diff --git a/Documentation/dev-bazel.txt b/Documentation/dev-bazel.txt
index 61565f8..c3237ed 100644
--- a/Documentation/dev-bazel.txt
+++ b/Documentation/dev-bazel.txt
@@ -365,6 +365,13 @@
   bazel test --test_tag_filters=api,git //...
 ----
 
+To run the tests against a specific index backend (LUCENE, FAKE):
+----
+  bazel test --test_env=GERRIT_INDEX_TYPE=LUCENE //...
+----
+
+Elastic search is not currently supported in integration tests.
+
 The following values are currently supported for the group name:
 
 * annotation
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png b/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png
deleted file mode 100644
index 69a28ec..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-change-info.png b/Documentation/images/gwt-user-review-ui-change-screen-change-info.png
deleted file mode 100644
index e92b49d..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-change-info.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png b/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png
deleted file mode 100644
index 097637e..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png b/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png
deleted file mode 100644
index fe0c1d1..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png b/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png
deleted file mode 100644
index ad30fe2..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-not-current.png b/Documentation/images/gwt-user-review-ui-change-screen-not-current.png
deleted file mode 100644
index 9a87c67..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-not-current.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-permalink.png b/Documentation/images/gwt-user-review-ui-change-screen-permalink.png
deleted file mode 100644
index a1aede9..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-permalink.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png b/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png
deleted file mode 100644
index 120b99c..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png b/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png
deleted file mode 100644
index 2ecc47e..0000000
--- a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png b/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png
deleted file mode 100644
index 6f63f0e4..0000000
--- a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/user-review-ui-change-screen-plugin-extensions.png b/Documentation/images/user-review-ui-change-screen-plugin-extensions.png
new file mode 100644
index 0000000..5d6fee7
--- /dev/null
+++ b/Documentation/images/user-review-ui-change-screen-plugin-extensions.png
Binary files differ
diff --git a/Documentation/js_licenses.txt b/Documentation/js_licenses.txt
index 0d8da89..813ff44 100644
--- a/Documentation/js_licenses.txt
+++ b/Documentation/js_licenses.txt
@@ -1077,6 +1077,38 @@
 ----
 
 
+[[immer]]
+immer
+
+* immer
+
+[[immer_license]]
+----
+MIT License
+
+Copyright (c) 2017 Michel Weststrate
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+----
+
+
 [[isarray]]
 isarray
 
diff --git a/Documentation/licenses.txt b/Documentation/licenses.txt
index ed1a336..11f9ff3 100644
--- a/Documentation/licenses.txt
+++ b/Documentation/licenses.txt
@@ -4036,6 +4036,38 @@
 ----
 
 
+[[immer]]
+immer
+
+* immer
+
+[[immer_license]]
+----
+MIT License
+
+Copyright (c) 2017 Michel Weststrate
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+----
+
+
 [[isarray]]
 isarray
 
diff --git a/Documentation/user-review-ui.txt b/Documentation/user-review-ui.txt
index 367908e..6f5f7297 100644
--- a/Documentation/user-review-ui.txt
+++ b/Documentation/user-review-ui.txt
@@ -218,7 +218,7 @@
 ** [[plugin-actions]]Further actions may be available if plugins are installed.
 
 +
-image::images/user-review-ui-change-screen-change-info-actions.png[width=600, link="images/user-review-ui-change-screen-change-info-actions.png"]
+image::images/user-review-ui-change-screen-change-info-actions.png[width=400, link="images/user-review-ui-change-screen-change-info-actions.png"]
 
 - [[labels]]Labels & Votes:
 +
@@ -259,7 +259,7 @@
 set is currently viewed can be seen from the `Patch Sets` drop-down
 panel in the change header.
 
-image::images/user-review-ui-change-screen-patch-sets.png[width=487, link="images/user-review-ui-change-screen-patch-sets.png"]
+image::images/user-review-ui-change-screen-patch-sets.png[width=300, link="images/user-review-ui-change-screen-patch-sets.png"]
 
 
 [[download]]
@@ -458,7 +458,7 @@
 comments; a summary comment is only added if the reply popup panel is
 open when the quick approve button is clicked.
 
-image::images/user-review-ui-change-screen-quick-approve.png[width=800, link="images/gwt-user-review-ui-change-screen-quick-approve.png"]
+image::images/user-review-ui-change-screen-quick-approve.png[width=800, link="images/user-review-ui-change-screen-quick-approve.png"]
 
 [[history]]
 === History
@@ -485,11 +485,11 @@
 [[plugin-extensions]]
 === Plugin Extensions
 
-Gerrit plugins may extend the change screen; they can add buttons for
-additional actions to the change info block and display arbitrary UI
-controls below the change info block.
+Gerrit plugins may extend the change screen. Java plugins in the
+backend can add additional actions to the triple-dot menu block.
+Frontend plugins can change the UI controls in arbitrary ways.
 
-image::images/gwt-user-review-ui-change-screen-plugin-extensions.png[width=800, link="images/gwt-user-review-ui-change-screen-plugin-extensions.png"]
+image::images/user-review-ui-change-screen-plugin-extensions.png[width=300, link="images/user-review-ui-change-screen-plugin-extensions.png"]
 
 [[side-by-side]]
 == Side-by-Side Diff Screen
@@ -509,7 +509,7 @@
 diff preference allows to control whether the files should be
 automatically marked as reviewed when they are viewed.
 
-image::images/user-review-ui-side-by-side-diff-screen-reviewed.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-reviewed.png"]
+image::images/user-review-ui-side-by-side-diff-screen-reviewed.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-reviewed.png"]
 
 [[patch-set-selection]]
 In the header, on each side, the list of patch sets is shown. Clicking
@@ -616,7 +616,7 @@
 File level comments are added by clicking the 'File' header at the top
 of the file.
 
-image::images/user-review-ui-side-by-side-diff-screen-file-level-comment.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-file-level-comment.png"]
+image::images/user-review-ui-side-by-side-diff-screen-file-level-comment.png[width=400, link="images/user-review-ui-side-by-side-diff-screen-file-level-comment.png"]
 
 [[diff-preferences]]
 === Diff Preferences
@@ -626,7 +626,7 @@
 preferences. The diff preferences can be accessed by clicking on the
 settings icon in the screen header.
 
-image::images/user-review-ui-side-by-side-diff-screen-preferences.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-preferences.png"]
+image::images/user-review-ui-side-by-side-diff-screen-preferences.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-preferences.png"]
 
 The following diff preferences can be configured:
 
@@ -673,7 +673,7 @@
 If many lines are skipped there are additional links to expand the
 context by ten lines before and after the skipped block.
 +
-image::images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png"]
+image::images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png"]
 
 - [[syntax-highlighting]]`Syntax Highlighting`:
 +
@@ -703,7 +703,7 @@
 a popup that shows a list of available keyboard shortcuts.
 
 
-image::images/user-review-ui-change-screen-keyboard-shortcuts.png[width=800, link="images/gwt-user-review-ui-change-screen-keyboard-shortcuts.png"]
+image::images/user-review-ui-change-screen-keyboard-shortcuts.png[width=800, link="images/user-review-ui-change-screen-keyboard-shortcuts.png"]
 
 
 In addition, Vim-like commands can be used to link:#key-navigation[
diff --git a/Documentation/user-search.txt b/Documentation/user-search.txt
index a2dc31f..a9779b1 100644
--- a/Documentation/user-search.txt
+++ b/Documentation/user-search.txt
@@ -702,6 +702,18 @@
 to one of the fields in the
 link:rest-api-changes.html#submit-record[SubmitRecord] REST API entity.
 
+`label:Code-Review=MAX`::
++
+Matches changes with label voted with the highest possible score.
+
+`label:Code-Review=MIN`::
++
+Matches changes with label voted with the lowest possible score.
+
+`label:Code-Review=ANY`::
++
+Matches changes with label voted with any score.
+
 `label:Non-Author-Code-Review=need`::
 +
 Matches changes where the submit rules indicate that a label named
diff --git a/java/com/google/gerrit/acceptance/BUILD b/java/com/google/gerrit/acceptance/BUILD
index 5ee1a08..fa62cd9 100644
--- a/java/com/google/gerrit/acceptance/BUILD
+++ b/java/com/google/gerrit/acceptance/BUILD
@@ -75,6 +75,7 @@
     "//java/com/google/gerrit/extensions/restapi/testing:restapi-test-util",
     "//java/com/google/gerrit/gpg/testing:gpg-test-util",
     "//java/com/google/gerrit/git/testing",
+    "//java/com/google/gerrit/index/testing",
 ]
 
 PGM_DEPLOY_ENV = [
diff --git a/java/com/google/gerrit/acceptance/GerritServer.java b/java/com/google/gerrit/acceptance/GerritServer.java
index 93c1237..085fef5 100644
--- a/java/com/google/gerrit/acceptance/GerritServer.java
+++ b/java/com/google/gerrit/acceptance/GerritServer.java
@@ -45,6 +45,8 @@
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.annotations.Exports;
 import com.google.gerrit.extensions.config.FactoryModule;
+import com.google.gerrit.index.IndexType;
+import com.google.gerrit.index.testing.FakeIndexModule;
 import com.google.gerrit.lucene.LuceneIndexModule;
 import com.google.gerrit.pgm.Daemon;
 import com.google.gerrit.pgm.Init;
@@ -449,9 +451,29 @@
     cfg.setString("gitweb", null, "cgi", "");
     cfg.setString(
         "accountPatchReviewDb", null, "url", JdbcAccountPatchReviewStore.TEST_IN_MEMORY_URL);
+
+    String configuredIndexBackend = cfg.getString("index", null, "type");
+    IndexType indexType;
+    if (configuredIndexBackend != null) {
+      // Explicitly configured index backend from gerrit.config trumps any other ways to configure
+      // index backends so that Reindex tests can be explicit about the backend they want to test
+      // against.
+      indexType = new IndexType(configuredIndexBackend);
+    } else {
+      // Allow configuring the index backend based on sys/env variables so that integration tests
+      // can be run against different index backends.
+      indexType = IndexType.fromEnvironment().orElse(new IndexType("fake"));
+    }
+    if (indexType.isLucene()) {
+      daemon.setIndexModule(
+          LuceneIndexModule.singleVersionAllLatest(0, ReplicaUtil.isReplica(baseConfig)));
+    } else {
+      daemon.setIndexModule(FakeIndexModule.latestVersion(false));
+    }
+    // Elastic search is not supported in integration tests yet.
+
     daemon.setEnableHttpd(desc.httpd());
-    daemon.setLuceneModule(
-        LuceneIndexModule.singleVersionAllLatest(0, ReplicaUtil.isReplica(baseConfig)));
+    daemon.setInMemory(true);
     daemon.setDatabaseForTesting(
         ImmutableList.of(
             new InMemoryTestingDatabaseModule(cfg, site, inMemoryRepoManager),
@@ -476,6 +498,8 @@
       String[] additionalArgs)
       throws Exception {
     requireNonNull(site);
+    daemon.addAdditionalSysModuleForTesting(
+        new ReindexProjectsAtStartup.Module(), new ReindexGroupsAtStartup.Module());
     ExecutorService daemonService = Executors.newSingleThreadExecutor();
     String[] args =
         Stream.concat(
diff --git a/java/com/google/gerrit/httpd/init/WebAppInitializer.java b/java/com/google/gerrit/httpd/init/WebAppInitializer.java
index 079f306..91d032e 100644
--- a/java/com/google/gerrit/httpd/init/WebAppInitializer.java
+++ b/java/com/google/gerrit/httpd/init/WebAppInitializer.java
@@ -122,6 +122,8 @@
 import com.google.inject.spi.Message;
 import com.google.inject.util.Providers;
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
@@ -365,6 +367,19 @@
       return LuceneIndexModule.latestVersion(false);
     } else if (indexType.isElasticsearch()) {
       return ElasticIndexModule.latestVersion(false);
+    } else if (indexType.isFake()) {
+      // Use Reflection so that we can omit the fake index binary in production code. Test code does
+      // compile the component in.
+      try {
+        Class<?> clazz = Class.forName("com.google.gerrit.index.testing.FakeIndexModule");
+        Method m = clazz.getMethod("latestVersion", boolean.class);
+        return (Module) m.invoke(null, false);
+      } catch (NoSuchMethodException
+          | ClassNotFoundException
+          | IllegalAccessException
+          | InvocationTargetException e) {
+        throw new IllegalStateException("can't create index", e);
+      }
     } else {
       throw new IllegalStateException("unsupported index.type = " + indexType);
     }
diff --git a/java/com/google/gerrit/index/IndexType.java b/java/com/google/gerrit/index/IndexType.java
index cade439..0c3a76a 100644
--- a/java/com/google/gerrit/index/IndexType.java
+++ b/java/com/google/gerrit/index/IndexType.java
@@ -14,8 +14,12 @@
 
 package com.google.gerrit.index;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.common.Nullable;
+import java.util.Optional;
 
 /**
  * Index types supported by the secondary index.
@@ -28,12 +32,42 @@
  * allows to not break that case upon core implementation changes.
  */
 public class IndexType {
+  public static final String SYS_PROP = "gerrit.index.type";
+  private static final String ENV_VAR = "GERRIT_INDEX_TYPE";
+
   private static final String LUCENE = "lucene";
   private static final String ELASTICSEARCH = "elasticsearch";
   private static final String FAKE = "fake";
 
   private final String type;
 
+  /**
+   * Returns the index type in case it was set by an environment variable. This is useful to run
+   * tests against a certain index backend.
+   */
+  public static Optional<IndexType> fromEnvironment() {
+    String value = System.getenv(ENV_VAR);
+    if (Strings.isNullOrEmpty(value)) {
+      value = System.getProperty(SYS_PROP);
+    }
+    if (Strings.isNullOrEmpty(value)) {
+      return Optional.empty();
+    }
+    value = value.toUpperCase().replace("-", "_");
+    IndexType type = new IndexType(value);
+    if (!Strings.isNullOrEmpty(System.getenv(ENV_VAR))) {
+      checkArgument(
+          type != null, "Invalid value for env variable %s: %s", ENV_VAR, System.getenv(ENV_VAR));
+    } else {
+      checkArgument(
+          type != null,
+          "Invalid value for system property %s: %s",
+          SYS_PROP,
+          System.getProperty(SYS_PROP));
+    }
+    return Optional.of(type);
+  }
+
   public IndexType(@Nullable String type) {
     this.type = type == null ? getDefault() : type.toLowerCase();
   }
diff --git a/java/com/google/gerrit/index/testing/FakeIndexModuleOnInit.java b/java/com/google/gerrit/index/testing/FakeIndexModuleOnInit.java
new file mode 100644
index 0000000..75d8de2
--- /dev/null
+++ b/java/com/google/gerrit/index/testing/FakeIndexModuleOnInit.java
@@ -0,0 +1,37 @@
+// Copyright (C) 2021 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.index.testing;
+
+import com.google.gerrit.index.testing.AbstractFakeIndex.FakeAccountIndex;
+import com.google.gerrit.index.testing.AbstractFakeIndex.FakeGroupIndex;
+import com.google.gerrit.server.index.account.AccountIndex;
+import com.google.gerrit.server.index.group.GroupIndex;
+import com.google.inject.AbstractModule;
+import com.google.inject.assistedinject.FactoryModuleBuilder;
+
+public class FakeIndexModuleOnInit extends AbstractModule {
+  @Override
+  protected void configure() {
+    install(
+        new FactoryModuleBuilder()
+            .implement(AccountIndex.class, FakeAccountIndex.class)
+            .build(AccountIndex.Factory.class));
+
+    install(
+        new FactoryModuleBuilder()
+            .implement(GroupIndex.class, FakeGroupIndex.class)
+            .build(GroupIndex.Factory.class));
+  }
+}
diff --git a/java/com/google/gerrit/pgm/Daemon.java b/java/com/google/gerrit/pgm/Daemon.java
index 29c5788..2b4cfef 100644
--- a/java/com/google/gerrit/pgm/Daemon.java
+++ b/java/com/google/gerrit/pgm/Daemon.java
@@ -87,6 +87,7 @@
 import com.google.gerrit.server.git.SearchingChangeCacheImpl;
 import com.google.gerrit.server.git.WorkQueue;
 import com.google.gerrit.server.group.PeriodicGroupIndexer;
+import com.google.gerrit.server.index.AbstractIndexModule;
 import com.google.gerrit.server.index.IndexModule;
 import com.google.gerrit.server.index.OnlineUpgrader;
 import com.google.gerrit.server.index.VersionManager;
@@ -128,6 +129,8 @@
 import com.google.inject.Provider;
 import com.google.inject.Stage;
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -207,7 +210,7 @@
   private Injector httpdInjector;
   private Path runFile;
   private boolean inMemoryTest;
-  private AbstractModule luceneModule;
+  private AbstractModule indexModule;
   private Module emailModule;
   private List<Module> testSysModules = new ArrayList<>();
   private List<Module> testSshModules = new ArrayList<>();
@@ -336,9 +339,13 @@
   }
 
   @VisibleForTesting
-  public void setLuceneModule(LuceneIndexModule m) {
-    luceneModule = m;
-    inMemoryTest = true;
+  public void setIndexModule(AbstractIndexModule m) {
+    indexModule = m;
+  }
+
+  @VisibleForTesting
+  public void setInMemory(boolean inMemory) {
+    this.inMemoryTest = inMemory;
   }
 
   @VisibleForTesting
@@ -523,8 +530,8 @@
   }
 
   private Module createIndexModule() {
-    if (luceneModule != null) {
-      return luceneModule;
+    if (indexModule != null) {
+      return indexModule;
     }
     if (indexType.isLucene()) {
       return LuceneIndexModule.latestVersion(replica);
@@ -532,6 +539,20 @@
     if (indexType.isElasticsearch()) {
       return ElasticIndexModule.latestVersion(replica);
     }
+    if (indexType.isFake()) {
+      // Use Reflection so that we can omit the fake index binary in production code. Test code does
+      // compile the component in.
+      try {
+        Class<?> clazz = Class.forName("com.google.gerrit.index.testing.FakeIndexModule");
+        Method m = clazz.getMethod("latestVersion", boolean.class);
+        return (Module) m.invoke(null, replica);
+      } catch (NoSuchMethodException
+          | ClassNotFoundException
+          | IllegalAccessException
+          | InvocationTargetException e) {
+        throw new IllegalStateException("can't create index", e);
+      }
+    }
     throw new IllegalStateException("unsupported index.type = " + indexType);
   }
 
diff --git a/java/com/google/gerrit/pgm/Reindex.java b/java/com/google/gerrit/pgm/Reindex.java
index 3935268..6e99007 100644
--- a/java/com/google/gerrit/pgm/Reindex.java
+++ b/java/com/google/gerrit/pgm/Reindex.java
@@ -39,6 +39,8 @@
 import com.google.inject.Injector;
 import com.google.inject.Key;
 import com.google.inject.Module;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
@@ -154,6 +156,21 @@
     } else if (indexType.isElasticsearch()) {
       indexModule =
           ElasticIndexModule.singleVersionWithExplicitVersions(versions, threads, replica);
+    } else if (indexType.isFake()) {
+      // Use Reflection so that we can omit the fake index binary in production code. Test code does
+      // compile the component in.
+      try {
+        Class<?> clazz = Class.forName("com.google.gerrit.index.testing.FakeIndexModule");
+        Method m =
+            clazz.getMethod(
+                "singleVersionWithExplicitVersions", Map.class, int.class, boolean.class);
+        indexModule = (Module) m.invoke(null, versions, threads, replica);
+      } catch (NoSuchMethodException
+          | ClassNotFoundException
+          | IllegalAccessException
+          | InvocationTargetException e) {
+        throw new IllegalStateException("can't create index", e);
+      }
     } else {
       throw new IllegalStateException("unsupported index.type = " + indexType);
     }
diff --git a/java/com/google/gerrit/pgm/init/BaseInit.java b/java/com/google/gerrit/pgm/init/BaseInit.java
index 62ff66a..c4b0040 100644
--- a/java/com/google/gerrit/pgm/init/BaseInit.java
+++ b/java/com/google/gerrit/pgm/init/BaseInit.java
@@ -32,6 +32,7 @@
 import com.google.gerrit.pgm.init.api.InstallPlugins;
 import com.google.gerrit.pgm.init.api.LibraryDownload;
 import com.google.gerrit.pgm.init.index.IndexManagerOnInit;
+import com.google.gerrit.pgm.init.index.IndexModuleOnInit;
 import com.google.gerrit.pgm.init.index.elasticsearch.ElasticIndexModuleOnInit;
 import com.google.gerrit.pgm.init.index.lucene.LuceneIndexModuleOnInit;
 import com.google.gerrit.pgm.util.SiteProgram;
@@ -57,6 +58,7 @@
 import com.google.inject.util.Providers;
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
 import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -418,6 +420,19 @@
         modules.add(new LuceneIndexModuleOnInit());
       } else if (indexType.isElasticsearch()) {
         modules.add(new ElasticIndexModuleOnInit());
+      } else if (indexType.isFake()) {
+        try {
+          Class<?> clazz = Class.forName("com.google.gerrit.index.testing.FakeIndexModuleOnInit");
+          Module indexOnInitModule = (Module) clazz.getDeclaredConstructor().newInstance();
+          modules.add(indexOnInitModule);
+        } catch (InstantiationException
+            | IllegalAccessException
+            | ClassNotFoundException
+            | NoSuchMethodException
+            | InvocationTargetException e) {
+          throw new IllegalStateException("unable to create fake index", e);
+        }
+        modules.add(new IndexModuleOnInit());
       } else {
         throw new IllegalStateException("unsupported index.type = " + indexType);
       }
diff --git a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
index 005aebb..454df66 100644
--- a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
+++ b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
@@ -659,7 +659,9 @@
   // Process as many commands as possible, but may leave some commands in state NOT_ATTEMPTED.
   private void processCommandsUnsafe(
       Collection<ReceiveCommand> commands, MultiProgressMonitor progress) {
-    logger.atFine().log("Calling user: %s", user.getLoggableName());
+    logger.atFine().log("Calling user: %s, commands: %d", user.getLoggableName(), commands.size());
+
+    // If the list of groups is large, the log entry may get dropped, so separate out.
     logger.atFine().log("Groups: %s", lazy(() -> user.getEffectiveGroups().getKnownGroups()));
 
     if (!projectState.getProject().getState().permitsWrite()) {
@@ -669,8 +671,6 @@
       return;
     }
 
-    logger.atFine().log("Parsing %d commands", commands.size());
-
     List<ReceiveCommand> magicCommands = new ArrayList<>();
     List<ReceiveCommand> regularCommands = new ArrayList<>();
 
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index 9c39c6e..810cd4d 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -43,11 +43,13 @@
 import com.google.common.flogger.FluentLogger;
 import com.google.common.io.Files;
 import com.google.common.primitives.Longs;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Address;
 import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.ChangeMessage;
+import com.google.gerrit.entities.LabelType;
 import com.google.gerrit.entities.LegacySubmitRequirement;
 import com.google.gerrit.entities.PatchSetApproval;
 import com.google.gerrit.entities.Project;
@@ -72,6 +74,7 @@
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.query.change.ChangeQueryBuilder;
 import com.google.gerrit.server.query.change.ChangeStatusPredicate;
+import com.google.gerrit.server.query.change.MagicLabelValue;
 import com.google.gson.Gson;
 import com.google.protobuf.MessageLite;
 import java.sql.Timestamp;
@@ -602,16 +605,35 @@
     for (PatchSetApproval a : cd.currentApprovals()) {
       if (a.value() != 0 && !a.isLegacySubmit()) {
         allApprovals.add(formatLabel(a.label(), a.value(), a.accountId()));
+        LabelType labelType = cd.getLabelTypes().byLabel(a.labelId());
+        allApprovals.addAll(getMaxMinAnyLabels(a.label(), a.value(), labelType, a.accountId()));
         if (owners && cd.change().getOwner().equals(a.accountId())) {
           allApprovals.add(formatLabel(a.label(), a.value(), ChangeQueryBuilder.OWNER_ACCOUNT_ID));
+          allApprovals.addAll(
+              getMaxMinAnyLabels(
+                  a.label(), a.value(), labelType, ChangeQueryBuilder.OWNER_ACCOUNT_ID));
         }
         distinctApprovals.add(formatLabel(a.label(), a.value()));
+        distinctApprovals.addAll(getMaxMinAnyLabels(a.label(), a.value(), labelType, null));
       }
     }
     allApprovals.addAll(distinctApprovals);
     return allApprovals;
   }
 
+  private static List<String> getMaxMinAnyLabels(
+      String label, short labelVal, LabelType labelType, @Nullable Account.Id accountId) {
+    List<String> labels = new ArrayList<>();
+    if (labelVal == labelType.getMaxPositive()) {
+      labels.add(formatLabel(label, MagicLabelValue.MAX.name(), accountId));
+    }
+    if (labelVal == labelType.getMaxNegative()) {
+      labels.add(formatLabel(label, MagicLabelValue.MIN.name(), accountId));
+    }
+    labels.add(formatLabel(label, MagicLabelValue.ANY.name(), accountId));
+    return labels;
+  }
+
   public static Set<String> getAuthorParts(ChangeData cd) {
     return SchemaUtil.getPersonParts(cd.getAuthor());
   }
@@ -696,6 +718,17 @@
         + (accountId != null ? "," + formatAccount(accountId) : "");
   }
 
+  public static String formatLabel(String label, String value) {
+    return formatLabel(label, value, null);
+  }
+
+  public static String formatLabel(String label, String value, @Nullable Account.Id accountId) {
+    return label.toLowerCase()
+        + "="
+        + value
+        + (accountId != null ? "," + formatAccount(accountId) : "");
+  }
+
   private static String formatAccount(Account.Id accountId) {
     if (ChangeQueryBuilder.OWNER_ACCOUNT_ID.equals(accountId)) {
       return ChangeQueryBuilder.ARG_ID_OWNER;
diff --git a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
index 6355674..879da4f 100644
--- a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
+++ b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
@@ -150,6 +150,9 @@
    */
   static final Schema<ChangeData> V63 = schema(V62, false);
 
+  /** Added support for MIN/MAX/ANY for {@link ChangeField#LABEL} */
+  static final Schema<ChangeData> V64 = schema(V63, false);
+
   /**
    * Name of the change index to be used when contacting index backends or loading configurations.
    */
diff --git a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
index 94b5442..131de74 100644
--- a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
+++ b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
@@ -973,7 +973,7 @@
     int eq = name.indexOf('=');
     if (args.getSchema().hasField(ChangeField.SUBMIT_RECORD) && eq > 0) {
       String statusName = name.substring(eq + 1).toUpperCase();
-      if (!isInt(statusName)) {
+      if (!isInt(statusName) && !MagicLabelValue.tryParse(statusName).isPresent()) {
         SubmitRecord.Label.Status status =
             Enums.getIfPresent(SubmitRecord.Label.Status.class, statusName).orNull();
         if (status == null) {
diff --git a/java/com/google/gerrit/server/query/change/LabelPredicate.java b/java/com/google/gerrit/server/query/change/LabelPredicate.java
index 38d1dbe..989b4bb 100644
--- a/java/com/google/gerrit/server/query/change/LabelPredicate.java
+++ b/java/com/google/gerrit/server/query/change/LabelPredicate.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.query.change;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.AccountGroup;
@@ -59,12 +60,12 @@
   protected static class Parsed {
     protected final String label;
     protected final String test;
-    protected final int expVal;
+    protected final int numericValue;
 
-    protected Parsed(String label, String test, int expVal) {
+    protected Parsed(String label, String test, int numericValue) {
       this.label = label;
       this.test = test;
-      this.expVal = expVal;
+      this.numericValue = numericValue;
     }
   }
 
@@ -83,6 +84,14 @@
 
   protected static List<Predicate<ChangeData>> predicates(Args args) {
     String v = args.value;
+
+    try {
+      MagicLabelVote mlv = MagicLabelVote.parseWithEquals(v);
+      return ImmutableList.of(new MagicLabelPredicate(args, mlv));
+    } catch (IllegalArgumentException e) {
+      // Try next format.
+    }
+
     Parsed parsed = null;
 
     try {
@@ -108,7 +117,7 @@
     } else {
       range =
           RangeUtil.getRange(
-              parsed.label, parsed.test, parsed.expVal, -MAX_LABEL_VALUE, MAX_LABEL_VALUE);
+              parsed.label, parsed.test, parsed.numericValue, -MAX_LABEL_VALUE, MAX_LABEL_VALUE);
     }
     String prefix = range.prefix;
     int min = range.min;
diff --git a/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java b/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java
new file mode 100644
index 0000000..e3c58e47
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java
@@ -0,0 +1,101 @@
+// Copyright (C) 2021 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.query.change;
+
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.LabelType;
+import com.google.gerrit.entities.LabelTypes;
+import com.google.gerrit.entities.LabelValue;
+import com.google.gerrit.index.query.Predicate;
+import com.google.gerrit.server.index.change.ChangeField;
+import com.google.gerrit.server.project.ProjectState;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public class MagicLabelPredicate extends ChangeIndexPredicate {
+  protected final LabelPredicate.Args args;
+  private final MagicLabelVote magicLabelVote;
+
+  public MagicLabelPredicate(LabelPredicate.Args args, MagicLabelVote magicLabelVote) {
+    super(ChangeField.LABEL, magicLabelVote.formatLabel());
+    this.args = args;
+    this.magicLabelVote = magicLabelVote;
+  }
+
+  @Override
+  public boolean match(ChangeData changeData) {
+    Change change = changeData.change();
+    if (change == null) {
+      // The change has disappeared.
+      //
+      return false;
+    }
+
+    Optional<ProjectState> project = args.projectCache.get(change.getDest().project());
+    if (!project.isPresent()) {
+      // The project has disappeared.
+      //
+      return false;
+    }
+
+    LabelType labelType = type(project.get().getLabelTypes(), magicLabelVote.label());
+    if (labelType == null) {
+      return false; // Label is not defined by this project.
+    }
+
+    switch (magicLabelVote.value()) {
+      case ANY:
+        return matchAny(changeData, labelType);
+      case MIN:
+        return matchNumeric(changeData, magicLabelVote.label(), labelType.getMin().getValue());
+      case MAX:
+        return matchNumeric(changeData, magicLabelVote.label(), labelType.getMax().getValue());
+    }
+
+    throw new IllegalStateException("Unsupported magic label value: " + magicLabelVote.value());
+  }
+
+  private boolean matchAny(ChangeData changeData, LabelType labelType) {
+    List<Predicate<ChangeData>> predicates = new ArrayList<>();
+    for (LabelValue labelValue : labelType.getValues()) {
+      if (labelValue.getValue() != 0) {
+        predicates.add(numericPredicate(labelType.getName(), labelValue.getValue()));
+      }
+    }
+    return or(predicates).asMatchable().match(changeData);
+  }
+
+  private boolean matchNumeric(ChangeData changeData, String label, short value) {
+    return numericPredicate(label, value).match(changeData);
+  }
+
+  private EqualsLabelPredicate numericPredicate(String label, short value) {
+    return new EqualsLabelPredicate(args, label, value, /* account= */ null);
+  }
+
+  protected static LabelType type(LabelTypes types, String toFind) {
+    if (types.byLabel(toFind) != null) {
+      return types.byLabel(toFind);
+    }
+
+    for (LabelType lt : types.getLabelTypes()) {
+      if (toFind.equalsIgnoreCase(lt.getName())) {
+        return lt;
+      }
+    }
+    return null;
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/MagicLabelValue.java b/java/com/google/gerrit/server/query/change/MagicLabelValue.java
new file mode 100644
index 0000000..c4bcbe3
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/MagicLabelValue.java
@@ -0,0 +1,31 @@
+// Copyright (C) 2021 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.query.change;
+
+import java.util.Optional;
+
+public enum MagicLabelValue {
+  ANY,
+  MIN,
+  MAX;
+
+  public static Optional<MagicLabelValue> tryParse(String value) {
+    try {
+      return Optional.of(MagicLabelValue.valueOf(value));
+    } catch (IllegalArgumentException e) {
+      return Optional.empty();
+    }
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/MagicLabelVote.java b/java/com/google/gerrit/server/query/change/MagicLabelVote.java
new file mode 100644
index 0000000..c29ac72
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/MagicLabelVote.java
@@ -0,0 +1,47 @@
+// Copyright (C) 2021 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.query.change;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Strings;
+import com.google.gerrit.entities.LabelType;
+import java.util.Locale;
+
+/** An entity representing a special label vote that's not numeric, e.g. MAX, MIN, etc... */
+@AutoValue
+public abstract class MagicLabelVote {
+  public static MagicLabelVote parseWithEquals(String text) {
+    checkArgument(!Strings.isNullOrEmpty(text), "Empty label vote");
+    int e = text.lastIndexOf('=');
+    checkArgument(e >= 0, "Label vote missing '=': %s", text);
+    String label = text.substring(0, e);
+    String voteValue = text.substring(e + 1);
+    return create(label, MagicLabelValue.valueOf(voteValue));
+  }
+
+  public static MagicLabelVote create(String label, MagicLabelValue value) {
+    return new AutoValue_MagicLabelVote(LabelType.checkNameInternal(label), value);
+  }
+
+  public abstract String label();
+
+  public abstract MagicLabelValue value();
+
+  public String formatLabel() {
+    return label().toLowerCase(Locale.US) + "=" + value().name();
+  }
+}
diff --git a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
index 0356cdd..53d0f18 100644
--- a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
+++ b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
@@ -19,7 +19,9 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import com.google.common.collect.Sets.SetView;
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.HumanComment;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.extensions.api.changes.AttentionSetInput;
@@ -60,6 +62,7 @@
  * This class is used to update the attention set when performing a review or replying on a change.
  */
 public class ReplyAttentionSetUpdates {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   private final PermissionBackend permissionBackend;
   private final AddToAttentionSetOp.Factory addToAttentionSetOpFactory;
@@ -316,11 +319,15 @@
     AttentionSetUtil.validateInput(add);
     try {
       Account.Id attentionUserId =
-          getAccountIdAndValidateUser(changeNotes, add.user, accountsChangedInCommit);
+          getAccountIdAndValidateUser(
+              changeNotes, add.user, accountsChangedInCommit, AttentionSetUpdate.Operation.ADD);
       addToAttentionSet(bu, changeNotes, attentionUserId, add.reason, false);
     } catch (AccountResolver.UnresolvableAccountException ex) {
       // This happens only when the account doesn't exist. Silently ignore it. If we threw an error
       // message here, then it would be possible to probe whether an account exists.
+    } catch (AuthException ex) {
+      // adding users without permission to the attention set should fail silently.
+      logger.atFine().log(ex.getMessage());
     }
   }
 
@@ -334,17 +341,25 @@
     AttentionSetUtil.validateInput(remove);
     try {
       Account.Id attentionUserId =
-          getAccountIdAndValidateUser(changeNotes, remove.user, accountsChangedInCommit);
+          getAccountIdAndValidateUser(
+              changeNotes,
+              remove.user,
+              accountsChangedInCommit,
+              AttentionSetUpdate.Operation.REMOVE);
       removeFromAttentionSet(bu, changeNotes, attentionUserId, remove.reason, false);
     } catch (AccountResolver.UnresolvableAccountException ex) {
       // This happens only when the account doesn't exist. Silently ignore it. If we threw an error
       // message here, then it would be possible to probe whether an account exists.
+    } catch (AuthException ex) {
+      // this should never happen since removing users with permissions should work.
+      logger.atSevere().log(ex.getMessage());
     }
   }
 
-  private Account.Id getAccountId(ChangeNotes changeNotes, String user)
+  private Account.Id getAccountId(
+      ChangeNotes changeNotes, String user, AttentionSetUpdate.Operation operation)
       throws ConfigInvalidException, IOException, UnprocessableEntityException,
-          PermissionBackendException {
+          PermissionBackendException, AuthException {
     Account.Id attentionUserId = accountResolver.resolve(user).asUnique().account().id();
     try {
       permissionBackend
@@ -352,22 +367,29 @@
           .change(changeNotes)
           .check(ChangePermission.READ);
     } catch (AuthException e) {
+      // If the change is private, it is okay to add the user to the attention set since that
+      // person will be granted visibility when a reviewer.
       if (!changeNotes.getChange().isPrivate()) {
-        // If the change is private, it is okay to add the user to the attention set since that
-        // person will be granted visibility when a reviewer.
-        throw new UnprocessableEntityException(
-            "Can't add to attention set: Read not permitted for " + attentionUserId, e);
+
+        // Removing users without access is allowed, adding is not allowed
+        if (operation == AttentionSetUpdate.Operation.ADD) {
+          throw new AuthException(
+              "Can't modify attention set: Read not permitted for " + attentionUserId, e);
+        }
       }
     }
     return attentionUserId;
   }
 
   private Account.Id getAccountIdAndValidateUser(
-      ChangeNotes changeNotes, String user, Set<Account.Id> accountsChangedInCommit)
+      ChangeNotes changeNotes,
+      String user,
+      Set<Account.Id> accountsChangedInCommit,
+      AttentionSetUpdate.Operation operation)
       throws ConfigInvalidException, IOException, PermissionBackendException,
-          UnprocessableEntityException, BadRequestException {
+          UnprocessableEntityException, BadRequestException, AuthException {
     try {
-      Account.Id attentionUserId = getAccountId(changeNotes, user);
+      Account.Id attentionUserId = getAccountId(changeNotes, user, operation);
       if (accountsChangedInCommit.contains(attentionUserId)) {
         throw new BadRequestException(
             String.format(
diff --git a/java/com/google/gerrit/truth/NullAwareCorrespondence.java b/java/com/google/gerrit/truth/NullAwareCorrespondence.java
index 687ad94..5b107a6 100644
--- a/java/com/google/gerrit/truth/NullAwareCorrespondence.java
+++ b/java/com/google/gerrit/truth/NullAwareCorrespondence.java
@@ -7,15 +7,6 @@
 // http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
-// Copyright (C) 2020 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
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index 42354ca..976e828 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -4020,6 +4020,86 @@
   }
 
   @Test
+  public void submitRequirement_withLabelEqualsMax() throws Exception {
+    configSubmitRequirement(
+        project,
+        SubmitRequirement.builder()
+            .setName("code-review")
+            .setSubmittabilityExpression(
+                SubmitRequirementExpression.create("label:code-review=MAX"))
+            .setAllowOverrideInChildProjects(false)
+            .build());
+
+    PushOneCommit.Result r = createChange();
+    String changeId = r.getChangeId();
+
+    ChangeInfo change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.UNSATISFIED);
+
+    voteLabel(changeId, "code-review", 2);
+    change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.SATISFIED);
+  }
+
+  @Test
+  public void submitRequirement_withLabelEqualsMinBlockingSubmission() throws Exception {
+    configSubmitRequirement(
+        project,
+        SubmitRequirement.builder()
+            .setName("code-review")
+            .setSubmittabilityExpression(
+                SubmitRequirementExpression.create("-label:code-review=MIN"))
+            .setAllowOverrideInChildProjects(false)
+            .build());
+
+    PushOneCommit.Result r = createChange();
+    String changeId = r.getChangeId();
+
+    ChangeInfo change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    // Requirement is satisfied because there are no votes
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.SATISFIED);
+
+    voteLabel(changeId, "code-review", -1);
+    change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    // Requirement is still satisfied because -1 is not the max negative value
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.SATISFIED);
+
+    voteLabel(changeId, "code-review", -2);
+    change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    // Requirement is now unsatisfied because -2 is the max negative value
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.UNSATISFIED);
+  }
+
+  @Test
+  public void submitRequirement_withLabelEqualsAny() throws Exception {
+    configSubmitRequirement(
+        project,
+        SubmitRequirement.builder()
+            .setName("code-review")
+            .setSubmittabilityExpression(
+                SubmitRequirementExpression.create("label:code-review=ANY"))
+            .setAllowOverrideInChildProjects(false)
+            .build());
+
+    PushOneCommit.Result r = createChange();
+    String changeId = r.getChangeId();
+
+    ChangeInfo change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.UNSATISFIED);
+
+    voteLabel(changeId, "code-review", 1);
+    change = gApi.changes().id(changeId).get();
+    assertThat(change.submitRequirements).hasSize(1);
+    assertSubmitRequirementStatus(change.submitRequirements, "code-review", Status.SATISFIED);
+  }
+
+  @Test
   public void submitRequirementIsSatisfied_whenSubmittabilityExpressionIsFulfilled()
       throws Exception {
     configSubmitRequirement(
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
index eb5bcba..4590d34 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
@@ -1207,10 +1207,15 @@
     ChangeApi originalChange = gApi.changes().id(project.get() + "~master~" + result.getChangeId());
 
     ChangeApi cherryPick = originalChange.revision(result.getCommit().name()).cherryPick(input);
+    String firstCherryPickChangeId = cherryPick.id();
     cherryPick.setWorkInProgress();
-    cherryPick = originalChange.revision(result.getCommit().name()).cherryPick(input);
+    gApi.changes()
+        .id(project.get() + "~master~" + result.getChangeId())
+        .revision(result.getCommit().name())
+        .cherryPick(input);
 
-    ChangeInfo secondCherryPickResult = cherryPick.get(ALL_REVISIONS);
+    ChangeInfo secondCherryPickResult =
+        gApi.changes().id(firstCherryPickChangeId).get(ALL_REVISIONS);
     assertThat(secondCherryPickResult.revisions).hasSize(2);
     assertThat(secondCherryPickResult.workInProgress).isNull();
   }
diff --git a/javatests/com/google/gerrit/acceptance/git/RefAdvertisementIT.java b/javatests/com/google/gerrit/acceptance/git/RefAdvertisementIT.java
index b7acbe2..16ccc35 100644
--- a/javatests/com/google/gerrit/acceptance/git/RefAdvertisementIT.java
+++ b/javatests/com/google/gerrit/acceptance/git/RefAdvertisementIT.java
@@ -38,7 +38,6 @@
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.entities.AccessSection;
 import com.google.gerrit.entities.AccountGroup;
-import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Permission;
@@ -69,7 +68,6 @@
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
-import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.lib.Repository;
@@ -1106,37 +1104,10 @@
 
   @Test
   public void receivePackOmitsMissingObject() throws Exception {
-    String rev = "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef";
     try (Repository repo = repoManager.openRepository(project);
         TestRepository<Repository> tr = new TestRepository<>(repo)) {
-      String subject = "Subject for missing commit";
-      Change c = new Change(cd3.change());
-      PatchSet.Id psId = PatchSet.id(cd3.getId(), 2);
-      c.setCurrentPatchSet(psId, subject, c.getOriginalSubject());
-
-      PersonIdent committer = serverIdent.get();
-      PersonIdent author =
-          noteUtil.newAccountIdIdent(getAccount(admin.id()).id(), committer.getWhen(), committer);
-      tr.branch(RefNames.changeMetaRef(cd3.getId()))
-          .commit()
-          .author(author)
-          .committer(committer)
-          .message(
-              "Update patch set "
-                  + psId.get()
-                  + "\n"
-                  + "\n"
-                  + "Patch-set: "
-                  + psId.get()
-                  + "\n"
-                  + "Commit: "
-                  + rev
-                  + "\n"
-                  + "Subject: "
-                  + subject
-                  + "\n")
-          .create();
-      indexer.index(c.getProject(), c.getId());
+      PatchSet.Id psId = PatchSet.id(cd3.getId(), 1);
+      tr.delete(psId.toRefName());
     }
 
     assertThat(getReceivePackRefs().additionalHaves()).containsExactly(obj(cd4, 1));
diff --git a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
index cad0b83..cac376f 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
@@ -31,14 +31,18 @@
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.api.GerritApi;
 import com.google.gerrit.extensions.common.ChangeInput;
+import com.google.gerrit.index.IndexDefinition;
 import com.google.gerrit.launcher.GerritLauncher;
 import com.google.gerrit.server.index.GerritIndexStatus;
 import com.google.gerrit.server.index.change.ChangeIndexCollection;
 import com.google.gerrit.server.index.change.ChangeSchemaDefinitions;
 import com.google.gerrit.server.query.change.InternalChangeQuery;
 import com.google.inject.Injector;
+import com.google.inject.Key;
 import com.google.inject.Provider;
+import com.google.inject.TypeLiteral;
 import java.nio.file.Files;
+import java.util.Collection;
 import java.util.Set;
 import java.util.function.Consumer;
 import org.eclipse.jgit.lib.Config;
@@ -48,9 +52,6 @@
 
 @NoHttpd
 public abstract class AbstractReindexTests extends StandaloneSiteTest {
-  /** @param injector injector */
-  public abstract void configureIndex(Injector injector) throws Exception;
-
   private static final String CHANGES = ChangeSchemaDefinitions.NAME;
 
   private Project.NameKey project;
@@ -223,10 +224,18 @@
     }
   }
 
+  protected static void createAllIndexes(Injector injector) {
+    Collection<IndexDefinition<?, ?, ?>> indexDefs =
+        injector.getInstance(Key.get(new TypeLiteral<Collection<IndexDefinition<?, ?, ?>>>() {}));
+    for (IndexDefinition<?, ?, ?> indexDef : indexDefs) {
+      indexDef.getIndexCollection().getSearchIndex().deleteAll();
+    }
+  }
+
   private void setUpChange() throws Exception {
     project = Project.nameKey("reindex-project-test");
     try (ServerContext ctx = startServer()) {
-      configureIndex(ctx.getInjector());
+      createAllIndexes(ctx.getInjector());
       GerritApi gApi = ctx.getInjector().getInstance(GerritApi.class);
       gApi.projects().create(project.get());
 
diff --git a/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java b/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
index f23cc10..0632241 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/ElasticReindexIT.java
@@ -14,23 +14,15 @@
 
 package com.google.gerrit.acceptance.pgm;
 
-import static com.google.gerrit.elasticsearch.ElasticTestUtils.createAllIndexes;
 import static com.google.gerrit.elasticsearch.ElasticTestUtils.getConfig;
 
 import com.google.gerrit.elasticsearch.ElasticVersion;
 import com.google.gerrit.testing.ConfigSuite;
-import com.google.inject.Injector;
 import org.eclipse.jgit.lib.Config;
 
 public class ElasticReindexIT extends AbstractReindexTests {
-
   @ConfigSuite.Default
   public static Config elasticsearchV7() {
     return getConfig(ElasticVersion.V7_8);
   }
-
-  @Override
-  public void configureIndex(Injector injector) {
-    createAllIndexes(injector);
-  }
 }
diff --git a/javatests/com/google/gerrit/acceptance/pgm/ReindexIT.java b/javatests/com/google/gerrit/acceptance/pgm/LuceneReindexIT.java
similarity index 68%
rename from javatests/com/google/gerrit/acceptance/pgm/ReindexIT.java
rename to javatests/com/google/gerrit/acceptance/pgm/LuceneReindexIT.java
index 223851e..e630bca 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/ReindexIT.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/LuceneReindexIT.java
@@ -14,9 +14,14 @@
 
 package com.google.gerrit.acceptance.pgm;
 
-import com.google.inject.Injector;
+import com.google.gerrit.testing.ConfigSuite;
+import org.eclipse.jgit.lib.Config;
 
-public class ReindexIT extends AbstractReindexTests {
-  @Override
-  public void configureIndex(Injector injector) {}
+public class LuceneReindexIT extends AbstractReindexTests {
+  @ConfigSuite.Default
+  public static Config luceneConfig() {
+    Config cfg = new Config();
+    cfg.setString("index", null, "type", "lucene");
+    return cfg;
+  }
 }
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
index 03e4bfb..4b45476 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.acceptance.rest.change;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.block;
 import static com.google.gerrit.extensions.restapi.testing.AttentionSetUpdateSubject.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 
@@ -32,23 +33,29 @@
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
 import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.AccountGroup;
 import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.AttentionSetUpdate.Operation;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.LabelId;
 import com.google.gerrit.entities.Patch;
+import com.google.gerrit.entities.Permission;
 import com.google.gerrit.extensions.api.changes.AttentionSetInput;
 import com.google.gerrit.extensions.api.changes.DeleteReviewerInput;
 import com.google.gerrit.extensions.api.changes.HashtagsInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.ReviewerInput;
+import com.google.gerrit.extensions.api.groups.GroupInput;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.EmailStrategy;
 import com.google.gerrit.extensions.client.ReviewerState;
 import com.google.gerrit.extensions.client.Side;
+import com.google.gerrit.extensions.common.GroupInfo;
+import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.server.account.ServiceUserClassifier;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -82,6 +89,7 @@
   @Inject private FakeEmailSender email;
   @Inject private TestCommentHelper testCommentHelper;
   @Inject private Provider<InternalChangeQuery> changeQueryProvider;
+  @Inject private ProjectOperations projectOperations;
 
   /** Simulates a fake clock. Uses second granularity. */
   private static class FakeClock implements LongSupplier {
@@ -1835,6 +1843,44 @@
     assertThat(attentionSet).hasReasonThat().isEqualTo("Their vote was deleted");
   }
 
+  @Test
+  public void accountsWithNoReadPermissionIgnoredOnReply() throws Exception {
+    // Create a group with user.
+    GroupInput groupInput = new GroupInput();
+    groupInput.name = name("User");
+    groupInput.members = ImmutableList.of(String.valueOf(user.id()));
+    GroupInfo group = gApi.groups().create(groupInput).get();
+
+    PushOneCommit.Result r = createChange();
+    gApi.changes().id(r.getChangeId()).addReviewer(user.email());
+
+    // remove read permission for user.
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref("refs/*").group(AccountGroup.uuid(group.id)))
+        .update();
+
+    // removing user without permissions from attention set is allowed on reply.
+    gApi.changes()
+        .id(r.getChangeId())
+        .current()
+        .review(new ReviewInput().removeUserFromAttentionSet(user.email(), "reason"));
+
+    // Add user to attention throws an exception.
+    assertThrows(
+        AuthException.class,
+        () -> change(r).addToAttentionSet(new AttentionSetInput(user.email(), "reason")));
+
+    // Add user to attention set is ignored on reply.
+    gApi.changes()
+        .id(r.getChangeId())
+        .current()
+        .review(new ReviewInput().addUserToAttentionSet(user.email(), "reason"));
+    assertThat(Iterables.getOnlyElement(getAttentionSetUpdatesForUser(r, user)).operation())
+        .isEqualTo(Operation.REMOVE);
+  }
+
   private List<AttentionSetUpdate> getAttentionSetUpdatesForUser(
       PushOneCommit.Result r, TestAccount account) {
     return getAttentionSetUpdates(r.getChange().getId()).stream()
diff --git a/javatests/com/google/gerrit/acceptance/server/change/ConsistencyCheckerIT.java b/javatests/com/google/gerrit/acceptance/server/change/ConsistencyCheckerIT.java
index e39f967..9d821b7 100644
--- a/javatests/com/google/gerrit/acceptance/server/change/ConsistencyCheckerIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/change/ConsistencyCheckerIT.java
@@ -257,7 +257,6 @@
             + "Groups: "
             + rev
             + "\n");
-    indexer.index(c.getProject(), c.getId());
     ChangeNotes notes = changeNotesFactory.create(c.getProject(), c.getId());
 
     FixInput fix = new FixInput();
@@ -817,8 +816,6 @@
             + "Subject: "
             + subject
             + "\n");
-    indexer.index(c.getProject(), c.getId());
-
     return ps;
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/index/DefaultIndexBindingIT.java b/javatests/com/google/gerrit/acceptance/testsuite/index/DefaultIndexBindingIT.java
new file mode 100644
index 0000000..f5e4e09
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/testsuite/index/DefaultIndexBindingIT.java
@@ -0,0 +1,51 @@
+// Copyright (C) 2021 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.acceptance.testsuite.index;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.index.IndexType;
+import com.google.gerrit.index.testing.AbstractFakeIndex;
+import com.google.gerrit.server.index.change.ChangeIndexCollection;
+import javax.inject.Inject;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+/** Test to check that the expected index backend was bound depending on sys/env properties. */
+public class DefaultIndexBindingIT extends AbstractDaemonTest {
+
+  @Inject private ChangeIndexCollection changeIndex;
+
+  private static String propertyBeforeTest;
+
+  @BeforeClass
+  public static void setup() {
+    propertyBeforeTest = System.getProperty(IndexType.SYS_PROP);
+    System.setProperty(IndexType.SYS_PROP, "");
+  }
+
+  @AfterClass
+  public static void teardown() {
+    System.setProperty(IndexType.SYS_PROP, propertyBeforeTest);
+  }
+
+  @Test
+  public void fakeIsBoundByDefault() throws Exception {
+    assertThat(System.getProperty(IndexType.SYS_PROP)).isEmpty();
+    assertThat(changeIndex.getSearchIndex()).isInstanceOf(AbstractFakeIndex.FakeChangeIndex.class);
+  }
+}
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/index/FakeIndexBindingIT.java b/javatests/com/google/gerrit/acceptance/testsuite/index/FakeIndexBindingIT.java
new file mode 100644
index 0000000..4122426
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/testsuite/index/FakeIndexBindingIT.java
@@ -0,0 +1,51 @@
+// Copyright (C) 2021 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.acceptance.testsuite.index;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.index.IndexType;
+import com.google.gerrit.index.testing.AbstractFakeIndex;
+import com.google.gerrit.server.index.change.ChangeIndexCollection;
+import javax.inject.Inject;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+/** Test to check that the expected index backend was bound depending on sys/env properties. */
+public class FakeIndexBindingIT extends AbstractDaemonTest {
+
+  @Inject private ChangeIndexCollection changeIndex;
+
+  private static String propertyBeforeTest;
+
+  @BeforeClass
+  public static void setup() {
+    propertyBeforeTest = System.getProperty(IndexType.SYS_PROP);
+    System.setProperty(IndexType.SYS_PROP, "fake");
+  }
+
+  @AfterClass
+  public static void teardown() {
+    System.setProperty(IndexType.SYS_PROP, propertyBeforeTest);
+  }
+
+  @Test
+  public void fakeIsBoundWhenConfigured() throws Exception {
+    assertThat(System.getProperty(IndexType.SYS_PROP)).isEqualTo("fake");
+    assertThat(changeIndex.getSearchIndex()).isInstanceOf(AbstractFakeIndex.FakeChangeIndex.class);
+  }
+}
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/index/LuceneIndexBindingIT.java b/javatests/com/google/gerrit/acceptance/testsuite/index/LuceneIndexBindingIT.java
new file mode 100644
index 0000000..31e31fd
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/testsuite/index/LuceneIndexBindingIT.java
@@ -0,0 +1,51 @@
+// Copyright (C) 2021 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.acceptance.testsuite.index;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.index.IndexType;
+import com.google.gerrit.lucene.LuceneChangeIndex;
+import com.google.gerrit.server.index.change.ChangeIndexCollection;
+import javax.inject.Inject;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+/** Test to check that the expected index backend was bound depending on sys/env properties. */
+public class LuceneIndexBindingIT extends AbstractDaemonTest {
+
+  @Inject private ChangeIndexCollection changeIndex;
+
+  private static String propertyBeforeTest;
+
+  @BeforeClass
+  public static void setup() {
+    propertyBeforeTest = System.getProperty(IndexType.SYS_PROP);
+    System.setProperty(IndexType.SYS_PROP, "lucene");
+  }
+
+  @AfterClass
+  public static void teardown() {
+    System.setProperty(IndexType.SYS_PROP, propertyBeforeTest);
+  }
+
+  @Test
+  public void luceneIsBoundWhenConfigured() throws Exception {
+    assertThat(System.getProperty(IndexType.SYS_PROP)).isEqualTo("lucene");
+    assertThat(changeIndex.getSearchIndex()).isInstanceOf(LuceneChangeIndex.class);
+  }
+}
diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index 3c10fbc..1f29f45 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
@@ -1007,6 +1007,7 @@
     changes.put(-1, reviewMinus1Change);
     changes.put(-2, reviewMinus2Change);
 
+    assertQuery("label:Code-Review=MIN", reviewMinus2Change);
     assertQuery("label:Code-Review=-2", reviewMinus2Change);
     assertQuery("label:Code-Review-2", reviewMinus2Change);
     assertQuery("label:Code-Review=-1", reviewMinus1Change);
@@ -1018,6 +1019,13 @@
     assertQuery("label:Code-Review=+2", reviewPlus2Change);
     assertQuery("label:Code-Review=2", reviewPlus2Change);
     assertQuery("label:Code-Review+2", reviewPlus2Change);
+    assertQuery("label:Code-Review=MAX", reviewPlus2Change);
+    assertQuery(
+        "label:Code-Review=ANY",
+        reviewPlus2Change,
+        reviewPlus1Change,
+        reviewMinus1Change,
+        reviewMinus2Change);
 
     assertQuery("label:Code-Review>-3", codeReviewInRange(changes, -2, 2));
     assertQuery("label:Code-Review>=-2", codeReviewInRange(changes, -2, 2));
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
index 23c0e14..9dcb67e 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
@@ -677,7 +677,8 @@
     patchRange?: PatchRange,
     file?: NormalizedFileInfo
   ) {
-    const draftCount = changeComments?.computeDraftCountForFile(
+    if (changeComments === undefined) return '';
+    const draftCount = changeComments.computeDraftCountForFile(
       patchRange,
       file
     );
@@ -693,7 +694,8 @@
     patchRange?: PatchRange,
     file?: NormalizedFileInfo
   ) {
-    const draftCount = changeComments?.computeDraftCountForFile(
+    if (changeComments === undefined) return '';
+    const draftCount = changeComments.computeDraftCountForFile(
       patchRange,
       file
     );
diff --git a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
index d341083..fae624e 100644
--- a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
@@ -90,9 +90,9 @@
  */
 function computeThreads(
   message: CombinedMessage,
-  changeComments: ChangeComments
+  changeComments?: ChangeComments
 ): CommentThread[] {
-  if (message._index === undefined) {
+  if (message._index === undefined || changeComments === undefined) {
     return [];
   }
   const messageId = getMessageId(message);
@@ -369,7 +369,7 @@
     return combinedMessages;
   }
 
-  getCommentThreads(message: CombinedMessage, changeComments: ChangeComments) {
+  getCommentThreads(message: CombinedMessage, changeComments?: ChangeComments) {
     return computeThreads(message, changeComments);
   }
 
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
index 6178e7a..4381a59 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
@@ -31,6 +31,7 @@
 import {hasOwnProperty} from '../../../utils/common-util';
 import {ProjectWatchInfo} from '../../../types/common';
 import {appContext} from '../../../services/app-context';
+import {IronInputElement} from '@polymer/iron-input';
 
 const NOTIFICATION_TYPES = [
   {name: 'Changes', key: 'notify_new_changes'},
@@ -43,9 +44,11 @@
 export interface GrWatchedProjectsEditor {
   $: {
     newFilter: HTMLInputElement;
+    newFilterInput: IronInputElement;
     newProject: GrAutocomplete;
   };
 }
+
 @customElement('gr-watched-projects-editor')
 export class GrWatchedProjectsEditor extends PolymerElement {
   static get template() {
@@ -62,7 +65,7 @@
   _projectsToRemove: ProjectWatchInfo[] = [];
 
   @property({type: Object})
-  _query?: AutocompleteQuery;
+  _query: AutocompleteQuery;
 
   private readonly restApiService = appContext.restApiService;
 
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
index edc8fb2..fb65a03 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
@@ -102,13 +102,13 @@
           </th>
           <th colspan$="[[_getTypeCount()]]">
             <iron-input
+              id="newFilterInput"
               class="newFilterInput"
               placeholder="branch:name, or other search expression"
             >
               <input
                 id="newFilter"
                 class="newFilterInput"
-                is="iron-input"
                 placeholder="branch:name, or other search expression"
               />
             </iron-input>
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
similarity index 76%
rename from polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js
rename to polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
index aac8995..cb4b86d 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
@@ -15,14 +15,18 @@
  * limitations under the License.
  */
 
-import '../../../test/common-test-setup-karma.js';
-import './gr-watched-projects-editor.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import '../../../test/common-test-setup-karma';
+import './gr-watched-projects-editor';
+import {GrWatchedProjectsEditor} from './gr-watched-projects-editor';
+import {stubRestApi} from '../../../test/test-utils';
+import {ProjectWatchInfo} from '../../../types/common';
+import {queryAll, queryAndAssert} from '../../../test/test-utils';
+import * as MockInteractions from '@polymer/iron-test-helpers/mock-interactions';
 
 const basicFixture = fixtureFromElement('gr-watched-projects-editor');
 
 suite('gr-watched-projects-editor tests', () => {
-  let element;
+  let element: GrWatchedProjectsEditor;
 
   setup(done => {
     const projects = [
@@ -30,29 +34,34 @@
         project: 'project a',
         notify_submitted_changes: true,
         notify_abandoned_changes: true,
-      }, {
+      },
+      {
         project: 'project b',
         filter: 'filter 1',
         notify_new_changes: true,
-      }, {
+      },
+      {
         project: 'project b',
         filter: 'filter 2',
-      }, {
+      },
+      {
         project: 'project c',
         notify_new_changes: true,
         notify_new_patch_sets: true,
         notify_all_comments: true,
       },
-    ];
+    ] as ProjectWatchInfo[];
 
     stubRestApi('getWatchedProjects').returns(Promise.resolve(projects));
     stubRestApi('getSuggestedProjects').callsFake(input => {
       if (input.startsWith('th')) {
-        return Promise.resolve({'the project': {
-          id: 'the project',
-          state: 'ACTIVE',
-          web_links: [],
-        }});
+        return Promise.resolve({
+          'the project': {
+            id: 'the project',
+            state: 'ACTIVE',
+            web_links: [],
+          },
+        });
       } else {
         return Promise.resolve({});
       }
@@ -60,18 +69,18 @@
 
     element = basicFixture.instantiate();
 
-    element.loadData().then(() => { flush(done); });
+    element.loadData().then(() => {
+      flush(done);
+    });
   });
 
   test('renders', () => {
-    const rows = element.shadowRoot
-        .querySelector('table').querySelectorAll('tbody tr');
+    const rows = queryAndAssert(element, 'table').querySelectorAll('tbody tr');
     assert.equal(rows.length, 4);
 
-    function getKeysOfRow(row) {
-      const boxes = rows[row].querySelectorAll('input[checked]');
-      return Array.prototype.map.call(boxes,
-          e => e.getAttribute('data-key'));
+    function getKeysOfRow(row: number) {
+      const boxes = queryAll(rows[row], 'input[checked]');
+      return Array.prototype.map.call(boxes, e => e.getAttribute('data-key'));
     }
 
     let checkedKeys = getKeysOfRow(0);
@@ -157,41 +166,44 @@
   test('_handleAddProject', () => {
     element.$.newProject.value = 'project d';
     element.$.newProject.setText('project d');
-    element.$.newFilter.bindValue = '';
+    element.$.newFilterInput.bindValue = '';
 
     element._handleAddProject();
 
-    assert.equal(element._projects.length, 5);
-    assert.equal(element._projects[4].project, 'project d');
-    assert.isNotOk(element._projects[4].filter);
-    assert.isTrue(element._projects[4]._is_local);
+    const projects = element._projects!;
+    assert.equal(projects.length, 5);
+    assert.equal(projects[4].project, 'project d');
+    assert.isNotOk(projects[4].filter);
+    assert.isTrue(projects[4]._is_local);
   });
 
   test('_handleAddProject with invalid inputs', () => {
     element.$.newProject.value = 'project b';
     element.$.newProject.setText('project b');
-    element.$.newFilter.bindValue = 'filter 1';
+    element.$.newFilterInput.bindValue = 'filter 1';
     element.$.newFilter.value = 'filter 1';
 
     element._handleAddProject();
 
-    assert.equal(element._projects.length, 4);
+    assert.equal(element._projects!.length, 4);
   });
 
   test('_handleRemoveProject', () => {
-    assert.equal(element._projectsToRemove, 0);
-    const button = element.shadowRoot
-        .querySelector('table tbody tr:nth-child(2) gr-button');
+    assert.deepEqual(element._projectsToRemove, []);
+
+    const button = queryAndAssert(
+      element,
+      'table tbody tr:nth-child(2) gr-button'
+    );
     MockInteractions.tap(button);
 
     flush();
 
-    const rows = element.shadowRoot
-        .querySelector('table tbody').querySelectorAll('tr');
+    const rows = queryAndAssert(element, 'table tbody').querySelectorAll('tr');
+
     assert.equal(rows.length, 3);
 
     assert.equal(element._projectsToRemove.length, 1);
     assert.equal(element._projectsToRemove[0].project, 'project b');
   });
 });
-
diff --git a/polygerrit-ui/app/node_modules_licenses/licenses.ts b/polygerrit-ui/app/node_modules_licenses/licenses.ts
index f04e224..bcdab0e 100644
--- a/polygerrit-ui/app/node_modules_licenses/licenses.ts
+++ b/polygerrit-ui/app/node_modules_licenses/licenses.ts
@@ -405,6 +405,14 @@
       packageLicenseFile: "LICENSE",
     }
   },
+  {
+    name: "immer",
+    license: {
+      name: "immer",
+      type: LicenseTypes.Mit,
+      packageLicenseFile: "LICENSE",
+    }
+  }
 ];
 
 export default packages;
diff --git a/polygerrit-ui/app/package.json b/polygerrit-ui/app/package.json
index 4e18e47..d26dc97 100644
--- a/polygerrit-ui/app/package.json
+++ b/polygerrit-ui/app/package.json
@@ -37,6 +37,7 @@
     "@webcomponents/webcomponentsjs": "^1.3.3",
     "ba-linkify": "file:../../lib/ba-linkify/src/",
     "codemirror-minified": "^5.62.0",
+    "immer": "^9.0.5",
     "lit-element": "^2.5.1",
     "page": "^1.11.6",
     "polymer-bridges": "file:../../polymer-bridges/",
diff --git a/polygerrit-ui/app/services/comments/comments-model.ts b/polygerrit-ui/app/services/comments/comments-model.ts
index 87f42c1..b26ec9b 100644
--- a/polygerrit-ui/app/services/comments/comments-model.ts
+++ b/polygerrit-ui/app/services/comments/comments-model.ts
@@ -130,6 +130,7 @@
     d => d.__draftID === draft.__draftID || d.id === draft.id
   );
   if (index === -1) return;
-  drafts[draft.path] = [...drafts[draft.path]].splice(index, 1);
+  drafts[draft.path] = [...drafts[draft.path]];
+  drafts[draft.path].splice(index, 1);
   privateState$.next(nextState);
 }
diff --git a/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts b/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
index 2cc6f41..0df7d12 100644
--- a/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
+++ b/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
@@ -419,7 +419,10 @@
       eventInfo.inBackgroundTab = isInBackgroundTab;
     }
 
-    if (this._flagsService.enabledExperiments.length) {
+    if (
+      name === Timing.APP_STARTED &&
+      this._flagsService.enabledExperiments.length
+    ) {
       eventInfo.enabledExperiments = JSON.stringify(
         this._flagsService.enabledExperiments
       );
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index 826794e..0f2608e 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -984,6 +984,7 @@
   notify_all_comments?: boolean;
   notify_submitted_changes?: boolean;
   notify_abandoned_changes?: boolean;
+  _is_local?: boolean; // Added manually
 }
 /**
  * The DeleteDraftCommentsInput entity contains information specifying a set of draft comments that should be deleted
diff --git a/polygerrit-ui/app/yarn.lock b/polygerrit-ui/app/yarn.lock
index d8657f7..4fb98dd 100644
--- a/polygerrit-ui/app/yarn.lock
+++ b/polygerrit-ui/app/yarn.lock
@@ -600,6 +600,11 @@
     agent-base "6"
     debug "4"
 
+immer@^9.0.5:
+  version "9.0.5"
+  resolved "https://registry.yarnpkg.com/immer/-/immer-9.0.5.tgz#a7154f34fe7064f15f00554cc94c66cc0bf453ec"
+  integrity sha512-2WuIehr2y4lmYz9gaQzetPR2ECniCifk4ORaQbU3g5EalLt+0IVTosEPJ5BoYl/75ky2mivzdRzV8wWgQGOSYQ==
+
 inflight@^1.0.4:
   version "1.0.6"
   resolved "https://registry.yarnpkg.com/inflight/-/inflight-1.0.6.tgz#49bd6331d7d02d0c09bc910a1075ba8165b56df9"