diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index ce7adc2..7ed0e17 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -773,10 +773,11 @@
 +
 Default is 128 MiB per cache, except:
 +
+* `"change_notes"`: disk storage is disabled by default
 * `"diff_summary"`: default is `1g` (1 GiB of disk space)
 
 +
-If 0, disk storage for the cache is disabled.
+If 0 or negative, disk storage for the cache is disabled.
 
 ==== [[cache_names]]Standard Caches
 
diff --git a/WORKSPACE b/WORKSPACE
index 15d8651..94138e4 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -711,6 +711,18 @@
     sha1 = "636e49d675bc28e0b3ae0edd077d6acbbb159166",
 )
 
+maven_jar(
+    name = "truth-liteproto-extension",
+    artifact = "com.google.truth.extensions:truth-liteproto-extension:" + TRUTH_VERS,
+    sha1 = "21210ac07e5cfbe83f04733f806224a6c0ae4d2d",
+)
+
+maven_jar(
+    name = "truth-proto-extension",
+    artifact = "com.google.truth.extensions:truth-proto-extension:" + TRUTH_VERS,
+    sha1 = "5a2b504143a5fec2b6be8bce292b3b7577a81789",
+)
+
 # When bumping the easymock version number, make sure to also move powermock to a compatible version
 maven_jar(
     name = "easymock",
diff --git a/contrib/populate-fixture-data.py b/contrib/populate-fixture-data.py
index 93ac34f..e7e8d0b 100755
--- a/contrib/populate-fixture-data.py
+++ b/contrib/populate-fixture-data.py
@@ -160,7 +160,7 @@
 def generate_random_text():
   return " ".join([random.choice("lorem ipsum "
                                  "doleret delendam "
-                                 "\n esse".split(" ")) for _ in xrange(1, 100)])
+                                 "\n esse".split(" ")) for _ in range(1, 100)])
 
 
 def set_up():
@@ -299,7 +299,7 @@
   project_names = create_gerrit_projects(group_names)
 
   for idx, u in enumerate(gerrit_users):
-    for _ in xrange(random.randint(1, 5)):
+    for _ in range(random.randint(1, 5)):
       create_change(u, project_names[4 * idx / len(gerrit_users)])
 
 main()
diff --git a/java/com/google/gerrit/reviewdb/server/ReviewDbCodecs.java b/java/com/google/gerrit/reviewdb/server/ReviewDbCodecs.java
index 631e7f5..2958464 100644
--- a/java/com/google/gerrit/reviewdb/server/ReviewDbCodecs.java
+++ b/java/com/google/gerrit/reviewdb/server/ReviewDbCodecs.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.reviewdb.server;
 
 import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.ChangeMessage;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gwtorm.protobuf.CodecFactory;
@@ -27,6 +28,9 @@
 
   public static final ProtobufCodec<Change> CHANGE_CODEC = CodecFactory.encoder(Change.class);
 
+  public static final ProtobufCodec<ChangeMessage> MESSAGE_CODEC =
+      CodecFactory.encoder(ChangeMessage.class);
+
   public static final ProtobufCodec<PatchSet> PATCH_SET_CODEC =
       CodecFactory.encoder(PatchSet.class);
 
diff --git a/java/com/google/gerrit/server/account/AccountsUpdate.java b/java/com/google/gerrit/server/account/AccountsUpdate.java
index 2f36cf2..996e602 100644
--- a/java/com/google/gerrit/server/account/AccountsUpdate.java
+++ b/java/com/google/gerrit/server/account/AccountsUpdate.java
@@ -106,7 +106,8 @@
  *   <li>binding {@link GitReferenceUpdated#DISABLED} and
  *   <li>passing an {@link
  *       com.google.gerrit.server.account.externalids.ExternalIdNotes.FactoryNoReindex} factory as
- *       parameter of {@link AccountsUpdate.Factory#create(IdentifiedUser, ExternalIdNotesLoader)}
+ *       parameter of {@link AccountsUpdate.Factory#create(IdentifiedUser,
+ *       ExternalIdNotes.ExternalIdNotesLoader)}
  * </ul>
  *
  * <p>If there are concurrent account updates updating the user branch in NoteDb may fail with
diff --git a/java/com/google/gerrit/server/cache/PersistentCacheBinding.java b/java/com/google/gerrit/server/cache/PersistentCacheBinding.java
index 429f5ab..794d3bb 100644
--- a/java/com/google/gerrit/server/cache/PersistentCacheBinding.java
+++ b/java/com/google/gerrit/server/cache/PersistentCacheBinding.java
@@ -34,7 +34,12 @@
 
   PersistentCacheBinding<K, V> version(int version);
 
-  /** Set the total on-disk limit of the cache */
+  /**
+   * Set the total on-disk limit of the cache.
+   *
+   * <p>If 0 or negative, persistence for the cache is disabled by default, but may still be
+   * overridden in the config.
+   */
   PersistentCacheBinding<K, V> diskLimit(long limit);
 
   PersistentCacheBinding<K, V> keySerializer(CacheSerializer<K> keySerializer);
diff --git a/java/com/google/gerrit/server/cache/PersistentCacheProvider.java b/java/com/google/gerrit/server/cache/PersistentCacheProvider.java
index 405de4f..46a9e61 100644
--- a/java/com/google/gerrit/server/cache/PersistentCacheProvider.java
+++ b/java/com/google/gerrit/server/cache/PersistentCacheProvider.java
@@ -39,6 +39,7 @@
       CacheModule module, String name, TypeLiteral<K> keyType, TypeLiteral<V> valType) {
     super(module, name, keyType, valType);
     version = -1;
+    diskLimit = 128 << 20;
   }
 
   @Inject(optional = true)
@@ -93,10 +94,7 @@
 
   @Override
   public long diskLimit() {
-    if (diskLimit > 0) {
-      return diskLimit;
-    }
-    return 128 << 20;
+    return diskLimit;
   }
 
   @Override
diff --git a/java/com/google/gerrit/server/cache/ProtoCacheSerializers.java b/java/com/google/gerrit/server/cache/ProtoCacheSerializers.java
index 795df72..9fe6b83 100644
--- a/java/com/google/gerrit/server/cache/ProtoCacheSerializers.java
+++ b/java/com/google/gerrit/server/cache/ProtoCacheSerializers.java
@@ -14,6 +14,8 @@
 
 package com.google.gerrit.server.cache;
 
+import com.google.gwtorm.protobuf.ProtobufCodec;
+import com.google.protobuf.ByteString;
 import com.google.protobuf.CodedOutputStream;
 import com.google.protobuf.MessageLite;
 import java.io.IOException;
@@ -23,8 +25,8 @@
   /**
    * Serializes a proto to a byte array.
    *
-   * <p>Guarantees deterministic serialization and thus is suitable for use as a persistent cache
-   * key. Should be used in preference to {@link MessageLite#toByteArray()}, which is not guaranteed
+   * <p>Guarantees deterministic serialization and thus is suitable for use in persistent caches.
+   * Should be used in preference to {@link MessageLite#toByteArray()}, which is not guaranteed
    * deterministic.
    *
    * @param message the proto message to serialize.
@@ -39,7 +41,30 @@
       cout.checkNoSpaceLeft();
       return bytes;
     } catch (IOException e) {
-      throw new IllegalStateException("exception writing to byte array");
+      throw new IllegalStateException("exception writing to byte array", e);
+    }
+  }
+
+  /**
+   * Serializes an object to a {@link ByteString} using a protobuf codec.
+   *
+   * <p>Guarantees deterministic serialization and thus is suitable for use in persistent caches.
+   * Should be used in preference to {@link ProtobufCodec#encodeToByteString(Object)}, which is not
+   * guaranteed deterministic.
+   *
+   * @param object the object to serialize.
+   * @param codec codec for serializing.
+   * @return a {@code ByteString} with the message contents.
+   */
+  public static <T> ByteString toByteString(T object, ProtobufCodec<T> codec) {
+    try (ByteString.Output bout = ByteString.newOutput()) {
+      CodedOutputStream cout = CodedOutputStream.newInstance(bout);
+      cout.useDeterministicSerialization();
+      codec.encode(object, cout);
+      cout.flush();
+      return bout.toByteString();
+    } catch (IOException e) {
+      throw new IllegalStateException("exception writing to ByteString", e);
     }
   }
 
diff --git a/java/com/google/gerrit/server/cache/testing/SerializedClassSubject.java b/java/com/google/gerrit/server/cache/testing/SerializedClassSubject.java
index 78900cb..19c5b67 100644
--- a/java/com/google/gerrit/server/cache/testing/SerializedClassSubject.java
+++ b/java/com/google/gerrit/server/cache/testing/SerializedClassSubject.java
@@ -22,8 +22,10 @@
 import com.google.common.truth.FailureMetadata;
 import com.google.common.truth.Subject;
 import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Type;
+import java.util.Arrays;
 import java.util.Map;
 import org.apache.commons.lang3.reflect.FieldUtils;
 
@@ -62,6 +64,13 @@
     super(metadata, actual);
   }
 
+  public void isAbstract() {
+    isNotNull();
+    assertWithMessage("expected class %s to be abstract", actual().getName())
+        .that(Modifier.isAbstract(actual().getModifiers()))
+        .isTrue();
+  }
+
   public void isConcrete() {
     isNotNull();
     assertWithMessage("expected class %s to be concrete", actual().getName())
@@ -78,4 +87,17 @@
                 .collect(toImmutableMap(Field::getName, Field::getGenericType)))
         .containsExactlyEntriesIn(expectedFields);
   }
+
+  public void hasAutoValueMethods(Map<String, Type> expectedMethods) {
+    // Would be nice if we could check clazz is an @AutoValue, but the retention is not RUNTIME.
+    isAbstract();
+    assertThat(
+            Arrays.stream(actual().getDeclaredMethods())
+                .filter(m -> !Modifier.isStatic(m.getModifiers()))
+                .filter(m -> Modifier.isAbstract(m.getModifiers()))
+                .filter(m -> m.getParameters().length == 0)
+                .collect(toImmutableMap(Method::getName, Method::getGenericReturnType)))
+        .named("no-argument abstract methods on %s", actual().getName())
+        .isEqualTo(expectedMethods);
+  }
 }
diff --git a/java/com/google/gerrit/server/group/db/InternalGroupUpdate.java b/java/com/google/gerrit/server/group/db/InternalGroupUpdate.java
index 5ce3c1c..bff2952 100644
--- a/java/com/google/gerrit/server/group/db/InternalGroupUpdate.java
+++ b/java/com/google/gerrit/server/group/db/InternalGroupUpdate.java
@@ -142,8 +142,8 @@
      * InternalGroupUpdate}.
      *
      * <p>This modification can be tweaked further and passed to {@link
-     * #setMemberModification(MemberModification)} in order to combine multiple member additions,
-     * deletions, or other modifications into one update.
+     * #setMemberModification(InternalGroupUpdate.MemberModification)} in order to combine multiple
+     * member additions, deletions, or other modifications into one update.
      */
     public abstract MemberModification getMemberModification();
 
@@ -155,8 +155,8 @@
      * InternalGroupUpdate}.
      *
      * <p>This modification can be tweaked further and passed to {@link
-     * #setSubgroupModification(SubgroupModification)} in order to combine multiple subgroup
-     * additions, deletions, or other modifications into one update.
+     * #setSubgroupModification(InternalGroupUpdate.SubgroupModification)} in order to combine
+     * multiple subgroup additions, deletions, or other modifications into one update.
      */
     public abstract SubgroupModification getSubgroupModification();
 
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index 5db347e..82253f2 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -643,7 +643,7 @@
    * <p>Stored fields need to use a stable format over a long period; this type insulates the index
    * from implementation changes in SubmitRecord itself.
    */
-  static class StoredSubmitRecord {
+  public static class StoredSubmitRecord {
     static class StoredLabel {
       String label;
       SubmitRecord.Label.Status status;
@@ -661,7 +661,7 @@
     List<StoredRequirement> requirements;
     String errorMessage;
 
-    StoredSubmitRecord(SubmitRecord rec) {
+    public StoredSubmitRecord(SubmitRecord rec) {
       this.status = rec.status;
       this.errorMessage = rec.errorMessage;
       if (rec.labels != null) {
@@ -686,7 +686,7 @@
       }
     }
 
-    private SubmitRecord toSubmitRecord() {
+    public SubmitRecord toSubmitRecord() {
       SubmitRecord rec = new SubmitRecord();
       rec.status = status;
       rec.errorMessage = errorMessage;
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotesCache.java b/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
index 5658569..d1c28c4 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
@@ -25,12 +25,16 @@
 import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.cache.CacheModule;
+import com.google.gerrit.server.cache.CacheSerializer;
+import com.google.gerrit.server.cache.ProtoCacheSerializers;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesKeyProto;
 import com.google.gerrit.server.notedb.AbstractChangeNotes.Args;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
 import com.google.inject.Inject;
 import com.google.inject.Module;
 import com.google.inject.Singleton;
 import com.google.inject.name.Named;
+import com.google.protobuf.ByteString;
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
@@ -38,6 +42,7 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 
 @Singleton
@@ -49,20 +54,59 @@
       @Override
       protected void configure() {
         bind(ChangeNotesCache.class);
-        cache(CACHE_NAME, Key.class, ChangeNotesState.class)
+        persist(CACHE_NAME, Key.class, ChangeNotesState.class)
             .weigher(Weigher.class)
-            .maximumWeight(10 << 20);
+            .maximumWeight(10 << 20)
+            .diskLimit(-1)
+            .version(1)
+            .keySerializer(Key.Serializer.INSTANCE)
+            .valueSerializer(ChangeNotesState.Serializer.INSTANCE);
       }
     };
   }
 
   @AutoValue
   public abstract static class Key {
+    static Key create(Project.NameKey project, Change.Id changeId, ObjectId id) {
+      return new AutoValue_ChangeNotesCache_Key(project, changeId, id.copy());
+    }
+
     abstract Project.NameKey project();
 
     abstract Change.Id changeId();
 
     abstract ObjectId id();
+
+    @VisibleForTesting
+    static enum Serializer implements CacheSerializer<Key> {
+      INSTANCE;
+
+      @Override
+      public byte[] serialize(Key object) {
+        byte[] buf = new byte[Constants.OBJECT_ID_LENGTH];
+        object.id().copyRawTo(buf, 0);
+        return ProtoCacheSerializers.toByteArray(
+            ChangeNotesKeyProto.newBuilder()
+                .setProject(object.project().get())
+                .setChangeId(object.changeId().get())
+                .setId(ByteString.copyFrom(buf))
+                .build());
+      }
+
+      @Override
+      public Key deserialize(byte[] in) {
+        ChangeNotesKeyProto proto;
+        try {
+          proto = ChangeNotesKeyProto.parseFrom(in);
+        } catch (IOException e) {
+          throw new IllegalArgumentException("Failed to deserialize " + Key.class.getName());
+        }
+        return Key.create(
+            new Project.NameKey(proto.getProject()),
+            new Change.Id(proto.getChangeId()),
+            ObjectId.fromRaw(proto.getId().toByteArray()));
+      }
+    }
   }
 
   public static class Weigher implements com.google.common.cache.Weigher<Key, ChangeNotesState> {
@@ -134,7 +178,7 @@
           + T // readOnlyUntil
           + 1 // isPrivate
           + 1 // workInProgress
-          + 1; // hasReviewStarted
+          + 1; // reviewStarted
     }
 
     private static int ptr(Object o, int size) {
@@ -330,7 +374,7 @@
   Value get(Project.NameKey project, Change.Id changeId, ObjectId metaId, ChangeNotesRevWalk rw)
       throws IOException {
     try {
-      Key key = new AutoValue_ChangeNotesCache_Key(project, changeId, metaId.copy());
+      Key key = Key.create(project, changeId, metaId);
       Loader loader = new Loader(key, rw);
       ChangeNotesState s = cache.get(key, loader);
       return new AutoValue_ChangeNotesCache_Value(s, loader.revisionNoteMap);
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotesState.java b/java/com/google/gerrit/server/notedb/ChangeNotesState.java
index 78734f9..1b09494 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotesState.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotesState.java
@@ -14,15 +14,29 @@
 
 package com.google.gerrit.server.notedb;
 
+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.common.collect.ImmutableList.toImmutableList;
+import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.APPROVAL_CODEC;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.MESSAGE_CODEC;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.PATCH_SET_CODEC;
+import static com.google.gerrit.server.cache.ProtoCacheSerializers.toByteString;
 
 import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Converter;
+import com.google.common.base.Enums;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
 import com.google.common.collect.ListMultimap;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Table;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.data.SubmitRecord;
 import com.google.gerrit.reviewdb.client.Account;
@@ -34,15 +48,28 @@
 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.OutputFormat;
 import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
+import com.google.gerrit.server.cache.CacheSerializer;
+import com.google.gerrit.server.cache.ProtoCacheSerializers;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ChangeColumnsProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerByEmailSetEntryProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerSetEntryProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerStatusUpdateProto;
+import com.google.gerrit.server.index.change.ChangeField.StoredSubmitRecord;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.notedb.NoteDbChangeState.PrimaryStorage;
+import com.google.gson.Gson;
+import com.google.protobuf.ByteString;
 import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 
 /**
@@ -95,7 +122,7 @@
       @Nullable Timestamp readOnlyUntil,
       boolean isPrivate,
       boolean workInProgress,
-      boolean hasReviewStarted,
+      boolean reviewStarted,
       @Nullable Change.Id revertOf) {
     checkNotNull(
         metaId,
@@ -106,22 +133,22 @@
         .metaId(metaId)
         .changeId(changeId)
         .columns(
-            new AutoValue_ChangeNotesState_ChangeColumns.Builder()
+            ChangeColumns.builder()
                 .changeKey(changeKey)
                 .createdOn(createdOn)
                 .lastUpdatedOn(lastUpdatedOn)
                 .owner(owner)
                 .branch(branch)
+                .status(status)
                 .currentPatchSetId(currentPatchSetId)
                 .subject(subject)
                 .topic(topic)
                 .originalSubject(originalSubject)
                 .submissionId(submissionId)
                 .assignee(assignee)
-                .status(status)
                 .isPrivate(isPrivate)
-                .isWorkInProgress(workInProgress)
-                .hasReviewStarted(hasReviewStarted)
+                .workInProgress(workInProgress)
+                .reviewStarted(reviewStarted)
                 .revertOf(revertOf)
                 .build())
         .pastAssignees(pastAssignees)
@@ -147,10 +174,14 @@
    * <p>Notable exceptions include rowVersion and noteDbState, which are only make sense when read
    * from NoteDb, so they cannot be cached.
    *
-   * <p>Fields are in listed column order.
+   * <p>Fields should match the column names in {@link Change}, and are in listed column order.
    */
   @AutoValue
   abstract static class ChangeColumns {
+    static Builder builder() {
+      return new AutoValue_ChangeNotesState_ChangeColumns.Builder();
+    }
+
     abstract Change.Key changeKey();
 
     abstract Timestamp createdOn();
@@ -162,6 +193,10 @@
     // Project not included, as it's not stored anywhere in the meta ref.
     abstract String branch();
 
+    // TODO(dborowitz): Use a sensible default other than null
+    @Nullable
+    abstract Change.Status status();
+
     @Nullable
     abstract PatchSet.Id currentPatchSetId();
 
@@ -178,19 +213,18 @@
 
     @Nullable
     abstract Account.Id assignee();
-    // TODO(dborowitz): Use a sensible default other than null
-    @Nullable
-    abstract Change.Status status();
 
     abstract boolean isPrivate();
 
-    abstract boolean isWorkInProgress();
+    abstract boolean workInProgress();
 
-    abstract boolean hasReviewStarted();
+    abstract boolean reviewStarted();
 
     @Nullable
     abstract Change.Id revertOf();
 
+    abstract Builder toBuilder();
+
     @AutoValue.Builder
     abstract static class Builder {
       abstract Builder changeKey(Change.Key changeKey);
@@ -219,9 +253,9 @@
 
       abstract Builder isPrivate(boolean isPrivate);
 
-      abstract Builder isWorkInProgress(boolean isWorkInProgress);
+      abstract Builder workInProgress(boolean workInProgress);
 
-      abstract Builder hasReviewStarted(boolean hasReviewStarted);
+      abstract Builder reviewStarted(boolean reviewStarted);
 
       abstract Builder revertOf(@Nullable Change.Id revertOf);
 
@@ -327,8 +361,8 @@
     change.setSubmissionId(c.submissionId());
     change.setAssignee(c.assignee());
     change.setPrivate(c.isPrivate());
-    change.setWorkInProgress(c.isWorkInProgress());
-    change.setReviewStarted(c.hasReviewStarted());
+    change.setWorkInProgress(c.workInProgress());
+    change.setReviewStarted(c.reviewStarted());
     change.setRevertOf(c.revertOf());
 
     if (!patchSets().isEmpty()) {
@@ -368,7 +402,7 @@
 
     abstract Builder pastAssignees(Set<Account.Id> pastAssignees);
 
-    abstract Builder hashtags(Set<String> hashtags);
+    abstract Builder hashtags(Iterable<String> hashtags);
 
     abstract Builder patchSets(Iterable<Map.Entry<PatchSet.Id, PatchSet>> patchSets);
 
@@ -396,4 +430,274 @@
 
     abstract ChangeNotesState build();
   }
+
+  static enum Serializer implements CacheSerializer<ChangeNotesState> {
+    INSTANCE;
+
+    @VisibleForTesting static final Gson GSON = OutputFormat.JSON_COMPACT.newGson();
+
+    private static final Converter<String, Change.Status> STATUS_CONVERTER =
+        Enums.stringConverter(Change.Status.class);
+    private static final Converter<String, ReviewerStateInternal> REVIEWER_STATE_CONVERTER =
+        Enums.stringConverter(ReviewerStateInternal.class);
+
+    @Override
+    public byte[] serialize(ChangeNotesState object) {
+      checkArgument(object.metaId() != null, "meta ID is required in: %s", object);
+      checkArgument(object.columns() != null, "ChangeColumns is required in: %s", object);
+      ChangeNotesStateProto.Builder b = ChangeNotesStateProto.newBuilder();
+
+      byte[] idBuf = new byte[Constants.OBJECT_ID_LENGTH];
+      object.metaId().copyRawTo(idBuf, 0);
+      b.setMetaId(ByteString.copyFrom(idBuf))
+          .setChangeId(object.changeId().get())
+          .setColumns(toChangeColumnsProto(object.columns()));
+
+      object.pastAssignees().forEach(a -> b.addPastAssignee(a.get()));
+      object.hashtags().forEach(b::addHashtag);
+      object.patchSets().forEach(e -> b.addPatchSet(toByteString(e.getValue(), PATCH_SET_CODEC)));
+      object.approvals().forEach(e -> b.addApproval(toByteString(e.getValue(), APPROVAL_CODEC)));
+
+      object.reviewers().asTable().cellSet().forEach(c -> b.addReviewer(toReviewerSetEntry(c)));
+      object
+          .reviewersByEmail()
+          .asTable()
+          .cellSet()
+          .forEach(c -> b.addReviewerByEmail(toReviewerByEmailSetEntry(c)));
+      object
+          .pendingReviewers()
+          .asTable()
+          .cellSet()
+          .forEach(c -> b.addPendingReviewer(toReviewerSetEntry(c)));
+      object
+          .pendingReviewersByEmail()
+          .asTable()
+          .cellSet()
+          .forEach(c -> b.addPendingReviewerByEmail(toReviewerByEmailSetEntry(c)));
+
+      object.allPastReviewers().forEach(a -> b.addPastReviewer(a.get()));
+      object.reviewerUpdates().forEach(u -> b.addReviewerUpdate(toReviewerStatusUpdateProto(u)));
+      object
+          .submitRecords()
+          .forEach(r -> b.addSubmitRecord(GSON.toJson(new StoredSubmitRecord(r))));
+      object.changeMessages().forEach(m -> b.addChangeMessage(toByteString(m, MESSAGE_CODEC)));
+      object.publishedComments().values().forEach(c -> b.addPublishedComment(GSON.toJson(c)));
+
+      if (object.readOnlyUntil() != null) {
+        b.setReadOnlyUntil(object.readOnlyUntil().getTime()).setHasReadOnlyUntil(true);
+      }
+
+      return ProtoCacheSerializers.toByteArray(b.build());
+    }
+
+    private static ChangeColumnsProto toChangeColumnsProto(ChangeColumns cols) {
+      ChangeColumnsProto.Builder b =
+          ChangeColumnsProto.newBuilder()
+              .setChangeKey(cols.changeKey().get())
+              .setCreatedOn(cols.createdOn().getTime())
+              .setLastUpdatedOn(cols.lastUpdatedOn().getTime())
+              .setOwner(cols.owner().get())
+              .setBranch(cols.branch());
+      if (cols.currentPatchSetId() != null) {
+        b.setCurrentPatchSetId(cols.currentPatchSetId().get()).setHasCurrentPatchSetId(true);
+      }
+      b.setSubject(cols.subject());
+      if (cols.topic() != null) {
+        b.setTopic(cols.topic()).setHasTopic(true);
+      }
+      if (cols.originalSubject() != null) {
+        b.setOriginalSubject(cols.originalSubject()).setHasOriginalSubject(true);
+      }
+      if (cols.submissionId() != null) {
+        b.setSubmissionId(cols.submissionId()).setHasSubmissionId(true);
+      }
+      if (cols.assignee() != null) {
+        b.setAssignee(cols.assignee().get()).setHasAssignee(true);
+      }
+      if (cols.status() != null) {
+        b.setStatus(STATUS_CONVERTER.reverse().convert(cols.status())).setHasStatus(true);
+      }
+      b.setIsPrivate(cols.isPrivate())
+          .setWorkInProgress(cols.workInProgress())
+          .setReviewStarted(cols.reviewStarted());
+      if (cols.revertOf() != null) {
+        b.setRevertOf(cols.revertOf().get()).setHasRevertOf(true);
+      }
+      return b.build();
+    }
+
+    private static ReviewerSetEntryProto toReviewerSetEntry(
+        Table.Cell<ReviewerStateInternal, Account.Id, Timestamp> c) {
+      return ReviewerSetEntryProto.newBuilder()
+          .setState(REVIEWER_STATE_CONVERTER.reverse().convert(c.getRowKey()))
+          .setAccountId(c.getColumnKey().get())
+          .setTimestamp(c.getValue().getTime())
+          .build();
+    }
+
+    private static ReviewerByEmailSetEntryProto toReviewerByEmailSetEntry(
+        Table.Cell<ReviewerStateInternal, Address, Timestamp> c) {
+      return ReviewerByEmailSetEntryProto.newBuilder()
+          .setState(REVIEWER_STATE_CONVERTER.reverse().convert(c.getRowKey()))
+          .setAddress(c.getColumnKey().toHeaderString())
+          .setTimestamp(c.getValue().getTime())
+          .build();
+    }
+
+    private static ReviewerStatusUpdateProto toReviewerStatusUpdateProto(ReviewerStatusUpdate u) {
+      return ReviewerStatusUpdateProto.newBuilder()
+          .setDate(u.date().getTime())
+          .setUpdatedBy(u.updatedBy().get())
+          .setReviewer(u.reviewer().get())
+          .setState(REVIEWER_STATE_CONVERTER.reverse().convert(u.state()))
+          .build();
+    }
+
+    @Override
+    public ChangeNotesState deserialize(byte[] in) {
+      ChangeNotesStateProto proto;
+      try {
+        proto = ChangeNotesStateProto.parseFrom(in);
+      } catch (IOException e) {
+        throw new IllegalArgumentException(
+            "Failed to deserialize " + ChangeNotesState.class.getName());
+      }
+      Change.Id changeId = new Change.Id(proto.getChangeId());
+
+      ChangeNotesState.Builder b =
+          builder()
+              .metaId(ObjectId.fromRaw(proto.getMetaId().toByteArray()))
+              .changeId(changeId)
+              .columns(toChangeColumns(changeId, proto.getColumns()))
+              .pastAssignees(
+                  proto
+                      .getPastAssigneeList()
+                      .stream()
+                      .map(Account.Id::new)
+                      .collect(toImmutableSet()))
+              .hashtags(proto.getHashtagList())
+              .patchSets(
+                  proto
+                      .getPatchSetList()
+                      .stream()
+                      .map(PATCH_SET_CODEC::decode)
+                      .map(ps -> Maps.immutableEntry(ps.getId(), ps))
+                      .collect(toImmutableList()))
+              .approvals(
+                  proto
+                      .getApprovalList()
+                      .stream()
+                      .map(APPROVAL_CODEC::decode)
+                      .map(a -> Maps.immutableEntry(a.getPatchSetId(), a))
+                      .collect(toImmutableList()))
+              .reviewers(toReviewerSet(proto.getReviewerList()))
+              .reviewersByEmail(toReviewerByEmailSet(proto.getReviewerByEmailList()))
+              .pendingReviewers(toReviewerSet(proto.getPendingReviewerList()))
+              .pendingReviewersByEmail(toReviewerByEmailSet(proto.getPendingReviewerByEmailList()))
+              .allPastReviewers(
+                  proto
+                      .getPastReviewerList()
+                      .stream()
+                      .map(Account.Id::new)
+                      .collect(toImmutableList()))
+              .reviewerUpdates(toReviewerStatusUpdateList(proto.getReviewerUpdateList()))
+              .submitRecords(
+                  proto
+                      .getSubmitRecordList()
+                      .stream()
+                      .map(r -> GSON.fromJson(r, StoredSubmitRecord.class).toSubmitRecord())
+                      .collect(toImmutableList()))
+              .changeMessages(
+                  proto
+                      .getChangeMessageList()
+                      .stream()
+                      .map(MESSAGE_CODEC::decode)
+                      .collect(toImmutableList()))
+              .publishedComments(
+                  proto
+                      .getPublishedCommentList()
+                      .stream()
+                      .map(r -> GSON.fromJson(r, Comment.class))
+                      .collect(toImmutableListMultimap(c -> new RevId(c.revId), c -> c)));
+      if (proto.getHasReadOnlyUntil()) {
+        b.readOnlyUntil(new Timestamp(proto.getReadOnlyUntil()));
+      }
+      return b.build();
+    }
+
+    private static ChangeColumns toChangeColumns(Change.Id changeId, ChangeColumnsProto proto) {
+      ChangeColumns.Builder b =
+          ChangeColumns.builder()
+              .changeKey(new Change.Key(proto.getChangeKey()))
+              .createdOn(new Timestamp(proto.getCreatedOn()))
+              .lastUpdatedOn(new Timestamp(proto.getLastUpdatedOn()))
+              .owner(new Account.Id(proto.getOwner()))
+              .branch(proto.getBranch());
+      if (proto.getHasCurrentPatchSetId()) {
+        b.currentPatchSetId(new PatchSet.Id(changeId, proto.getCurrentPatchSetId()));
+      }
+      b.subject(proto.getSubject());
+      if (proto.getHasTopic()) {
+        b.topic(proto.getTopic());
+      }
+      if (proto.getHasOriginalSubject()) {
+        b.originalSubject(proto.getOriginalSubject());
+      }
+      if (proto.getHasSubmissionId()) {
+        b.submissionId(proto.getSubmissionId());
+      }
+      if (proto.getHasAssignee()) {
+        b.assignee(new Account.Id(proto.getAssignee()));
+      }
+      if (proto.getHasStatus()) {
+        b.status(STATUS_CONVERTER.convert(proto.getStatus()));
+      }
+      b.isPrivate(proto.getIsPrivate())
+          .workInProgress(proto.getWorkInProgress())
+          .reviewStarted(proto.getReviewStarted());
+      if (proto.getHasRevertOf()) {
+        b.revertOf(new Change.Id(proto.getRevertOf()));
+      }
+      return b.build();
+    }
+
+    private static ReviewerSet toReviewerSet(List<ReviewerSetEntryProto> protos) {
+      ImmutableTable.Builder<ReviewerStateInternal, Account.Id, Timestamp> b =
+          ImmutableTable.builder();
+      for (ReviewerSetEntryProto e : protos) {
+        b.put(
+            REVIEWER_STATE_CONVERTER.convert(e.getState()),
+            new Account.Id(e.getAccountId()),
+            new Timestamp(e.getTimestamp()));
+      }
+      return ReviewerSet.fromTable(b.build());
+    }
+
+    private static ReviewerByEmailSet toReviewerByEmailSet(
+        List<ReviewerByEmailSetEntryProto> protos) {
+      ImmutableTable.Builder<ReviewerStateInternal, Address, Timestamp> b =
+          ImmutableTable.builder();
+      for (ReviewerByEmailSetEntryProto e : protos) {
+        b.put(
+            REVIEWER_STATE_CONVERTER.convert(e.getState()),
+            Address.parse(e.getAddress()),
+            new Timestamp(e.getTimestamp()));
+      }
+      return ReviewerByEmailSet.fromTable(b.build());
+    }
+
+    private static ImmutableList<ReviewerStatusUpdate> toReviewerStatusUpdateList(
+        List<ReviewerStatusUpdateProto> protos) {
+      ImmutableList.Builder<ReviewerStatusUpdate> b = ImmutableList.builder();
+      for (ReviewerStatusUpdateProto proto : protos) {
+        b.add(
+            ReviewerStatusUpdate.create(
+                new Timestamp(proto.getDate()),
+                new Account.Id(proto.getUpdatedBy()),
+                new Account.Id(proto.getReviewer()),
+                REVIEWER_STATE_CONVERTER.convert(proto.getState())));
+      }
+      return b.build();
+    }
+  }
 }
diff --git a/javatests/com/google/gerrit/server/BUILD b/javatests/com/google/gerrit/server/BUILD
index 1b11dd65..3113a8a 100644
--- a/javatests/com/google/gerrit/server/BUILD
+++ b/javatests/com/google/gerrit/server/BUILD
@@ -65,6 +65,7 @@
         "//lib/jgit/org.eclipse.jgit.junit:junit",
         "//lib/truth",
         "//lib/truth:truth-java8-extension",
+        "//lib/truth:truth-proto-extension",
         "//proto:cache_java_proto",
     ],
 )
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesCacheTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesCacheTest.java
new file mode 100644
index 0000000..5a7d812
--- /dev/null
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesCacheTest.java
@@ -0,0 +1,60 @@
+// Copyright (C) 2018 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;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.extensions.proto.ProtoTruth.assertThat;
+import static com.google.gerrit.server.cache.testing.CacheSerializerTestUtil.bytes;
+import static com.google.gerrit.server.cache.testing.SerializedClassSubject.assertThatSerializedClass;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesKeyProto;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
+
+public final class ChangeNotesCacheTest {
+  @Test
+  public void keySerializer() throws Exception {
+    ChangeNotesCache.Key key =
+        ChangeNotesCache.Key.create(
+            new Project.NameKey("project"),
+            new Change.Id(1234),
+            ObjectId.fromString("deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"));
+    byte[] serialized = ChangeNotesCache.Key.Serializer.INSTANCE.serialize(key);
+    assertThat(ChangeNotesKeyProto.parseFrom(serialized))
+        .isEqualTo(
+            ChangeNotesKeyProto.newBuilder()
+                .setProject("project")
+                .setChangeId(1234)
+                .setId(
+                    bytes(
+                        0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef,
+                        0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef))
+                .build());
+    assertThat(ChangeNotesCache.Key.Serializer.INSTANCE.deserialize(serialized)).isEqualTo(key);
+  }
+
+  @Test
+  public void keyMethods() throws Exception {
+    assertThatSerializedClass(ChangeNotesCache.Key.class)
+        .hasAutoValueMethods(
+            ImmutableMap.of(
+                "project", Project.NameKey.class,
+                "changeId", Change.Id.class,
+                "id", ObjectId.class));
+  }
+}
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
index d974877..b8f544a 100644
--- a/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
@@ -442,17 +442,17 @@
     // Change created in WIP remains in WIP.
     RevCommit commit = writeCommit("Update WIP change\n" + "\n" + "Patch-set: 1\n", true);
     ChangeNotesState state = newParser(commit).parseAll();
-    assertThat(state.columns().hasReviewStarted()).isFalse();
+    assertThat(state.columns().reviewStarted()).isFalse();
 
     // Moving change out of WIP starts review.
     commit =
         writeCommit("New ready change\n" + "\n" + "Patch-set: 1\n" + "Work-in-progress: false\n");
     state = newParser(commit).parseAll();
-    assertThat(state.columns().hasReviewStarted()).isTrue();
+    assertThat(state.columns().reviewStarted()).isTrue();
 
     // Change created not in WIP has always been in review started state.
     state = assertParseSucceeds("New change that doesn't declare WIP\n" + "\n" + "Patch-set: 1\n");
-    assertThat(state.columns().hasReviewStarted()).isTrue();
+    assertThat(state.columns().reviewStarted()).isTrue();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesStateTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesStateTest.java
new file mode 100644
index 0000000..c0f2c43
--- /dev/null
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesStateTest.java
@@ -0,0 +1,957 @@
+// Copyright (C) 2018 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;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.extensions.proto.ProtoTruth.assertThat;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.APPROVAL_CODEC;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.MESSAGE_CODEC;
+import static com.google.gerrit.reviewdb.server.ReviewDbCodecs.PATCH_SET_CODEC;
+import static com.google.gerrit.server.cache.testing.SerializedClassSubject.assertThatSerializedClass;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Iterables;
+import com.google.gerrit.common.data.SubmitRecord;
+import com.google.gerrit.common.data.SubmitRequirement;
+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.Comment;
+import com.google.gerrit.reviewdb.client.LabelId;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.reviewdb.client.RevId;
+import com.google.gerrit.server.ReviewerByEmailSet;
+import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.ReviewerStatusUpdate;
+import com.google.gerrit.server.cache.ProtoCacheSerializers;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ChangeColumnsProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerByEmailSetEntryProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerSetEntryProto;
+import com.google.gerrit.server.cache.proto.Cache.ChangeNotesStateProto.ReviewerStatusUpdateProto;
+import com.google.gerrit.server.mail.Address;
+import com.google.gerrit.server.notedb.ChangeNotesState.ChangeColumns;
+import com.google.gerrit.server.notedb.ChangeNotesState.Serializer;
+import com.google.gwtorm.client.KeyUtil;
+import com.google.gwtorm.protobuf.ProtobufCodec;
+import com.google.gwtorm.server.StandardKeyEncoder;
+import com.google.inject.TypeLiteral;
+import com.google.protobuf.ByteString;
+import java.lang.reflect.Type;
+import java.sql.Timestamp;
+import java.util.List;
+import java.util.Map;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Before;
+import org.junit.Test;
+
+public class ChangeNotesStateTest {
+  static {
+    KeyUtil.setEncoderImpl(new StandardKeyEncoder());
+  }
+
+  private static final Change.Id ID = new Change.Id(123);
+  private static final ObjectId SHA =
+      ObjectId.fromString("1234567812345678123456781234567812345678");
+  private static final ByteString SHA_BYTES = toByteString(SHA);
+  private static final String CHANGE_KEY = "Iabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd";
+
+  private ChangeColumns cols;
+  private ChangeColumnsProto colsProto;
+
+  @Before
+  public void setUp() throws Exception {
+    cols =
+        ChangeColumns.builder()
+            .changeKey(new Change.Key(CHANGE_KEY))
+            .createdOn(new Timestamp(123456L))
+            .lastUpdatedOn(new Timestamp(234567L))
+            .owner(new Account.Id(1000))
+            .branch("refs/heads/master")
+            .subject("Test change")
+            .isPrivate(false)
+            .workInProgress(false)
+            .reviewStarted(true)
+            .build();
+    colsProto = toProto(newBuilder().build()).getColumns();
+  }
+
+  private ChangeNotesState.Builder newBuilder() {
+    return ChangeNotesState.Builder.empty(ID).metaId(SHA).columns(cols);
+  }
+
+  @Test
+  public void serializeChangeKey() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .columns(
+                cols.toBuilder()
+                    .changeKey(new Change.Key("Ieeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"))
+                    .build())
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(
+                colsProto.toBuilder().setChangeKey("Ieeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"))
+            .build());
+  }
+
+  @Test
+  public void serializeCreatedOn() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().createdOn(new Timestamp(98765L)).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setCreatedOn(98765L))
+            .build());
+  }
+
+  @Test
+  public void serializeLastUpdatedOn() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().lastUpdatedOn(new Timestamp(98765L)).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setLastUpdatedOn(98765L))
+            .build());
+  }
+
+  @Test
+  public void serializeOwner() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().owner(new Account.Id(7777)).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setOwner(7777))
+            .build());
+  }
+
+  @Test
+  public void serializeBranch() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().branch("refs/heads/bar").build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setBranch("refs/heads/bar"))
+            .build());
+  }
+
+  @Test
+  public void serializeSubject() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().subject("A different test change").build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setSubject("A different test change"))
+            .build());
+  }
+
+  @Test
+  public void serializeCurrentPatchSetId() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .columns(cols.toBuilder().currentPatchSetId(new PatchSet.Id(ID, 2)).build())
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setCurrentPatchSetId(2).setHasCurrentPatchSetId(true))
+            .build());
+  }
+
+  @Test
+  public void serializeNullTopic() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().topic(null).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .build());
+  }
+
+  @Test
+  public void serializeEmptyTopic() throws Exception {
+    ChangeNotesState state = newBuilder().columns(cols.toBuilder().topic("").build()).build();
+    assertRoundTrip(
+        state,
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setTopic("").setHasTopic(true))
+            .build());
+  }
+
+  @Test
+  public void serializeNonEmptyTopic() throws Exception {
+    ChangeNotesState state = newBuilder().columns(cols.toBuilder().topic("topic").build()).build();
+    assertRoundTrip(
+        state,
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setTopic("topic").setHasTopic(true))
+            .build());
+  }
+
+  @Test
+  public void serializeOriginalSubject() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .columns(cols.toBuilder().originalSubject("The first patch set").build())
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(
+                colsProto
+                    .toBuilder()
+                    .setOriginalSubject("The first patch set")
+                    .setHasOriginalSubject(true))
+            .build());
+  }
+
+  @Test
+  public void serializeSubmissionId() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().submissionId("xyz").build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setSubmissionId("xyz").setHasSubmissionId(true))
+            .build());
+  }
+
+  @Test
+  public void serializeAssignee() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().assignee(new Account.Id(2000)).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setAssignee(2000).setHasAssignee(true))
+            .build());
+  }
+
+  @Test
+  public void serializeStatus() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().status(Change.Status.MERGED).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setStatus("MERGED").setHasStatus(true))
+            .build());
+  }
+
+  @Test
+  public void serializeIsPrivate() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().isPrivate(true).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setIsPrivate(true))
+            .build());
+  }
+
+  @Test
+  public void serializeIsWorkInProgress() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().workInProgress(true).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setWorkInProgress(true))
+            .build());
+  }
+
+  @Test
+  public void serializeHasReviewStarted() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().reviewStarted(true).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setReviewStarted(true))
+            .build());
+  }
+
+  @Test
+  public void serializeRevertOf() throws Exception {
+    assertRoundTrip(
+        newBuilder().columns(cols.toBuilder().revertOf(new Change.Id(999)).build()).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto.toBuilder().setRevertOf(999).setHasRevertOf(true))
+            .build());
+  }
+
+  @Test
+  public void serializePastAssignees() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .pastAssignees(ImmutableSet.of(new Account.Id(2002), new Account.Id(2001)))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPastAssignee(2002)
+            .addPastAssignee(2001)
+            .build());
+  }
+
+  @Test
+  public void serializeHashtags() throws Exception {
+    assertRoundTrip(
+        newBuilder().hashtags(ImmutableSet.of("tag2", "tag1")).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addHashtag("tag2")
+            .addHashtag("tag1")
+            .build());
+  }
+
+  @Test
+  public void serializePatchSets() throws Exception {
+    PatchSet ps1 = new PatchSet(new PatchSet.Id(ID, 1));
+    ps1.setUploader(new Account.Id(2000));
+    ps1.setRevision(new RevId("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"));
+    ps1.setCreatedOn(cols.createdOn());
+    ByteString ps1Bytes = toByteString(ps1, PATCH_SET_CODEC);
+    assertThat(ps1Bytes.size()).isEqualTo(66);
+
+    PatchSet ps2 = new PatchSet(new PatchSet.Id(ID, 2));
+    ps2.setUploader(new Account.Id(3000));
+    ps2.setRevision(new RevId("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"));
+    ps2.setCreatedOn(cols.lastUpdatedOn());
+    ByteString ps2Bytes = toByteString(ps2, PATCH_SET_CODEC);
+    assertThat(ps2Bytes.size()).isEqualTo(66);
+    assertThat(ps2Bytes).isNotEqualTo(ps1Bytes);
+
+    assertRoundTrip(
+        newBuilder()
+            .patchSets(ImmutableMap.of(ps2.getId(), ps2, ps1.getId(), ps1).entrySet())
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPatchSet(ps2Bytes)
+            .addPatchSet(ps1Bytes)
+            .build());
+  }
+
+  @Test
+  public void serializeApprovals() throws Exception {
+    PatchSetApproval a1 =
+        new PatchSetApproval(
+            new PatchSetApproval.Key(
+                new PatchSet.Id(ID, 1), new Account.Id(2001), new LabelId("Code-Review")),
+            (short) 1,
+            new Timestamp(1212L));
+    ByteString a1Bytes = toByteString(a1, APPROVAL_CODEC);
+    assertThat(a1Bytes.size()).isEqualTo(43);
+
+    PatchSetApproval a2 =
+        new PatchSetApproval(
+            new PatchSetApproval.Key(
+                new PatchSet.Id(ID, 1), new Account.Id(2002), new LabelId("Verified")),
+            (short) -1,
+            new Timestamp(3434L));
+    ByteString a2Bytes = toByteString(a2, APPROVAL_CODEC);
+    assertThat(a2Bytes.size()).isEqualTo(49);
+    assertThat(a2Bytes).isNotEqualTo(a1Bytes);
+
+    assertRoundTrip(
+        newBuilder()
+            .approvals(
+                ImmutableListMultimap.of(a2.getPatchSetId(), a2, a1.getPatchSetId(), a1).entries())
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addApproval(a2Bytes)
+            .addApproval(a1Bytes)
+            .build());
+  }
+
+  @Test
+  public void serializeReviewers() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .reviewers(
+                ReviewerSet.fromTable(
+                    ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>builder()
+                        .put(ReviewerStateInternal.CC, new Account.Id(2001), new Timestamp(1212L))
+                        .put(
+                            ReviewerStateInternal.REVIEWER,
+                            new Account.Id(2002),
+                            new Timestamp(3434L))
+                        .build()))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addReviewer(
+                ReviewerSetEntryProto.newBuilder()
+                    .setState("CC")
+                    .setAccountId(2001)
+                    .setTimestamp(1212L))
+            .addReviewer(
+                ReviewerSetEntryProto.newBuilder()
+                    .setState("REVIEWER")
+                    .setAccountId(2002)
+                    .setTimestamp(3434L))
+            .build());
+  }
+
+  @Test
+  public void serializeReviewersByEmail() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .reviewersByEmail(
+                ReviewerByEmailSet.fromTable(
+                    ImmutableTable.<ReviewerStateInternal, Address, Timestamp>builder()
+                        .put(
+                            ReviewerStateInternal.CC,
+                            new Address("Name1", "email1@example.com"),
+                            new Timestamp(1212L))
+                        .put(
+                            ReviewerStateInternal.REVIEWER,
+                            new Address("Name2", "email2@example.com"),
+                            new Timestamp(3434L))
+                        .build()))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addReviewerByEmail(
+                ReviewerByEmailSetEntryProto.newBuilder()
+                    .setState("CC")
+                    .setAddress("Name1 <email1@example.com>")
+                    .setTimestamp(1212L))
+            .addReviewerByEmail(
+                ReviewerByEmailSetEntryProto.newBuilder()
+                    .setState("REVIEWER")
+                    .setAddress("Name2 <email2@example.com>")
+                    .setTimestamp(3434L))
+            .build());
+  }
+
+  @Test
+  public void serializeReviewersByEmailWithNullName() throws Exception {
+    ChangeNotesState actual =
+        assertRoundTrip(
+            newBuilder()
+                .reviewersByEmail(
+                    ReviewerByEmailSet.fromTable(
+                        ImmutableTable.of(
+                            ReviewerStateInternal.CC,
+                            new Address("emailonly@example.com"),
+                            new Timestamp(1212L))))
+                .build(),
+            ChangeNotesStateProto.newBuilder()
+                .setMetaId(SHA_BYTES)
+                .setChangeId(ID.get())
+                .setColumns(colsProto)
+                .addReviewerByEmail(
+                    ReviewerByEmailSetEntryProto.newBuilder()
+                        .setState("CC")
+                        .setAddress("emailonly@example.com")
+                        .setTimestamp(1212L))
+                .build());
+
+    // Address doesn't consider the name field in equals, so we have to check it manually.
+    // TODO(dborowitz): Fix Address#equals.
+    ImmutableSet<Address> ccs = actual.reviewersByEmail().byState(ReviewerStateInternal.CC);
+    assertThat(ccs).hasSize(1);
+    Address address = Iterables.getOnlyElement(ccs);
+    assertThat(address.getName()).isNull();
+    assertThat(address.getEmail()).isEqualTo("emailonly@example.com");
+  }
+
+  @Test
+  public void serializePendingReviewers() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .pendingReviewers(
+                ReviewerSet.fromTable(
+                    ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>builder()
+                        .put(ReviewerStateInternal.CC, new Account.Id(2001), new Timestamp(1212L))
+                        .put(
+                            ReviewerStateInternal.REVIEWER,
+                            new Account.Id(2002),
+                            new Timestamp(3434L))
+                        .build()))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPendingReviewer(
+                ReviewerSetEntryProto.newBuilder()
+                    .setState("CC")
+                    .setAccountId(2001)
+                    .setTimestamp(1212L))
+            .addPendingReviewer(
+                ReviewerSetEntryProto.newBuilder()
+                    .setState("REVIEWER")
+                    .setAccountId(2002)
+                    .setTimestamp(3434L))
+            .build());
+  }
+
+  @Test
+  public void serializePendingReviewersByEmail() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .pendingReviewersByEmail(
+                ReviewerByEmailSet.fromTable(
+                    ImmutableTable.<ReviewerStateInternal, Address, Timestamp>builder()
+                        .put(
+                            ReviewerStateInternal.CC,
+                            new Address("Name1", "email1@example.com"),
+                            new Timestamp(1212L))
+                        .put(
+                            ReviewerStateInternal.REVIEWER,
+                            new Address("Name2", "email2@example.com"),
+                            new Timestamp(3434L))
+                        .build()))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPendingReviewerByEmail(
+                ReviewerByEmailSetEntryProto.newBuilder()
+                    .setState("CC")
+                    .setAddress("Name1 <email1@example.com>")
+                    .setTimestamp(1212L))
+            .addPendingReviewerByEmail(
+                ReviewerByEmailSetEntryProto.newBuilder()
+                    .setState("REVIEWER")
+                    .setAddress("Name2 <email2@example.com>")
+                    .setTimestamp(3434L))
+            .build());
+  }
+
+  @Test
+  public void serializeAllPastReviewers() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .allPastReviewers(ImmutableList.of(new Account.Id(2002), new Account.Id(2001)))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPastReviewer(2002)
+            .addPastReviewer(2001)
+            .build());
+  }
+
+  @Test
+  public void serializeReviewerUpdates() throws Exception {
+    assertRoundTrip(
+        newBuilder()
+            .reviewerUpdates(
+                ImmutableList.of(
+                    ReviewerStatusUpdate.create(
+                        new Timestamp(1212L),
+                        new Account.Id(1000),
+                        new Account.Id(2002),
+                        ReviewerStateInternal.CC),
+                    ReviewerStatusUpdate.create(
+                        new Timestamp(3434L),
+                        new Account.Id(1000),
+                        new Account.Id(2001),
+                        ReviewerStateInternal.REVIEWER)))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addReviewerUpdate(
+                ReviewerStatusUpdateProto.newBuilder()
+                    .setDate(1212L)
+                    .setUpdatedBy(1000)
+                    .setReviewer(2002)
+                    .setState("CC"))
+            .addReviewerUpdate(
+                ReviewerStatusUpdateProto.newBuilder()
+                    .setDate(3434L)
+                    .setUpdatedBy(1000)
+                    .setReviewer(2001)
+                    .setState("REVIEWER"))
+            .build());
+  }
+
+  @Test
+  public void serializeSubmitRecords() throws Exception {
+    SubmitRecord sr1 = new SubmitRecord();
+    sr1.status = SubmitRecord.Status.OK;
+
+    SubmitRecord sr2 = new SubmitRecord();
+    sr2.status = SubmitRecord.Status.FORCED;
+
+    assertRoundTrip(
+        newBuilder().submitRecords(ImmutableList.of(sr2, sr1)).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addSubmitRecord("{\"status\":\"FORCED\"}")
+            .addSubmitRecord("{\"status\":\"OK\"}")
+            .build());
+  }
+
+  @Test
+  public void serializeChangeMessages() throws Exception {
+    ChangeMessage m1 =
+        new ChangeMessage(
+            new ChangeMessage.Key(ID, "uuid1"),
+            new Account.Id(1000),
+            new Timestamp(1212L),
+            new PatchSet.Id(ID, 1));
+    ByteString m1Bytes = toByteString(m1, MESSAGE_CODEC);
+    assertThat(m1Bytes.size()).isEqualTo(35);
+
+    ChangeMessage m2 =
+        new ChangeMessage(
+            new ChangeMessage.Key(ID, "uuid2"),
+            new Account.Id(2000),
+            new Timestamp(3434L),
+            new PatchSet.Id(ID, 2));
+    ByteString m2Bytes = toByteString(m2, MESSAGE_CODEC);
+    assertThat(m2Bytes.size()).isEqualTo(35);
+    assertThat(m2Bytes).isNotEqualTo(m1Bytes);
+
+    assertRoundTrip(
+        newBuilder().changeMessages(ImmutableList.of(m2, m1)).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addChangeMessage(m2Bytes)
+            .addChangeMessage(m1Bytes)
+            .build());
+  }
+
+  @Test
+  public void serializePublishedComments() throws Exception {
+    Comment c1 =
+        new Comment(
+            new Comment.Key("uuid1", "file1", 1),
+            new Account.Id(1001),
+            new Timestamp(1212L),
+            (short) 1,
+            "message 1",
+            "serverId",
+            false);
+    c1.setRevId(new RevId("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"));
+    String c1Json = Serializer.GSON.toJson(c1);
+
+    Comment c2 =
+        new Comment(
+            new Comment.Key("uuid2", "file2", 2),
+            new Account.Id(1002),
+            new Timestamp(3434L),
+            (short) 2,
+            "message 2",
+            "serverId",
+            true);
+    c2.setRevId(new RevId("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"));
+    String c2Json = Serializer.GSON.toJson(c2);
+
+    assertRoundTrip(
+        newBuilder()
+            .publishedComments(
+                ImmutableListMultimap.of(new RevId(c2.revId), c2, new RevId(c1.revId), c1))
+            .build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .addPublishedComment(c2Json)
+            .addPublishedComment(c1Json)
+            .build());
+  }
+
+  @Test
+  public void serializeReadOnlyUntil() throws Exception {
+    assertRoundTrip(
+        newBuilder().readOnlyUntil(new Timestamp(1212L)).build(),
+        ChangeNotesStateProto.newBuilder()
+            .setMetaId(SHA_BYTES)
+            .setChangeId(ID.get())
+            .setColumns(colsProto)
+            .setReadOnlyUntil(1212L)
+            .setHasReadOnlyUntil(true)
+            .build());
+  }
+
+  @Test
+  public void changeNotesStateMethods() throws Exception {
+    assertThatSerializedClass(ChangeNotesState.class)
+        .hasAutoValueMethods(
+            ImmutableMap.<String, Type>builder()
+                .put("metaId", ObjectId.class)
+                .put("changeId", Change.Id.class)
+                .put("columns", ChangeColumns.class)
+                .put("pastAssignees", new TypeLiteral<ImmutableSet<Account.Id>>() {}.getType())
+                .put("hashtags", new TypeLiteral<ImmutableSet<String>>() {}.getType())
+                .put(
+                    "patchSets",
+                    new TypeLiteral<ImmutableList<Map.Entry<PatchSet.Id, PatchSet>>>() {}.getType())
+                .put(
+                    "approvals",
+                    new TypeLiteral<
+                        ImmutableList<Map.Entry<PatchSet.Id, PatchSetApproval>>>() {}.getType())
+                .put("reviewers", ReviewerSet.class)
+                .put("reviewersByEmail", ReviewerByEmailSet.class)
+                .put("pendingReviewers", ReviewerSet.class)
+                .put("pendingReviewersByEmail", ReviewerByEmailSet.class)
+                .put("allPastReviewers", new TypeLiteral<ImmutableList<Account.Id>>() {}.getType())
+                .put(
+                    "reviewerUpdates",
+                    new TypeLiteral<ImmutableList<ReviewerStatusUpdate>>() {}.getType())
+                .put("submitRecords", new TypeLiteral<ImmutableList<SubmitRecord>>() {}.getType())
+                .put("changeMessages", new TypeLiteral<ImmutableList<ChangeMessage>>() {}.getType())
+                .put(
+                    "publishedComments",
+                    new TypeLiteral<ImmutableListMultimap<RevId, Comment>>() {}.getType())
+                .put("readOnlyUntil", Timestamp.class)
+                .build());
+  }
+
+  @Test
+  public void changeColumnsMethods() throws Exception {
+    assertThatSerializedClass(ChangeColumns.class)
+        .hasAutoValueMethods(
+            ImmutableMap.<String, Type>builder()
+                .put("changeKey", Change.Key.class)
+                .put("createdOn", Timestamp.class)
+                .put("lastUpdatedOn", Timestamp.class)
+                .put("owner", Account.Id.class)
+                .put("branch", String.class)
+                .put("currentPatchSetId", PatchSet.Id.class)
+                .put("subject", String.class)
+                .put("topic", String.class)
+                .put("originalSubject", String.class)
+                .put("submissionId", String.class)
+                .put("assignee", Account.Id.class)
+                .put("status", Change.Status.class)
+                .put("isPrivate", boolean.class)
+                .put("workInProgress", boolean.class)
+                .put("reviewStarted", boolean.class)
+                .put("revertOf", Change.Id.class)
+                .put("toBuilder", ChangeNotesState.ChangeColumns.Builder.class)
+                .build());
+  }
+
+  @Test
+  public void patchSetFields() throws Exception {
+    assertThatSerializedClass(PatchSet.class)
+        .hasFields(
+            ImmutableMap.<String, Type>builder()
+                .put("id", PatchSet.Id.class)
+                .put("revision", RevId.class)
+                .put("uploader", Account.Id.class)
+                .put("createdOn", Timestamp.class)
+                .put("groups", String.class)
+                .put("pushCertificate", String.class)
+                .put("description", String.class)
+                .build());
+  }
+
+  @Test
+  public void patchSetApprovalFields() throws Exception {
+    assertThatSerializedClass(PatchSetApproval.Key.class)
+        .hasFields(
+            ImmutableMap.<String, Type>builder()
+                .put("patchSetId", PatchSet.Id.class)
+                .put("accountId", Account.Id.class)
+                .put("categoryId", LabelId.class)
+                .build());
+    assertThatSerializedClass(PatchSetApproval.class)
+        .hasFields(
+            ImmutableMap.<String, Type>builder()
+                .put("key", PatchSetApproval.Key.class)
+                .put("value", short.class)
+                .put("granted", Timestamp.class)
+                .put("tag", String.class)
+                .put("realAccountId", Account.Id.class)
+                .put("postSubmit", boolean.class)
+                .build());
+  }
+
+  @Test
+  public void reviewerSetFields() throws Exception {
+    assertThatSerializedClass(ReviewerSet.class)
+        .hasFields(
+            ImmutableMap.of(
+                "table",
+                    new TypeLiteral<
+                        ImmutableTable<
+                            ReviewerStateInternal, Account.Id, Timestamp>>() {}.getType(),
+                "accounts", new TypeLiteral<ImmutableSet<Account.Id>>() {}.getType()));
+  }
+
+  @Test
+  public void reviewerByEmailSetFields() throws Exception {
+    assertThatSerializedClass(ReviewerByEmailSet.class)
+        .hasFields(
+            ImmutableMap.of(
+                "table",
+                    new TypeLiteral<
+                        ImmutableTable<ReviewerStateInternal, Address, Timestamp>>() {}.getType(),
+                "users", new TypeLiteral<ImmutableSet<Address>>() {}.getType()));
+  }
+
+  @Test
+  public void reviewerStatusUpdateMethods() throws Exception {
+    assertThatSerializedClass(ReviewerStatusUpdate.class)
+        .hasAutoValueMethods(
+            ImmutableMap.of(
+                "date", Timestamp.class,
+                "updatedBy", Account.Id.class,
+                "reviewer", Account.Id.class,
+                "state", ReviewerStateInternal.class));
+  }
+
+  @Test
+  public void submitRecordFields() throws Exception {
+    assertThatSerializedClass(SubmitRecord.class)
+        .hasFields(
+            ImmutableMap.of(
+                "status",
+                SubmitRecord.Status.class,
+                "labels",
+                new TypeLiteral<List<SubmitRecord.Label>>() {}.getType(),
+                "requirements",
+                new TypeLiteral<List<SubmitRequirement>>() {}.getType(),
+                "errorMessage",
+                String.class));
+    assertThatSerializedClass(SubmitRecord.Label.class)
+        .hasFields(
+            ImmutableMap.of(
+                "label", String.class,
+                "status", SubmitRecord.Label.Status.class,
+                "appliedBy", Account.Id.class));
+    assertThatSerializedClass(SubmitRequirement.class)
+        .hasAutoValueMethods(
+            ImmutableMap.of(
+                "fallbackText", String.class,
+                "type", String.class,
+                "data", new TypeLiteral<ImmutableMap<String, String>>() {}.getType()));
+  }
+
+  @Test
+  public void changeMessageFields() throws Exception {
+    assertThatSerializedClass(ChangeMessage.Key.class)
+        .hasFields(ImmutableMap.of("changeId", Change.Id.class, "uuid", String.class));
+    assertThatSerializedClass(ChangeMessage.class)
+        .hasFields(
+            ImmutableMap.<String, Type>builder()
+                .put("key", ChangeMessage.Key.class)
+                .put("author", Account.Id.class)
+                .put("writtenOn", Timestamp.class)
+                .put("message", String.class)
+                .put("patchset", PatchSet.Id.class)
+                .put("tag", String.class)
+                .put("realAuthor", Account.Id.class)
+                .build());
+  }
+
+  @Test
+  public void commentFields() throws Exception {
+    assertThatSerializedClass(Comment.Key.class)
+        .hasFields(
+            ImmutableMap.of(
+                "uuid", String.class, "filename", String.class, "patchSetId", int.class));
+    assertThatSerializedClass(Comment.Identity.class).hasFields(ImmutableMap.of("id", int.class));
+    assertThatSerializedClass(Comment.Range.class)
+        .hasFields(
+            ImmutableMap.of(
+                "startLine", int.class,
+                "startChar", int.class,
+                "endLine", int.class,
+                "endChar", int.class));
+    assertThatSerializedClass(Comment.class)
+        .hasFields(
+            ImmutableMap.<String, Type>builder()
+                .put("key", Comment.Key.class)
+                .put("lineNbr", int.class)
+                .put("author", Comment.Identity.class)
+                .put("realAuthor", Comment.Identity.class)
+                .put("writtenOn", Timestamp.class)
+                .put("side", short.class)
+                .put("message", String.class)
+                .put("parentUuid", String.class)
+                .put("range", Comment.Range.class)
+                .put("tag", String.class)
+                .put("revId", String.class)
+                .put("serverId", String.class)
+                .put("unresolved", boolean.class)
+                .put("legacyFormat", boolean.class)
+                .build());
+  }
+
+  private static ChangeNotesStateProto toProto(ChangeNotesState state) throws Exception {
+    return ChangeNotesStateProto.parseFrom(Serializer.INSTANCE.serialize(state));
+  }
+
+  private static ChangeNotesState assertRoundTrip(
+      ChangeNotesState state, ChangeNotesStateProto expectedProto) throws Exception {
+    ChangeNotesStateProto actualProto = toProto(state);
+    assertThat(actualProto).isEqualTo(expectedProto);
+    ChangeNotesState actual = Serializer.INSTANCE.deserialize(Serializer.INSTANCE.serialize(state));
+    assertThat(actual).isEqualTo(state);
+    // It's possible that ChangeNotesState contains objects which implement equals without taking
+    // into account all fields. Return the actual deserialized instance so that callers can perform
+    // additional assertions if necessary.
+    return actual;
+  }
+
+  private static ByteString toByteString(ObjectId id) {
+    byte[] buf = new byte[Constants.OBJECT_ID_LENGTH];
+    id.copyRawTo(buf, 0);
+    return ByteString.copyFrom(buf);
+  }
+
+  private <T> ByteString toByteString(T object, ProtobufCodec<T> codec) {
+    return ProtoCacheSerializers.toByteString(object, codec);
+  }
+}
diff --git a/lib/truth/BUILD b/lib/truth/BUILD
index cb17269..82cd98a 100644
--- a/lib/truth/BUILD
+++ b/lib/truth/BUILD
@@ -19,3 +19,31 @@
         "//lib:guava",
     ],
 )
+
+java_library(
+    name = "truth-liteproto-extension",
+    data = ["//lib:LICENSE-DO_NOT_DISTRIBUTE"],
+    visibility = ["//visibility:private"],
+    exports = ["@truth-liteproto-extension//jar"],
+    runtime_deps = [
+        ":truth",
+        "//lib:guava",
+        "//lib:protobuf",
+    ],
+)
+
+java_library(
+    name = "truth-proto-extension",
+    data = ["//lib:LICENSE-DO_NOT_DISTRIBUTE"],
+    visibility = ["//visibility:public"],
+    exports = [
+        ":truth-liteproto-extension",
+        "@truth-proto-extension//jar",
+    ],
+    runtime_deps = [
+        ":truth",
+        ":truth-liteproto-extension",
+        "//lib:guava",
+        "//lib:protobuf",
+    ],
+)
diff --git a/proto/cache.proto b/proto/cache.proto
index 634b595..7e2e75a 100644
--- a/proto/cache.proto
+++ b/proto/cache.proto
@@ -45,3 +45,142 @@
   int64 expires_at = 4;
   string provider_id = 5;
 }
+
+
+// Serialized form of com.google.gerrit.server.notedb.ChangeNotesCache.Key.
+// Next ID: 4
+message ChangeNotesKeyProto {
+  string project = 1;
+  int32 change_id = 2;
+  bytes id = 3;
+}
+
+// Serialized from of com.google.gerrit.server.notedb.ChangeNotesState.
+//
+// Note on embedded protos: this is just for storing in a cache, so some formats
+// were chosen ease of coding the initial implementation. In particular, where
+// there already exists another serialization mechanism in Gerrit for
+// serializing a particular field, we use that rather than defining a new proto
+// type. This includes ReviewDb types that can be serialized to proto using
+// ProtobufCodec as well as NoteDb and indexed types that are serialized using
+// JSON. We can always revisit this decision later, particularly when we
+// eliminate the ReviewDb types; it just requires bumping the cache version.
+//
+// Note on nullability: there are a lot of nullable fields in ChangeNotesState
+// and its dependencies. It's likely we could make some of them non-nullable,
+// but each one of those would be a potentially significant amount of cleanup,
+// and there's no guarantee we'd be able to eliminate all of them. (For a less
+// complex class, it's likely the cleanup would be more feasible.)
+//
+// Instead, we just take the tedious yet simple approach of having a "has_foo"
+// field for each nullable field "foo", indicating whether or not foo is null.
+//
+// Next ID: 19
+message ChangeNotesStateProto {
+  // Effectively required, even though the corresponding ChangeNotesState field
+  // is optional, since the field is only absent when NoteDb is disabled, in
+  // which case attempting to use the ChangeNotesCache is programmer error.
+  bytes meta_id = 1;
+
+  int32 change_id = 2;
+
+  // Next ID: 24
+  message ChangeColumnsProto {
+    string change_key = 1;
+
+    int64 created_on = 2;
+
+    int64 last_updated_on = 3;
+
+    int32 owner = 4;
+
+    string branch = 5;
+
+    int32 current_patch_set_id = 6;
+    bool has_current_patch_set_id = 7;
+
+    string subject = 8;
+
+    string topic = 9;
+    bool has_topic = 10;
+
+    string original_subject = 11;
+    bool has_original_subject = 12;
+
+    string submission_id = 13;
+    bool has_submission_id = 14;
+
+    int32 assignee = 15;
+    bool has_assignee = 16;
+
+    string status = 17;
+    bool has_status = 18;
+
+    bool is_private = 19;
+
+    bool work_in_progress = 20;
+
+    bool review_started = 21;
+
+    int32 revert_of = 22;
+    bool has_revert_of = 23;
+  }
+  // Effectively required, even though the corresponding ChangeNotesState field
+  // is optional, since the field is only absent when NoteDb is disabled, in
+  // which case attempting to use the ChangeNotesCache is programmer error.
+  ChangeColumnsProto columns = 3;
+
+  repeated int32 past_assignee = 4;
+
+  repeated string hashtag = 5;
+
+  // Raw PatchSet proto as produced by ProtobufCodec.
+  repeated bytes patch_set = 6;
+
+  // Raw PatchSetApproval proto as produced by ProtobufCodec.
+  repeated bytes approval = 7;
+
+  // Next ID: 4
+  message ReviewerSetEntryProto {
+    string state = 1;
+    int32 account_id = 2;
+    int64 timestamp = 3;
+  }
+  repeated ReviewerSetEntryProto reviewer = 8;
+
+  // Next ID: 4
+  message ReviewerByEmailSetEntryProto {
+    string state = 1;
+    string address = 2;
+    int64 timestamp = 3;
+  }
+  repeated ReviewerByEmailSetEntryProto reviewer_by_email = 9;
+
+  repeated ReviewerSetEntryProto pending_reviewer = 10;
+
+  repeated ReviewerByEmailSetEntryProto pending_reviewer_by_email = 11;
+
+  repeated int32 past_reviewer = 12;
+
+  // Next ID: 5
+  message ReviewerStatusUpdateProto {
+    int64 date = 1;
+    int32 updated_by = 2;
+    int32 reviewer = 3;
+    string state = 4;
+  }
+  repeated ReviewerStatusUpdateProto reviewer_update = 13;
+
+  // JSON produced from
+  // com.google.gerrit.server.index.change.ChangeField.StoredSubmitRecord.
+  repeated string submit_record = 14;
+
+  // Raw ChangeMessage proto as produced by ProtobufCodec.
+  repeated bytes change_message = 15;
+
+  // JSON produced from com.google.gerrit.reviewdb.client.Comment.
+  repeated string published_comment = 16;
+
+  int64 read_only_until = 17;
+  bool has_read_only_until = 18;
+}