diff --git a/gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java b/gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
index 84e7557..f2c701b 100644
--- a/gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
+++ b/gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
@@ -298,7 +298,7 @@
         throws OrmException, NoSuchChangeException {
       Iterable<Account.Id> actualIds = approvalsUtil
           .getReviewers(db, notesFactory.createChecked(db, c))
-          .values();
+          .all();
       assertThat(actualIds).containsExactlyElementsIn(
           Sets.newHashSet(TestAccount.ids(expectedReviewers)));
     }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
index dc3a6b1..847d559 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java
@@ -14,8 +14,6 @@
 
 package com.google.gerrit.server;
 
-import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -23,13 +21,10 @@
 import com.google.common.base.Predicate;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
-import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.Iterables;
-import com.google.common.collect.LinkedHashMultimap;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Ordering;
-import com.google.common.collect.SetMultimap;
 import com.google.common.collect.Sets;
 import com.google.gerrit.common.data.LabelType;
 import com.google.gerrit.common.data.LabelTypes;
@@ -45,7 +40,6 @@
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ChangeUpdate;
 import com.google.gerrit.server.notedb.NotesMigration;
-import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.util.LabelVote;
 import com.google.gwtorm.server.OrmException;
@@ -115,15 +109,14 @@
    *
    * @param db review database.
    * @param notes change notes.
-   * @return multimap of reviewers keyed by state, where each account appears
-   *     exactly once in {@link SetMultimap#values()}, and
-   *     {@link ReviewerStateInternal#REMOVED} is not present.
+   * @return reviewers for the change.
    * @throws OrmException if reviewers for the change could not be read.
    */
-  public ImmutableSetMultimap<ReviewerStateInternal, Account.Id> getReviewers(
-      ReviewDb db, ChangeNotes notes) throws OrmException {
+  public ReviewerSet getReviewers(ReviewDb db, ChangeNotes notes)
+      throws OrmException {
     if (!migration.readChanges()) {
-      return getReviewers(db.patchSetApprovals().byChange(notes.getChangeId()));
+      return ReviewerSet.fromApprovals(
+          db.patchSetApprovals().byChange(notes.getChangeId()));
     }
     return notes.load().getReviewers();
   }
@@ -133,44 +126,18 @@
    *
    * @param allApprovals all approvals to consider; must all belong to the same
    *     change.
-   * @return multimap of reviewers keyed by state, where each account appears
-   *     exactly once in {@link SetMultimap#values()}, and
-   *     {@link ReviewerStateInternal#REMOVED} is not present.
+   * @return reviewers for the change.
+   * @throws OrmException if reviewers for the change could not be read.
    */
-  public ImmutableSetMultimap<ReviewerStateInternal, Account.Id> getReviewers(
-      ChangeNotes notes, Iterable<PatchSetApproval> allApprovals)
+  public ReviewerSet getReviewers(ChangeNotes notes,
+      Iterable<PatchSetApproval> allApprovals)
       throws OrmException {
     if (!migration.readChanges()) {
-      return getReviewers(allApprovals);
+      return ReviewerSet.fromApprovals(allApprovals);
     }
     return notes.load().getReviewers();
   }
 
-  private static ImmutableSetMultimap<ReviewerStateInternal, Account.Id> getReviewers(
-      Iterable<PatchSetApproval> allApprovals) {
-    PatchSetApproval first = null;
-    SetMultimap<ReviewerStateInternal, Account.Id> reviewers =
-        LinkedHashMultimap.create();
-    for (PatchSetApproval psa : allApprovals) {
-      if (first == null) {
-        first = psa;
-      } else {
-        checkArgument(
-            first.getKey().getParentKey().getParentKey().equals(
-              psa.getKey().getParentKey().getParentKey()),
-            "multiple change IDs: %s, %s", first.getKey(), psa.getKey());
-      }
-      Account.Id id = psa.getAccountId();
-      if (psa.getValue() != 0) {
-        reviewers.put(REVIEWER, id);
-        reviewers.remove(CC, id);
-      } else if (!reviewers.containsEntry(REVIEWER, id)) {
-        reviewers.put(CC, id);
-      }
-    }
-    return ImmutableSetMultimap.copyOf(reviewers);
-  }
-
   public List<PatchSetApproval> addReviewers(ReviewDb db,
       ChangeUpdate update, LabelTypes labelTypes, Change change, PatchSet ps,
       PatchSetInfo info, Iterable<Account.Id> wantReviewers,
@@ -185,7 +152,7 @@
       Iterable<Account.Id> wantReviewers) throws OrmException {
     PatchSet.Id psId = change.currentPatchSetId();
     return addReviewers(db, update, labelTypes, change, psId, false, null, null,
-        wantReviewers, getReviewers(db, notes).values());
+        wantReviewers, getReviewers(db, notes).all());
   }
 
   private List<PatchSetApproval> addReviewers(ReviewDb db, ChangeUpdate update,
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerSet.java b/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerSet.java
new file mode 100644
index 0000000..515cef7
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/ReviewerSet.java
@@ -0,0 +1,115 @@
+// 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;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
+import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
+
+import com.google.common.collect.HashBasedTable;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Table;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
+
+import java.sql.Timestamp;
+
+/**
+ * Set of reviewers on a change.
+ * <p>
+ * A given account may appear in multiple states and at different timestamps. No
+ * reviewers with state {@link ReviewerStateInternal#REMOVED} are ever exposed
+ * by this interface.
+ */
+public class ReviewerSet {
+  private static final ReviewerSet EMPTY = new ReviewerSet(
+      ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>of());
+
+  public static ReviewerSet fromApprovals(
+      Iterable<PatchSetApproval> approvals) {
+    PatchSetApproval first = null;
+    Table<ReviewerStateInternal, Account.Id, Timestamp> reviewers =
+        HashBasedTable.create();
+    for (PatchSetApproval psa : approvals) {
+      if (first == null) {
+        first = psa;
+      } else {
+        checkArgument(
+            first.getKey().getParentKey().getParentKey().equals(
+              psa.getKey().getParentKey().getParentKey()),
+            "multiple change IDs: %s, %s", first.getKey(), psa.getKey());
+      }
+      Account.Id id = psa.getAccountId();
+      if (psa.getValue() != 0) {
+        reviewers.put(REVIEWER, id, psa.getGranted());
+        reviewers.remove(CC, id);
+      } else if (!reviewers.contains(REVIEWER, id)) {
+        reviewers.put(CC, id, psa.getGranted());
+      }
+    }
+    return new ReviewerSet(reviewers);
+  }
+
+  public static ReviewerSet fromTable(
+      Table<ReviewerStateInternal, Account.Id, Timestamp> table) {
+    return new ReviewerSet(table);
+  }
+
+  public static ReviewerSet empty() {
+    return EMPTY;
+  }
+
+  private final ImmutableTable<ReviewerStateInternal, Account.Id, Timestamp>
+      table;
+  private ImmutableSet<Account.Id> accounts;
+
+  private ReviewerSet(Table<ReviewerStateInternal, Account.Id, Timestamp> table) {
+    this.table = ImmutableTable.copyOf(table);
+  }
+
+  public ImmutableSet<Account.Id> all() {
+    if (accounts == null) {
+      // Idempotent and immutable, don't bother locking.
+      accounts = ImmutableSet.copyOf(table.columnKeySet());
+    }
+    return accounts;
+  }
+
+  public ImmutableSet<Account.Id> byState(ReviewerStateInternal state) {
+    return table.row(state).keySet();
+  }
+
+  public ImmutableTable<ReviewerStateInternal, Account.Id, Timestamp>
+      asTable() {
+    return table;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return (o instanceof ReviewerSet) && table.equals(((ReviewerSet) o).table);
+  }
+
+  @Override
+  public int hashCode() {
+    return table.hashCode();
+  }
+
+  @Override
+  public String toString() {
+    return getClass().getSimpleName() + table;
+  }
+}
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java
index 568f816..f93bb72 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java
@@ -442,10 +442,10 @@
       out.removableReviewers = removableReviewers(ctl, out.labels.values());
 
       out.reviewers = new HashMap<>();
-      for (Map.Entry<ReviewerStateInternal, Collection<Account.Id>> e
-          : cd.reviewers().asMap().entrySet()) {
+      for (Map.Entry<ReviewerStateInternal, Map<Account.Id, Timestamp>> e
+          : cd.reviewers().asTable().rowMap().entrySet()) {
         out.reviewers.put(e.getKey().asReviewerState(),
-            toAccountInfo(e.getValue()));
+            toAccountInfo(e.getValue().keySet()));
       }
     }
 
@@ -617,7 +617,7 @@
     //  - They are an explicit reviewer.
     //  - They ever voted on this change.
     Set<Account.Id> allUsers = new HashSet<>();
-    allUsers.addAll(cd.reviewers().values());
+    allUsers.addAll(cd.reviewers().all());
     for (PatchSetApproval psa : cd.approvals().values()) {
       allUsers.add(psa.getAccountId());
     }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/ListReviewers.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/ListReviewers.java
index 1e3480f..9a0c691 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/ListReviewers.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/ListReviewers.java
@@ -51,7 +51,7 @@
     Map<Account.Id, ReviewerResource> reviewers = new LinkedHashMap<>();
     ReviewDb db = dbProvider.get();
     for (Account.Id accountId
-        : approvalsUtil.getReviewers(db, rsrc.getNotes()).values()) {
+        : approvalsUtil.getReviewers(db, rsrc.getNotes()).all()) {
       if (!reviewers.containsKey(accountId)) {
         reviewers.put(accountId, resourceFactory.create(rsrc, accountId));
       }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
index 3defdd7..ffbfc36 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/PatchSetInserter.java
@@ -19,10 +19,8 @@
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
 
-import com.google.common.collect.SetMultimap;
 import com.google.gerrit.common.ChangeHooks;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
-import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.ChangeMessage;
 import com.google.gerrit.reviewdb.client.PatchSet;
@@ -33,6 +31,7 @@
 import com.google.gerrit.server.ChangeMessagesUtil;
 import com.google.gerrit.server.ChangeUtil;
 import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.events.CommitReceivedEvent;
 import com.google.gerrit.server.git.BanCommit;
 import com.google.gerrit.server.git.BatchUpdate;
@@ -43,7 +42,6 @@
 import com.google.gerrit.server.git.validators.CommitValidators;
 import com.google.gerrit.server.mail.ReplacePatchSetSender;
 import com.google.gerrit.server.notedb.ChangeUpdate;
-import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.patch.PatchSetInfoFactory;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.RefControl;
@@ -106,7 +104,7 @@
   private PatchSet patchSet;
   private PatchSetInfo patchSetInfo;
   private ChangeMessage changeMessage;
-  private SetMultimap<ReviewerStateInternal, Account.Id> oldReviewers;
+  private ReviewerSet oldReviewers;
 
   @AssistedInject
   public PatchSetInserter(ChangeHooks hooks,
@@ -264,8 +262,8 @@
         cm.setFrom(ctx.getUser().getAccountId());
         cm.setPatchSet(patchSet, patchSetInfo);
         cm.setChangeMessage(changeMessage);
-        cm.addReviewers(oldReviewers.get(REVIEWER));
-        cm.addExtraCC(oldReviewers.get(CC));
+        cm.addReviewers(oldReviewers.byState(REVIEWER));
+        cm.addExtraCC(oldReviewers.byState(CC));
         cm.send();
       } catch (Exception err) {
         log.error("Cannot send email for new patch set on change "
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/PublishDraftPatchSet.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/PublishDraftPatchSet.java
index ff5185e..4304669 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/PublishDraftPatchSet.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/PublishDraftPatchSet.java
@@ -207,7 +207,7 @@
         throws OrmException, IOException {
       LabelTypes labelTypes = ctx.getControl().getLabelTypes();
       Collection<Account.Id> oldReviewers = approvalsUtil.getReviewers(
-          ctx.getDb(), ctx.getNotes()).values();
+          ctx.getDb(), ctx.getNotes()).all();
       RevCommit commit = ctx.getRevWalk().parseCommit(
           ObjectId.fromString(patchSet.getRevision().get()));
       patchSetInfo = patchSetInfoFactory.get(ctx.getRevWalk(), commit, psId);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java
index 74a8866..d45d260 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java
@@ -83,6 +83,6 @@
   private Collection<Account.Id> fetchAccountIds(ChangeResource rsrc)
       throws OrmException {
     return approvalsUtil.getReviewers(
-        dbProvider.get(), rsrc.getNotes()).values();
+        dbProvider.get(), rsrc.getNotes()).all();
   }
 }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/events/EventFactory.java b/gerrit-server/src/main/java/com/google/gerrit/server/events/EventFactory.java
index 5807c26..56daccc 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/events/EventFactory.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/events/EventFactory.java
@@ -203,7 +203,7 @@
   public void addAllReviewers(ReviewDb db, ChangeAttribute a, ChangeNotes notes)
       throws OrmException {
     Collection<Account.Id> reviewers =
-        approvalsUtil.getReviewers(db, notes).values();
+        approvalsUtil.getReviewers(db, notes).all();
     if (!reviewers.isEmpty()) {
       a.allReviewers = Lists.newArrayListWithCapacity(reviewers.size());
       for (Account.Id id : reviewers) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java b/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
index 367159d..ad543ea 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/mail/ChangeEmail.java
@@ -111,7 +111,7 @@
     appendText(velocifyFile("ChangeFooter.vm"));
     try {
       TreeSet<String> names = new TreeSet<>();
-      for (Account.Id who : changeData.reviewers().values()) {
+      for (Account.Id who : changeData.reviewers().all()) {
         names.add(getNameEmailFor(who));
       }
       for (String name : names) {
@@ -337,7 +337,7 @@
     }
 
     try {
-      for (Account.Id id : changeData.reviewers().values()) {
+      for (Account.Id id : changeData.reviewers().all()) {
         add(RecipientType.CC, id);
       }
     } catch (OrmException err) {
@@ -353,7 +353,7 @@
     }
 
     try {
-      for (Account.Id id : changeData.reviewers().get(REVIEWER)) {
+      for (Account.Id id : changeData.reviewers().byState(REVIEWER)) {
         add(RecipientType.CC, id);
       }
     } catch (OrmException err) {
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java b/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
index af8a3f69..a1274c3 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/mail/MailUtil.java
@@ -17,12 +17,11 @@
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
 import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
 
-import com.google.common.collect.Multimap;
 import com.google.gerrit.common.FooterConstants;
 import com.google.gerrit.common.errors.NoSuchAccountException;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.account.AccountResolver;
-import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gwtorm.server.OrmException;
 
 import org.eclipse.jgit.revwalk.FooterKey;
@@ -58,10 +57,10 @@
   }
 
   public static MailRecipients getRecipientsFromReviewers(
-      Multimap<ReviewerStateInternal, Account.Id> reviewers) {
+      ReviewerSet reviewers) {
     MailRecipients recipients = new MailRecipients();
-    recipients.reviewers.addAll(reviewers.get(REVIEWER));
-    recipients.cc.addAll(reviewers.get(CC));
+    recipients.reviewers.addAll(reviewers.byState(REVIEWER));
+    recipients.cc.addAll(reviewers.byState(CC));
     return recipients;
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
index 0dfd8c9..1f40498 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeBundle.java
@@ -40,6 +40,7 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Ordering;
 import com.google.common.collect.Sets;
+import com.google.common.collect.Table;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
@@ -50,6 +51,7 @@
 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.gwtorm.client.Column;
 import com.google.gwtorm.server.OrmException;
 
@@ -59,6 +61,7 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
@@ -84,12 +87,15 @@
       throws OrmException {
     db.changes().beginTransaction(id);
     try {
+      List<PatchSetApproval> approvals =
+          db.patchSetApprovals().byChange(id).toList();
       return new ChangeBundle(
           db.changes().get(id),
           db.changeMessages().byChange(id),
           db.patchSets().byChange(id),
-          db.patchSetApprovals().byChange(id),
+          approvals,
           db.patchComments().byChange(id),
+          ReviewerSet.fromApprovals(approvals),
           Source.REVIEW_DB);
     } finally {
       db.rollback();
@@ -106,6 +112,7 @@
         Iterables.concat(
             plcUtil.draftByChange(null, notes),
             plcUtil.publishedByChange(null, notes)),
+        notes.getReviewers(),
         Source.NOTE_DB);
   }
 
@@ -156,7 +163,6 @@
     return CHANGE_MESSAGE_ORDER.immutableSortedCopy(in);
   }
 
-
   private static TreeMap<PatchSet.Id, PatchSet> patchSetMap(Iterable<PatchSet> in) {
     TreeMap<PatchSet.Id, PatchSet> out = new TreeMap<>(
         new Comparator<PatchSet.Id>() {
@@ -256,6 +262,7 @@
       patchSetApprovals;
   private final ImmutableMap<PatchLineComment.Key, PatchLineComment>
       patchLineComments;
+  private final ReviewerSet reviewers;
   private final Source source;
 
   public ChangeBundle(
@@ -264,6 +271,7 @@
       Iterable<PatchSet> patchSets,
       Iterable<PatchSetApproval> patchSetApprovals,
       Iterable<PatchLineComment> patchLineComments,
+      ReviewerSet reviewers,
       Source source) {
     this.change = checkNotNull(change);
     this.changeMessages = changeMessageList(changeMessages);
@@ -272,6 +280,7 @@
         ImmutableMap.copyOf(patchSetApprovalMap(patchSetApprovals));
     this.patchLineComments =
         ImmutableMap.copyOf(patchLineCommentMap(patchLineComments));
+    this.reviewers = checkNotNull(reviewers);
     this.source = checkNotNull(source);
 
     for (ChangeMessage m : this.changeMessages) {
@@ -309,6 +318,10 @@
     return patchLineComments.values();
   }
 
+  public ReviewerSet getReviewers() {
+    return reviewers;
+  }
+
   public Source getSource() {
     return source;
   }
@@ -319,6 +332,7 @@
     diffChangeMessages(diffs, this, o);
     diffPatchSets(diffs, this, o);
     diffPatchSetApprovals(diffs, this, o);
+    diffReviewers(diffs, this, o);
     diffPatchLineComments(diffs, this, o);
     return ImmutableList.copyOf(diffs);
   }
@@ -661,6 +675,39 @@
     }
   }
 
+  @AutoValue
+  static abstract class ReviewerKey {
+    private static Map<ReviewerKey, Timestamp> toMap(ReviewerSet reviewers) {
+      Map<ReviewerKey, Timestamp> result = new HashMap<>();
+      for (Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> c :
+          reviewers.asTable().cellSet()) {
+        result.put(new AutoValue_ChangeBundle_ReviewerKey(
+            c.getRowKey(), c.getColumnKey()), c.getValue());
+      }
+      return result;
+    }
+
+    abstract ReviewerStateInternal state();
+    abstract Account.Id account();
+
+    @Override
+    public String toString() {
+      return state() + "," + account();
+    }
+  }
+
+  private static void diffReviewers(List<String> diffs,
+      ChangeBundle bundleA, ChangeBundle bundleB) {
+    Map<ReviewerKey, Timestamp> as = ReviewerKey.toMap(bundleA.reviewers);
+    Map<ReviewerKey, Timestamp> bs = ReviewerKey.toMap(bundleB.reviewers);
+    for (ReviewerKey k : diffKeySets(diffs, as, bs)) {
+      Timestamp a = as.get(k);
+      Timestamp b = bs.get(k);
+      String desc = describe(k);
+      diffTimestamps(diffs, desc, bundleA, a, bundleB, b, "timestamp");
+    }
+  }
+
   private static void diffPatchLineComments(List<String> diffs,
       ChangeBundle bundleA, ChangeBundle bundleB) {
     Map<PatchLineComment.Key, PatchLineComment> as =
@@ -825,9 +872,14 @@
   private static String keyClass(Object obj) {
     Class<?> clazz = obj.getClass();
     String name = clazz.getSimpleName();
-    checkArgument(name.equals("Key") || name.equals("Id"),
+    checkArgument(name.endsWith("Key") || name.endsWith("Id"),
         "not an Id/Key class: %s", name);
-    return clazz.getEnclosingClass().getSimpleName() + "." + name;
+    if (name.equals("Key") || name.equals("Id")) {
+      return clazz.getEnclosingClass().getSimpleName() + "." + name;
+    } else if (name.startsWith("AutoValue_")) {
+      return name.substring(name.lastIndexOf('_') + 1);
+    }
+    return name;
   }
 
   @Override
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
index a6cd8fa..926194b 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -28,7 +28,6 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
@@ -36,6 +35,7 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Multimaps;
 import com.google.common.collect.Ordering;
+import com.google.common.collect.Tables;
 import com.google.common.util.concurrent.AsyncFunction;
 import com.google.common.util.concurrent.CheckedFuture;
 import com.google.common.util.concurrent.Futures;
@@ -55,6 +55,7 @@
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.reviewdb.server.ReviewDbUtil;
+import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.git.RefCache;
 import com.google.gerrit.server.git.RepoRefCache;
 import com.google.gerrit.server.project.NoSuchChangeException;
@@ -381,7 +382,7 @@
 
   private ImmutableSortedMap<PatchSet.Id, PatchSet> patchSets;
   private ImmutableListMultimap<PatchSet.Id, PatchSetApproval> approvals;
-  private ImmutableSetMultimap<ReviewerStateInternal, Account.Id> reviewers;
+  private ReviewerSet reviewers;
   private ImmutableList<Account.Id> allPastReviewers;
   private ImmutableList<SubmitRecord> submitRecords;
   private ImmutableList<ChangeMessage> allChangeMessages;
@@ -420,7 +421,7 @@
     return approvals;
   }
 
-  public ImmutableSetMultimap<ReviewerStateInternal, Account.Id> getReviewers() {
+  public ReviewerSet getReviewers() {
     return reviewers;
   }
 
@@ -583,13 +584,7 @@
     } else {
       hashtags = ImmutableSet.of();
     }
-    ImmutableSetMultimap.Builder<ReviewerStateInternal, Account.Id> reviewers =
-        ImmutableSetMultimap.builder();
-    for (Map.Entry<Account.Id, ReviewerStateInternal> e
-        : parser.reviewers.entrySet()) {
-      reviewers.put(e.getValue(), e.getKey());
-    }
-    this.reviewers = reviewers.build();
+    this.reviewers = ReviewerSet.fromTable(Tables.transpose(parser.reviewers));
     this.allPastReviewers = ImmutableList.copyOf(parser.allPastReviewers);
 
     submitRecords = ImmutableList.copyOf(parser.submitRecords);
@@ -598,7 +593,7 @@
   @Override
   protected void loadDefaults() {
     approvals = ImmutableListMultimap.of();
-    reviewers = ImmutableSetMultimap.of();
+    reviewers = ReviewerSet.empty();
     submitRecords = ImmutableList.of();
     allChangeMessages = ImmutableList.of();
     changeMessagesByPatchSet = ImmutableListMultimap.of();
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
index 9d9e180..02dd441 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
@@ -36,6 +36,7 @@
 import com.google.common.base.Splitter;
 import com.google.common.base.Supplier;
 import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.HashBasedTable;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableSet;
@@ -94,7 +95,7 @@
   private static final RevId PARTIAL_PATCH_SET =
       new RevId("INVALID PARTIAL PATCH SET");
 
-  final Map<Account.Id, ReviewerStateInternal> reviewers;
+  final Table<Account.Id, ReviewerStateInternal, Timestamp> reviewers;
   final List<Account.Id> allPastReviewers;
   final List<SubmitRecord> submitRecords;
   final Multimap<RevId, PatchLineComment> comments;
@@ -134,7 +135,7 @@
     this.noteUtil = noteUtil;
     this.metrics = metrics;
     approvals = new HashMap<>();
-    reviewers = new LinkedHashMap<>();
+    reviewers = HashBasedTable.create();
     allPastReviewers = new ArrayList<>();
     submitRecords = Lists.newArrayListWithExpectedSize(1);
     allChangeMessages = new ArrayList<>();
@@ -156,7 +157,7 @@
         parse(commit);
       }
       parseNotes();
-      allPastReviewers.addAll(reviewers.keySet());
+      allPastReviewers.addAll(reviewers.rowKeySet());
       pruneReviewers();
       updatePatchSetStates();
       checkMandatoryFooters();
@@ -262,7 +263,7 @@
 
     for (ReviewerStateInternal state : ReviewerStateInternal.values()) {
       for (String line : commit.getFooterLineValues(state.getFooterKey())) {
-        parseReviewer(state, line);
+        parseReviewer(ts, state, line);
       }
       // Don't update timestamp when a reviewer was added, matching RevewDb
       // behavior.
@@ -698,27 +699,27 @@
     return noteUtil.parseIdent(commit.getAuthorIdent(), id);
   }
 
-  private void parseReviewer(ReviewerStateInternal state, String line)
-      throws ConfigInvalidException {
+  private void parseReviewer(Timestamp ts, ReviewerStateInternal state,
+      String line) throws ConfigInvalidException {
     PersonIdent ident = RawParseUtils.parsePersonIdent(line);
     if (ident == null) {
       throw invalidFooter(state.getFooterKey(), line);
     }
     Account.Id accountId = noteUtil.parseIdent(ident, id);
-    if (!reviewers.containsKey(accountId)) {
-      reviewers.put(accountId, state);
+    if (!reviewers.containsRow(accountId)) {
+      reviewers.put(accountId, state, ts);
     }
   }
 
   private void pruneReviewers() {
-    Iterator<Map.Entry<Account.Id, ReviewerStateInternal>> rit =
-        reviewers.entrySet().iterator();
+    Iterator<Table.Cell<Account.Id, ReviewerStateInternal, Timestamp>> rit =
+        reviewers.cellSet().iterator();
     while (rit.hasNext()) {
-      Map.Entry<Account.Id, ReviewerStateInternal> e = rit.next();
-      if (e.getValue() == ReviewerStateInternal.REMOVED) {
+      Table.Cell<Account.Id, ReviewerStateInternal, Timestamp> e = rit.next();
+      if (e.getColumnKey() == ReviewerStateInternal.REMOVED) {
         rit.remove();
         for (Table<Account.Id, ?, ?> curr : approvals.values()) {
-          curr.rowKeySet().remove(e.getKey());
+          curr.rowKeySet().remove(e.getRowKey());
         }
       }
     }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeRebuilderImpl.java b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeRebuilderImpl.java
index 9aa69bf..5f16eb4 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeRebuilderImpl.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeRebuilderImpl.java
@@ -36,6 +36,7 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Ordering;
 import com.google.common.collect.Sets;
+import com.google.common.collect.Table;
 import com.google.common.primitives.Ints;
 import com.google.gerrit.common.FormatUtil;
 import com.google.gerrit.common.Nullable;
@@ -277,6 +278,11 @@
       }
     }
 
+    for (Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> r :
+        bundle.getReviewers().asTable().cellSet()) {
+      events.add(new ReviewerEvent(r, change.getCreatedOn()));
+    }
+
     Change noteDbChange = new Change(null, null, null, null, null);
     for (ChangeMessage msg : bundle.getChangeMessages()) {
       if (msg.getPatchSetId() == null || psIds.contains(msg.getPatchSetId())) {
@@ -714,6 +720,33 @@
     }
   }
 
+  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;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/project/ChangeControl.java b/gerrit-server/src/main/java/com/google/gerrit/server/project/ChangeControl.java
index 4bda245..62c6d5e 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/project/ChangeControl.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/project/ChangeControl.java
@@ -340,7 +340,7 @@
   public boolean isReviewer(ReviewDb db, @Nullable ChangeData cd)
       throws OrmException {
     if (getUser().isIdentifiedUser()) {
-      Collection<Account.Id> results = changeData(db, cd).reviewers().values();
+      Collection<Account.Id> results = changeData(db, cd).reviewers().all();
       return results.contains(getUser().getAccountId());
     }
     return false;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
index ed7b134..93a16ad 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -30,7 +30,6 @@
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Multimap;
-import com.google.common.collect.SetMultimap;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.data.SubmitRecord;
 import com.google.gerrit.common.data.SubmitTypeRecord;
@@ -50,13 +49,13 @@
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.PatchLineCommentsUtil;
 import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.StarredChangesUtil;
 import com.google.gerrit.server.change.MergeabilityCache;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.NotesMigration;
-import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.patch.PatchList;
 import com.google.gerrit.server.patch.PatchListCache;
 import com.google.gerrit.server.patch.PatchListEntry;
@@ -905,8 +904,7 @@
     return Optional.absent();
   }
 
-  public SetMultimap<ReviewerStateInternal, Account.Id> reviewers()
-      throws OrmException {
+  public ReviewerSet reviewers() throws OrmException {
     return approvalsUtil.getReviewers(notes(), approvals().values());
   }
 
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerPredicate.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerPredicate.java
index eb07250..2da8c54 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerPredicate.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerPredicate.java
@@ -40,7 +40,7 @@
         object.change().getStatus() == Change.Status.DRAFT) {
       return false;
     }
-    for (Account.Id accountId : object.reviewers().values()) {
+    for (Account.Id accountId : object.reviewers().all()) {
       if (id.equals(accountId)) {
         return true;
       }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerinPredicate.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerinPredicate.java
index eb93451..76a02432 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerinPredicate.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ReviewerinPredicate.java
@@ -37,7 +37,7 @@
 
   @Override
   public boolean match(final ChangeData object) throws OrmException {
-    for (Account.Id accountId : object.reviewers().values()) {
+    for (Account.Id accountId : object.reviewers().all()) {
       IdentifiedUser reviewer = userFactory.create(accountId);
       if (reviewer.getEffectiveGroups().contains(uuid)) {
         return true;
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeBundleTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeBundleTest.java
index ea1120f..4306d74 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeBundleTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeBundleTest.java
@@ -14,14 +14,18 @@
 
 package com.google.gerrit.server.notedb;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.common.TimeUtil.roundToSecond;
 import static com.google.gerrit.server.notedb.ChangeBundle.Source.NOTE_DB;
 import static com.google.gerrit.server.notedb.ChangeBundle.Source.REVIEW_DB;
+import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
+import com.google.common.collect.HashBasedTable;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Table;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
@@ -33,6 +37,7 @@
 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.testutil.TestChanges;
 import com.google.gerrit.testutil.TestTimeUtil;
 import com.google.gwtorm.client.KeyUtil;
@@ -113,9 +118,9 @@
     Change c2 = TestChanges.newChange(project, accountId);
     int id2 = c2.getId().get();
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertDiffs(b1, b2,
         "changeId differs for Changes: {" + id1 + "} != {" + id2 + "}",
@@ -131,9 +136,9 @@
         new Project.NameKey("project"), new Account.Id(100));
     Change c2 = clone(c1);
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertNoDiffs(b1, b2);
 
@@ -153,9 +158,9 @@
 
     // Both are ReviewDb, exact timestamp match is required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "createdOn differs for Change.Id " + c1.getId() + ":"
             + " {2009-09-30 17:00:01.0} != {2009-09-30 17:00:02.0}",
@@ -164,9 +169,9 @@
 
     // One NoteDb, slop is allowed.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
 
@@ -175,9 +180,9 @@
     Change c3 = clone(c1);
     c3.setLastUpdatedOn(TimeUtil.nowTs());
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     ChangeBundle b3 = new ChangeBundle(c3, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     String msg = "effective last updated time differs for Change.Id "
         + c1.getId() + " in NoteDb vs. ReviewDb:"
         + " {2009-09-30 17:00:01.0} != {2009-09-30 17:00:10.0}";
@@ -197,27 +202,27 @@
 
     // Both ReviewDb, exact match required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "originalSubject differs for Change.Id " + c1.getId() + ":"
             + " {Original A} != {Original B}");
 
     // Both NoteDb, exact match required.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "originalSubject differs for Change.Id " + c1.getId() + ":"
             + " {Original A} != {Original B}");
 
     // One ReviewDb, one NoteDb, original subject is ignored.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
   }
@@ -233,25 +238,25 @@
 
     // Both ReviewDb, exact match required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "topic differs for Change.Id " + c1.getId() + ":"
             + " {} != {null}");
 
     // Topic ignored if ReviewDb is empty and NoteDb is null.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
 
     // Exact match still required if NoteDb has empty value (not realistic).
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "topic differs for Change.Id " + c1.getId() + ":"
             + " {} != {null}");
@@ -260,9 +265,9 @@
     Change c3 = clone(c1);
     c3.setTopic("topic");
     b1 = new ChangeBundle(c3, messages(), patchSets(), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "topic differs for Change.Id " + c1.getId() + ":"
             + " {topic} != {null}");
@@ -284,16 +289,16 @@
 
     // Both ReviewDb, exact match required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(),
-        approvals(a), comments(), REVIEW_DB);
+        approvals(a), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(),
-        approvals(a), comments(), REVIEW_DB);
+        approvals(a), comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "effective last updated time differs for Change.Id " + c1.getId() + ":"
             + " {2009-09-30 17:00:00.0} != {2009-09-30 17:00:06.0}");
 
     // NoteDb allows latest timestamp from all entities in bundle.
     b2 = new ChangeBundle(c2, messages(), patchSets(),
-        approvals(a), comments(), NOTE_DB);
+        approvals(a), comments(), reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
   }
 
@@ -314,18 +319,18 @@
     // ReviewDb has later lastUpdatedOn timestamp than NoteDb, allowed since
     // NoteDb matches the latest timestamp of a non-Change entity.
     ChangeBundle b1 = new ChangeBundle(c2, messages(), patchSets(),
-        approvals(a), comments(), REVIEW_DB);
+        approvals(a), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c1, messages(), patchSets(),
-        approvals(a), comments(), NOTE_DB);
+        approvals(a), comments(), reviewers(), NOTE_DB);
     assertThat(b1.getChange().getLastUpdatedOn())
         .isGreaterThan(b2.getChange().getLastUpdatedOn());
     assertNoDiffs(b1, b2);
 
     // Timestamps must actually match if Change is the only entity.
     b1 = new ChangeBundle(c2, messages(), patchSets(), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c1, messages(), patchSets(), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "effective last updated time differs for Change.Id " + c1.getId()
             + " in NoteDb vs. ReviewDb:"
@@ -344,25 +349,25 @@
 
     // Both ReviewDb, exact match required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "subject differs for Change.Id " + c1.getId() + ":"
             + " {Change subject} != {Change sub}");
 
     // ReviewDb has shorter subject, allowed.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // NoteDb has shorter subject, not allowed.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "subject differs for Change.Id " + c1.getId() + ":"
             + " {Change subject} != {Change sub}");
@@ -379,18 +384,18 @@
 
     // Both ReviewDb, exact match required.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "subject differs for Change.Id " + c1.getId() + ":"
             + " {Change subject} != {   Change subject}");
 
     // ReviewDb is missing leading spaces, allowed.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
   }
@@ -406,18 +411,18 @@
 
     // Both ReviewDb.
     ChangeBundle b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "subject differs for Change.Id " + c1.getId() + ":"
             + " {Change subject} != {\tChange subject}");
 
     // One NoteDb.
     b1 = new ChangeBundle(c1, messages(), patchSets(), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c2, messages(), patchSets(), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "subject differs for Change.Id " + c1.getId() + ":"
             + " {Change subject} != {\tChange subject}");
@@ -437,9 +442,9 @@
         new ChangeMessage.Key(c.getId(), "uuid2"),
         accountId, TimeUtil.nowTs(), c.currentPatchSetId());
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertDiffs(b1, b2,
         "ChangeMessage.Key sets differ:"
@@ -455,9 +460,9 @@
     cm1.setMessage("message 1");
     ChangeMessage cm2 = clone(cm1);
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertNoDiffs(b1, b2);
 
@@ -479,9 +484,9 @@
     cm2.getKey().set("uuid2");
 
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     // Both are ReviewDb, exact UUID match is required.
     assertDiffs(b1, b2,
         "ChangeMessage.Key sets differ:"
@@ -489,9 +494,9 @@
 
     // One NoteDb, UUIDs are ignored.
     b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
   }
 
@@ -510,18 +515,18 @@
 
     // Both ReviewDb: Uses same keySet diff as other types.
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1, cm2), latest(c),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "ChangeMessage.Key sets differ: [" + id
         + ",uuid2] only in A; [] only in B");
 
     // One NoteDb: UUIDs in keys can't be used for comparison, just diff counts.
     b1 = new ChangeBundle(c, messages(cm1, cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "ChangeMessages differ for Change.Id " + id + "\n"
             + "Only in A:\n  " + cm2);
@@ -544,9 +549,9 @@
     cm3.getKey().set("uuid2"); // Differs only in UUID.
 
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1, cm3), latest(c),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2, cm3), latest(c),
-        approvals(), comments(), NOTE_DB);
+        approvals(), comments(), reviewers(), NOTE_DB);
     // Implementation happens to pair up cm1 in b1 with cm3 in b2 because it
     // depends on iteration order and doesn't care about UUIDs. The important
     // thing is that there's some diff.
@@ -572,18 +577,18 @@
 
     // Both are ReviewDb, exact timestamp match is required.
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "writtenOn differs for ChangeMessage.Key " + c.getId() + ",uuid1:"
             + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:03.0}");
 
     // One NoteDb, slop is allowed.
     b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
 
@@ -592,9 +597,9 @@
     ChangeMessage cm3 = clone(cm1);
     cm3.setWrittenOn(TimeUtil.nowTs());
     b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     ChangeBundle b3 = new ChangeBundle(c, messages(cm3), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     int id = c.getId().get();
     assertDiffs(b1, b3,
         "ChangeMessages differ for Change.Id " + id + "\n"
@@ -619,9 +624,9 @@
     cm2.setPatchSetId(null);
 
     ChangeBundle b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     // Both are ReviewDb, exact patch set ID match is required.
     assertDiffs(b1, b2,
@@ -630,16 +635,16 @@
 
     // Null patch set ID on ReviewDb is ignored.
     b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // Null patch set ID on NoteDb is not ignored (but is not realistic).
     b1 = new ChangeBundle(c, messages(cm1), latest(c), approvals(), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c, messages(cm2), latest(c), approvals(), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     assertDiffs(b1, b2,
         "ChangeMessages differ for Change.Id " + id + "\n"
             + "Only in A:\n  " + cm1 + "\n"
@@ -665,9 +670,9 @@
     ps2.setCreatedOn(TimeUtil.nowTs());
 
     ChangeBundle b1 = new ChangeBundle(c, messages(), patchSets(ps2),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), patchSets(ps1, ps2),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
 
     assertDiffs(b1, b2,
         "PatchSet.Id sets differ:"
@@ -683,9 +688,9 @@
     ps1.setCreatedOn(TimeUtil.nowTs());
     PatchSet ps2 = clone(ps1);
     ChangeBundle b1 = new ChangeBundle(c, messages(), patchSets(ps1),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), patchSets(ps2),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
 
     assertNoDiffs(b1, b2);
 
@@ -709,18 +714,18 @@
 
     // Both are ReviewDb, exact timestamp match is required.
     ChangeBundle b1 = new ChangeBundle(c, messages(), patchSets(ps1),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), patchSets(ps2),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "createdOn differs for PatchSet.Id " + c.getId() + ",1:"
             + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:03.0}");
 
     // One NoteDb, slop is allowed.
     b1 = new ChangeBundle(c, messages(), patchSets(ps1), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), patchSets(ps2), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // But not too much slop.
@@ -728,9 +733,9 @@
     PatchSet ps3 = clone(ps1);
     ps3.setCreatedOn(TimeUtil.nowTs());
     b1 = new ChangeBundle(c, messages(), patchSets(ps1), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     ChangeBundle b3 = new ChangeBundle(c, messages(), patchSets(ps3),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     String msg = "createdOn differs for PatchSet.Id " + c.getId()
         + ",1 in NoteDb vs. ReviewDb:"
         + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:10.0}";
@@ -752,16 +757,16 @@
     ps2.setPushCertificate(ps2.getPushCertificate() + "\n\n");
 
     ChangeBundle b1 = new ChangeBundle(c, messages(), patchSets(ps1),
-        approvals(), comments(), NOTE_DB);
+        approvals(), comments(), reviewers(), NOTE_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), patchSets(ps2),
-        approvals(), comments(), REVIEW_DB);
+        approvals(), comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
 
     b1 = new ChangeBundle(c, messages(), patchSets(ps1), approvals(),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     b2 = new ChangeBundle(c, messages(), patchSets(ps2), approvals(),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
   }
@@ -793,24 +798,24 @@
 
     // Both ReviewDb.
     ChangeBundle b1 = new ChangeBundle(c, messages(), patchSets(ps1),
-        approvals(a1), comments(), REVIEW_DB);
+        approvals(a1), comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), patchSets(ps1, ps2),
-        approvals(a1, a2), comments(), REVIEW_DB);
+        approvals(a1, a2), comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // One NoteDb.
     b1 = new ChangeBundle(c, messages(), patchSets(ps1), approvals(a1),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), patchSets(ps1, ps2), approvals(a1, a2),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
 
     // Both NoteDb.
     b1 = new ChangeBundle(c, messages(), patchSets(ps1), approvals(a1),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), patchSets(ps1, ps2), approvals(a1, a2),
-        comments(), NOTE_DB);
+        comments(), reviewers(), NOTE_DB);
     assertNoDiffs(b1, b2);
   }
 
@@ -830,9 +835,9 @@
         TimeUtil.nowTs());
 
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertDiffs(b1, b2,
         "PatchSetApproval.Key sets differ:"
@@ -850,9 +855,9 @@
         TimeUtil.nowTs());
     PatchSetApproval a2 = clone(a1);
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
 
     assertNoDiffs(b1, b2);
 
@@ -877,9 +882,9 @@
 
     // Both are ReviewDb, exact timestamp match is required.
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "granted differs for PatchSetApproval.Key "
             + c.getId() + "%2C1,100,Code-Review:"
@@ -887,9 +892,9 @@
 
     // One NoteDb, slop is allowed.
     b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // But not too much slop.
@@ -897,9 +902,9 @@
     PatchSetApproval a3 = clone(a1);
     a3.setGranted(TimeUtil.nowTs());
     b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     ChangeBundle b3 = new ChangeBundle(c, messages(), latest(c), approvals(a3),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     String msg = "granted differs for PatchSetApproval.Key "
         + c.getId() + "%2C1,100,Code-Review in NoteDb vs. ReviewDb:"
         + " {2009-09-30 17:00:07.0} != {2009-09-30 17:00:15.0}";
@@ -923,9 +928,9 @@
 
     // Both are ReviewDb, exact match is required.
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2),
-        comments(), REVIEW_DB);
+        comments(), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "granted differs for PatchSetApproval.Key "
             + c.getId() + "%2C1,100,Code-Review:"
@@ -933,14 +938,91 @@
 
     // Truncating NoteDb timestamp is allowed.
     b1 = new ChangeBundle(c, messages(), latest(c), approvals(a1), comments(),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), latest(c), approvals(a2), comments(),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
     assertNoDiffs(b2, b1);
   }
 
   @Test
+  public void diffReviewerKeySets() throws Exception {
+    Change c = TestChanges.newChange(project, accountId);
+    Timestamp now = TimeUtil.nowTs();
+    ReviewerSet r1 = reviewers(REVIEWER, new Account.Id(1), now);
+    ReviewerSet r2 = reviewers(REVIEWER, new Account.Id(2), now);
+
+    ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r1, REVIEW_DB);
+    ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r2, REVIEW_DB);
+    assertNoDiffs(b1, b1);
+    assertNoDiffs(b2, b2);
+    assertDiffs(b1, b2,
+        "ReviewerKey sets differ:"
+            + " [REVIEWER,1] only in A;"
+            + " [REVIEWER,2] only in B");
+  }
+
+  @Test
+  public void diffReviewerTimestamps() throws Exception {
+    Change c = TestChanges.newChange(project, accountId);
+    ReviewerSet r1 = reviewers(REVIEWER, new Account.Id(1), TimeUtil.nowTs());
+    ReviewerSet r2 = reviewers(REVIEWER, new Account.Id(1), TimeUtil.nowTs());
+
+    ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r1, REVIEW_DB);
+    ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r2, REVIEW_DB);
+    assertDiffs(b1, b2,
+        "timestamp differs for ReviewerKey REVIEWER,1:"
+            + " {2009-09-30 17:00:06.0} != {2009-09-30 17:00:12.0}");
+
+    b1 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(), r1,
+        REVIEW_DB);
+    b2 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(), r2,
+        NOTE_DB);
+    assertDiffs(b1, b2,
+        "timestamp differs for ReviewerKey REVIEWER,1 in NoteDb vs. ReviewDb:"
+            + " {2009-09-30 17:00:12.0} != {2009-09-30 17:00:06.0}");
+  }
+
+  @Test
+  public void diffReviewerTimestampsAllowsSlop() throws Exception {
+    subWindowResolution();
+    Change c = TestChanges.newChange(project, accountId);
+    ReviewerSet r1 = reviewers(REVIEWER, new Account.Id(1), TimeUtil.nowTs());
+    ReviewerSet r2 = reviewers(REVIEWER, new Account.Id(1), TimeUtil.nowTs());
+
+    // Both are ReviewDb, exact timestamp match is required.
+    ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r1, REVIEW_DB);
+    ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r2, REVIEW_DB);
+    assertDiffs(b1, b2,
+        "timestamp differs for ReviewerKey REVIEWER,1:"
+            + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:03.0}");
+
+    // One NoteDb, slop is allowed
+    b1 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(), r1,
+        NOTE_DB);
+    b2 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(), r2,
+        REVIEW_DB);
+    assertNoDiffs(b1, b2);
+
+    // But not too much slop.
+    superWindowResolution();
+    ReviewerSet r3 = reviewers(REVIEWER, new Account.Id(1), TimeUtil.nowTs());
+    b1 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(), r1,
+        NOTE_DB);
+    ChangeBundle b3 = new ChangeBundle(c, messages(), latest(c), approvals(),
+        comments(), r3, REVIEW_DB);
+    assertDiffs(b1, b3,
+        "timestamp differs for ReviewerKey REVIEWER,1 in NoteDb vs. ReviewDb:"
+            + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:10.0}");
+  }
+
+  @Test
   public void diffPatchLineCommentKeySets() throws Exception {
     Change c = TestChanges.newChange(project, accountId);
     int id = c.getId().get();
@@ -954,9 +1036,9 @@
         5, accountId, null, TimeUtil.nowTs());
 
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c1), REVIEW_DB);
+        comments(c1), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c2), REVIEW_DB);
+        comments(c2), reviewers(), REVIEW_DB);
 
     assertDiffs(b1, b2,
         "PatchLineComment.Key sets differ:"
@@ -973,9 +1055,9 @@
         5, accountId, null, TimeUtil.nowTs());
     PatchLineComment c2 = clone(c1);
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c1), REVIEW_DB);
+        comments(c1), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c2), REVIEW_DB);
+        comments(c2), reviewers(), REVIEW_DB);
 
     assertNoDiffs(b1, b2);
 
@@ -999,9 +1081,9 @@
 
     // Both are ReviewDb, exact timestamp match is required.
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c1), REVIEW_DB);
+        comments(c1), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c2), REVIEW_DB);
+        comments(c2), reviewers(), REVIEW_DB);
     assertDiffs(b1, b2,
         "writtenOn differs for PatchLineComment.Key "
             + c.getId() + ",1,filename,uuid:"
@@ -1009,9 +1091,9 @@
 
     // One NoteDb, slop is allowed.
     b1 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(c1),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     b2 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(c2),
-        REVIEW_DB);
+        reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
 
     // But not too much slop.
@@ -1019,9 +1101,9 @@
     PatchLineComment c3 = clone(c1);
     c3.setWrittenOn(TimeUtil.nowTs());
     b1 = new ChangeBundle(c, messages(), latest(c), approvals(), comments(c1),
-        NOTE_DB);
+        reviewers(), NOTE_DB);
     ChangeBundle b3 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c3), REVIEW_DB);
+        comments(c3), reviewers(), REVIEW_DB);
     String msg = "writtenOn differs for PatchLineComment.Key " + c.getId()
         + ",1,filename,uuid in NoteDb vs. ReviewDb:"
         + " {2009-09-30 17:00:02.0} != {2009-09-30 17:00:10.0}";
@@ -1043,9 +1125,9 @@
         5, accountId, null, TimeUtil.nowTs());
 
     ChangeBundle b1 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c1, c2), REVIEW_DB);
+        comments(c1, c2), reviewers(), REVIEW_DB);
     ChangeBundle b2 = new ChangeBundle(c, messages(), latest(c), approvals(),
-        comments(c1), REVIEW_DB);
+        comments(c1), reviewers(), REVIEW_DB);
     assertNoDiffs(b1, b2);
   }
 
@@ -1085,6 +1167,17 @@
     return Arrays.asList(ents);
   }
 
+  private static ReviewerSet reviewers(Object... ents) {
+    checkArgument(ents.length % 3 == 0);
+    Table<ReviewerStateInternal, Account.Id, Timestamp> t =
+        HashBasedTable.create();
+    for (int i = 0; i < ents.length; i += 3) {
+      t.put((ReviewerStateInternal) ents[i], (Account.Id) ents[i + 1],
+          (Timestamp) ents[i + 2]);
+    }
+    return ReviewerSet.fromTable(t);
+  }
+
   private static List<PatchLineComment> comments(PatchLineComment... ents) {
     return Arrays.asList(ents);
   }
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
index 3f77498..1f54f55 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java
@@ -28,7 +28,7 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.ImmutableSetMultimap;
+import com.google.common.collect.ImmutableTable;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Lists;
@@ -46,6 +46,7 @@
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
 import com.google.gerrit.testutil.TestChanges;
 import com.google.gwtorm.server.OrmException;
@@ -392,10 +393,12 @@
     update.commit();
 
     ChangeNotes notes = newNotes(c);
-    assertThat(notes.getReviewers()).isEqualTo(
-        ImmutableSetMultimap.of(
-          REVIEWER, new Account.Id(1),
-          REVIEWER, new Account.Id(2)));
+    Timestamp ts = new Timestamp(update.getWhen().getTime());
+    assertThat(notes.getReviewers()).isEqualTo(ReviewerSet.fromTable(
+        ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>builder()
+            .put(REVIEWER, new Account.Id(1), ts)
+            .put(REVIEWER, new Account.Id(2), ts)
+            .build()));
   }
 
   @Test
@@ -407,10 +410,12 @@
     update.commit();
 
     ChangeNotes notes = newNotes(c);
-    assertThat(notes.getReviewers()).isEqualTo(
-        ImmutableSetMultimap.of(
-            REVIEWER, new Account.Id(1),
-            CC, new Account.Id(2)));
+    Timestamp ts = new Timestamp(update.getWhen().getTime());
+    assertThat(notes.getReviewers()).isEqualTo(ReviewerSet.fromTable(
+        ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>builder()
+            .put(REVIEWER, new Account.Id(1), ts)
+            .put(CC, new Account.Id(2), ts)
+            .build()));
   }
 
   @Test
@@ -421,16 +426,18 @@
     update.commit();
 
     ChangeNotes notes = newNotes(c);
-    assertThat(notes.getReviewers()).isEqualTo(
-        ImmutableSetMultimap.of(REVIEWER, new Account.Id(2)));
+    Timestamp ts = new Timestamp(update.getWhen().getTime());
+    assertThat(notes.getReviewers()).isEqualTo(ReviewerSet.fromTable(
+        ImmutableTable.of(REVIEWER, new Account.Id(2), ts)));
 
     update = newUpdate(c, otherUser);
     update.putReviewer(otherUser.getAccount().getId(), CC);
     update.commit();
 
     notes = newNotes(c);
-    assertThat(notes.getReviewers()).isEqualTo(
-        ImmutableSetMultimap.of(CC, new Account.Id(2)));
+    ts = new Timestamp(update.getWhen().getTime());
+    assertThat(notes.getReviewers()).isEqualTo(ReviewerSet.fromTable(
+        ImmutableTable.of(CC, new Account.Id(2), ts)));
   }
 
   @Test