+    if (!Objects.equals(e.who, last.who)
+        || !e.psId.equals(last.psId)
+        || !Objects.equals(e.tag, last.tag)) {
+      return false; // Different patch set, author, or tag.
+    }
+
+    long t = e.when.getTime();
+    long tFirst = getFirstTime();
+    long tLast = getLastTime();
+    checkArgument(t >= tLast,
+        "event %s is before previous event in list %s", e, last);
+    if (t - tLast > ChangeRebuilderImpl.MAX_DELTA_MS || t - tFirst > ChangeRebuilderImpl.MAX_WINDOW_MS) {
+      return false; // Too much time elapsed.
+    }
+
+    if (!e.uniquePerUpdate()) {
+      return true;
+    }
+    for (Event o : this) {
+      if (e.getClass() == o.getClass()) {
+        return false; // Only one event of this type allowed per update.
+      }
+    }
+
+    // TODO(dborowitz): Additional heuristics, like keeping events separate if
+    // they affect overlapping fields within a single entity.
+
+    return true;
+  }
+
+  Timestamp getWhen() {
+    return get(0).when;
+  }
+
+  PatchSet.Id getPatchSetId() {
+    PatchSet.Id id = checkNotNull(get(0).psId);
+    for (int i = 1; i < size(); i++) {
+      checkState(get(i).psId.equals(id),
+          "mismatched patch sets in EventList: %s != %s", id, get(i).psId);
+    }
+    return id;
+  }
+
+  Account.Id getAccountId() {
+    Account.Id id = get(0).who;
+    for (int i = 1; i < size(); i++) {
+      checkState(Objects.equals(id, get(i).who),
+          "mismatched users in EventList: %s != %s", id, get(i).who);
+    }
+    return id;
+  }
+
+  String getTag() {
+    return getLast().tag;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/FinalUpdatesEvent.java

@@ -0,0 +1,56 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gwtorm.server.OrmException;
+
+import java.util.Objects;
+
+class FinalUpdatesEvent extends Event {
+  private final Change change;
+  private final Change noteDbChange;
+
+  FinalUpdatesEvent(Change change, Change noteDbChange) {
+    super(change.currentPatchSetId(), change.getOwner(),
+        change.getLastUpdatedOn(), change.getCreatedOn(), null);
+    this.change = change;
+    this.noteDbChange = noteDbChange;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return true;
+  }
+
+  @SuppressWarnings("deprecation")
+  @Override
+  void apply(ChangeUpdate update) throws OrmException {
+    if (!Objects.equals(change.getTopic(), noteDbChange.getTopic())) {
+      update.setTopic(change.getTopic());
+    }
+    if (!Objects.equals(change.getStatus(), noteDbChange.getStatus())) {
+      // TODO(dborowitz): Stamp approximate approvals at this time.
+      update.fixStatus(change.getStatus());
+    }
+    if (change.getSubmissionId() != null) {
+      update.setSubmissionId(change.getSubmissionId());
+    }
+    if (!update.isEmpty()) {
+      update.setSubjectForCommit("Final NoteDb migration updates");
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/HashtagsEvent.java

@@ -0,0 +1,48 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gwtorm.server.OrmException;
+
+import java.sql.Timestamp;
+import java.util.Set;
+
+class HashtagsEvent extends Event {
+  private final Set<String> hashtags;
+
+  HashtagsEvent(PatchSet.Id psId, Account.Id who, Timestamp when,
+      Set<String> hashtags, Timestamp changeCreatdOn) {
+    super(psId, who, when, changeCreatdOn,
+        // Somewhat confusingly, hashtags do not use the setTag method on
+        // AbstractChangeUpdate, so pass null as the tag.
+        null);
+    this.hashtags = hashtags;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    // Since these are produced from existing commits in the old NoteDb graph,
+    // we know that there must be one per commit in the rebuilt graph.
+    return true;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws OrmException {
+    update.setHashtags(hashtags);
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/PatchLineCommentEvent.java

@@ -0,0 +1,64 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import static com.google.gerrit.server.PatchLineCommentsUtil.setCommentRevId;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.PatchLineComment;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.PatchLineCommentsUtil;
+import com.google.gerrit.server.notedb.ChangeDraftUpdate;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.patch.PatchListCache;
+import com.google.gwtorm.server.OrmException;
+
+class PatchLineCommentEvent extends Event {
+  public final PatchLineComment c;
+  private final Change change;
+  private final PatchSet ps;
+  private final PatchListCache cache;
+
+  PatchLineCommentEvent(PatchLineComment c, Change change, PatchSet ps,
+      PatchListCache cache) {
+    super(PatchLineCommentsUtil.getCommentPsId(c), c.getAuthor(),
+        c.getWrittenOn(), change.getCreatedOn(), c.getTag());
+    this.c = c;
+    this.change = change;
+    this.ps = ps;
+    this.cache = cache;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return false;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws OrmException {
+    checkUpdate(update);
+    if (c.getRevId() == null) {
+      setCommentRevId(c, cache, change, ps);
+    }
+    update.putComment(c);
+  }
+
+  void applyDraft(ChangeDraftUpdate draftUpdate) throws OrmException {
+    if (c.getRevId() == null) {
+      setCommentRevId(c, cache, change, ps);
+    }
+    draftUpdate.putComment(c);
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/PatchSetEvent.java

@@ -0,0 +1,87 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.notedb.PatchSetState;
+import com.google.gwtorm.server.OrmException;
+
+import org.eclipse.jgit.errors.InvalidObjectIdException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.revwalk.RevWalk;
+
+import java.io.IOException;
+import java.util.List;
+
+class PatchSetEvent extends Event {
+  private final Change change;
+  private final PatchSet ps;
+  private final RevWalk rw;
+  boolean createChange;
+
+  PatchSetEvent(Change change, PatchSet ps, RevWalk rw) {
+    super(ps.getId(), ps.getUploader(), ps.getCreatedOn(),
+        change.getCreatedOn(), null);
+    this.change = change;
+    this.ps = ps;
+    this.rw = rw;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return true;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws IOException, OrmException {
+    checkUpdate(update);
+    if (createChange) {
+      ChangeRebuilderImpl.createChange(update, change);
+    } else {
+      update.setSubject(change.getSubject());
+      update.setSubjectForCommit("Create patch set " + ps.getPatchSetId());
+    }
+    setRevision(update, ps);
+    List<String> groups = ps.getGroups();
+    if (!groups.isEmpty()) {
+      update.setGroups(ps.getGroups());
+    }
+    if (ps.isDraft()) {
+      update.setPatchSetState(PatchSetState.DRAFT);
+    }
+  }
+
+  private void setRevision(ChangeUpdate update, PatchSet ps)
+      throws IOException {
+    String rev = ps.getRevision().get();
+    String cert = ps.getPushCertificate();
+    ObjectId id;
+    try {
+      id = ObjectId.fromString(rev);
+    } catch (InvalidObjectIdException e) {
+      update.setRevisionForMissingCommit(rev, cert);
+      return;
+    }
+    try {
+      update.setCommit(rw, id, cert);
+    } catch (MissingObjectException e) {
+      update.setRevisionForMissingCommit(rev, cert);
+      return;
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/notedb/rebuild/ReviewerEvent.java

@@ -0,0 +1,51 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed 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 com.google.gerrit.server.notedb.rebuild;
+
+import com.google.common.collect.Table;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
+import com.google.gwtorm.server.OrmException;
+
+import java.io.IOException;
+import java.sql.Timestamp;
+
+class ReviewerEvent extends Event {
+  private Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> reviewer;
+
+  ReviewerEvent(
+      Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> reviewer,
+      Timestamp changeCreatedOn) {
+    super(
+        // Reviewers aren't generally associated with a particular patch set
+        // (although as an implementation detail they were in ReviewDb). Just
+        // use the latest patch set at the time of the event.
+        null,
+        reviewer.getColumnKey(), reviewer.getValue(), changeCreatedOn, null);
+    this.reviewer = reviewer;
+  }
+
+  @Override
+  boolean uniquePerUpdate() {
+    return false;
+  }
+
+  @Override
+  void apply(ChangeUpdate update) throws IOException, OrmException {
+    checkUpdate(update);
+    update.putReviewer(reviewer.getColumnKey(), reviewer.getRowKey());
+  }
+}

gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeBundleTest.java

@@ -39,6 +39,7 @@ import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl;
 import com.google.gerrit.testutil.TestChanges;
 import com.google.gerrit.testutil.TestTimeUtil;
 import com.google.gwtorm.client.KeyUtil;

gerrit-server/src/test/java/com/google/gerrit/testutil/NoteDbChecker.java

@@ -27,7 +27,7 @@ import com.google.gerrit.server.PatchLineCommentsUtil;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.notedb.ChangeBundle;
 import com.google.gerrit.server.notedb.ChangeNotes;
-import com.google.gerrit.server.notedb.ChangeRebuilder;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilder;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;