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gerrit/gerrit/2e0f04f77a7be2d9f6fc3bdd4c75f90da8c408a4^1..2e0f04f77a7be2d9f6fc3bdd4c75f90da8c408a4/.
commit
2e0f04f77a7be2d9f6fc3bdd4c75f90da8c408a4
[log]
author
Matthias Sohn <matthias.sohn@gmail.com>
Wed Mar 20 20:00:41 2024 +0000
committer
Gerrit Code Review <noreply-gerritcodereview@google.com>
Wed Mar 20 20:00:41 2024 +0000
tree
bb7c1139fa8372b68a6e73b5c1fba689a0720c9a
parent
426cf1fbbd0df6d89cd4b4f3ddec4d4952a880ee [diff]
parent
8d9e42b24ce6882e75a1fc23cf23572d15167f8c [diff]
Merge changes I5a30dad3,I1fc60d2a,I3c5e7c15

* changes:
  Add REST endpoint for reindexing an index version
  Add REST API for getting info about indexes
  Optionally allow to reuse existing documents during reindexing

diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index cf2f2d9..9ce2eee 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt

@@ -3488,6 +3488,21 @@
 Excluded projects can later be reindexed by for example using the
 link:cmd-index-changes-in-project.html[index changes in project command].
 
+[[index.reuseExistingDocuments]]index.reuseExistingDocuments::
++
+Whether to reuse index documents that already exist during reindexing.
++
+Currently, only supported by the changes index.
++
+This feature is useful, if the Gerrit server has to be restarted
+during an ongoing index online upgrade, since this would cause
+a complete reindexing otherwise that might take an extensive time.
++
+Each existing document in the index will be checked for staleness
+and reindexed if found to be stale.
++
+Defaults to false.
+
 [[index.paginationType]]index.paginationType::
 +
 The pagination type to use when index queries are repeated to

diff --git a/Documentation/rest-api-config.txt b/Documentation/rest-api-config.txt
index aa88141..d8ff80a 100644
--- a/Documentation/rest-api-config.txt
+++ b/Documentation/rest-api-config.txt

@@ -1444,8 +1444,8 @@
   Content-Type: application/json; charset=UTF-8
 
   )]}'
-  {
-    "accounts": {
+  [
+    {
       "name": "accounts",
       "versions": {
         "13": {
@@ -1454,7 +1454,7 @@
         }
       }
     },
-    "changes": {
+    {
       "name": "changes",
       "versions": {
         "83": {
@@ -1467,7 +1467,7 @@
         }
       }
     },
-    "groups": {
+    {
       "name": "groups",
       "versions": {
         "10": {
@@ -1476,7 +1476,7 @@
         }
       }
     },
-    "projects": {
+    {
       "name": "projects",
       "versions": {
         "8": {
@@ -1485,33 +1485,125 @@
         }
       }
     }
+  [
+----
+
+=== Get Index
+--
+'GET /config/server/indexes/changes'
+--
+
+Get an index used by Gerrit. It provides details about the index versions, which
+index version is used to search and which versions are written to.
+
+.Request
+----
+  'GET /config/server/indexes/changes'
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "name": "changes",
+    "versions": {
+      "83": {
+        "write": true,
+        "search": true
+      },
+      "84": {
+        "write": true,
+        "search": false
+      }
+    }
+  }
+----
+
+=== List Index Versions
+--
+'GET /config/server/indexes/changes/versions'
+--
+
+Lists versions of an index used by Gerrit.
+
+.Request
+----
+  'GET /config/server/indexes/changes/versions'
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "83": {
+      "write": true,
+      "search": true
+    },
+    "84": {
+      "write": true,
+      "search": false
+    }
+  }
+----
+
+=== Get Index Version
+--
+'GET /config/server/indexes/changes/versions/85'
+--
+
+Get info about one version of an index used by Gerrit.
+
+.Request
+----
+  'GET /config/server/indexes/changes/versions/84'
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "write": true,
+    "search": false
   }
 ----
 
 [[snapshot-index]]
 === Create Index Snapshot
 
-This endpoint allows Gerrit admins to create a snapshot of an index.
-This snapshot can be used as a backup of the index.
+These endpoints allow Gerrit admins to create index snapshots.
+Created snapshots can be used as a backup of the index.
 
-A snapshot of all versions of an index can be created by just using
-the name of the index, e.g. `changes`. Only snapshots of indexes that
-Gerrit currently writes to can be created. An index version can be
-selected by using e.g. `changes~84`. Snapshots of all indexes can be
-created by using `all` instead of an index name.
+It is possible to create a snapshot of all indexes, snapshot of one index or
+snapshot of one index version.
+
+The snapshots will be stored on the server at `$SITE/index/snapshots/$ID`.
+The `$ID` can be optionally provided in link:#snapshot-index-input[SnapshotIndex.Input]
+or will default to the current local time in ISO8601 format.
+
+Only snapshots of indexes that Gerrit currently writes to can be created.
 
 Note, that the creation of multiple snapshots, e.g. of different index
 versions, is not atomic. If a consistent state over multiple indexes is
 required, the server has to be put into read-only mode before creating
 the snapshot.
 
-The snapshots will be stored on the server at `$SITE/index/snapshots/$ID`.
-The `$ID` can be optionally provided in link:#snapshot-index-input[SnapshotIndex.Input]
-or will default to the current local time in ISO8601 format.
+==== Create Snapshot of All Indexes
+--
+'POST /config/server/snapshot.indexes HTTP/1.0'
+--
 
 .Request
 ----
-  PUT /config/server/indexes/all/snapshot HTTP/1.0
+  POST /config/server/snapshot.indexes HTTP/1.0
   Content-Type: application/json; charset=UTF-8
 
   {
@@ -1530,9 +1622,16 @@
   }
 ----
 
+==== Create Snapshot of one Index
+--
+'POST /config/server/indexes/link:#index-name[\{index-name\}]/snapshot'
+--
+
+This creates a snapshot of all write index versions of the specified index.
+
 .Request
 ----
-  PUT /config/server/indexes/accounts~13/snapshot HTTP/1.0
+  POST /config/server/indexes/accounts/snapshot HTTP/1.0
   Content-Type: application/json; charset=UTF-8
 
   {
@@ -1551,6 +1650,61 @@
   }
 ----
 
+==== Create Snapshot of one Index Version
+--
+'POST /config/server/indexes/link:#index-name[\{index-name\}]/versions/#index-version[\{index-version\}]/snapshot'
+--
+
+This creates a snapshot of one index version of the specified index.
+
+.Request
+----
+  POST /config/server/indexes/changes/versions/84/snapshot HTTP/1.0
+  Content-Type: application/json; charset=UTF-8
+
+  {
+    "id": "snapshot-1"
+  }
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "id": "snapshot-1"
+  }
+----
+
+=== Reindex an Index Version
+--
+'POST /config/server/indexes/link:#index-name[\{index-name\}]/versions/#index-version[\{index-version\}]/reindex'
+--
+
+This endpoint allows to trigger background reindexing of an index version.  It is
+also supported to specify whether to reuse existing up-to-date (non-stale) index
+documents.
+
+.Request
+----
+  POST /config/server/indexes/changes/versions/84/reindex HTTP/1.0
+  Content-Type: application/json; charset=UTF-8
+
+  {
+    "reuse": "true"
+  }
+----
+
+.Response
+----
+  HTTP/1.1 202 Accepted
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+----
+
 [[ids]]
 == IDs
 
@@ -1568,6 +1722,13 @@
 === \{task-id\}
 The ID of the task (hex string).
 
+[[index-name]]
+=== \{index-name\}
+The name of the index. Can be any of: "accounts", "changes", "groups", "projects".
+
+[[index-version]]
+=== \{index-version\}
+The version of the index. This is an integer.
 
 [[json-entities]]
 == JSON Entities

diff --git a/java/com/google/gerrit/acceptance/ChangeIndexedCounter.java b/java/com/google/gerrit/acceptance/ChangeIndexedCounter.java
index 5991646..98287c8 100644
--- a/java/com/google/gerrit/acceptance/ChangeIndexedCounter.java
+++ b/java/com/google/gerrit/acceptance/ChangeIndexedCounter.java

@@ -41,6 +41,10 @@
     return countsByChange.get(info._number);
   }
 
+  public long getTotalCount() {
+    return countsByChange.asMap().values().stream().reduce(0L, Long::sum);
+  }
+
   public void assertReindexOf(ChangeInfo info) {
     assertReindexOf(info, 1);
   }

diff --git a/java/com/google/gerrit/index/IndexDefinition.java b/java/com/google/gerrit/index/IndexDefinition.java
index f283bf1..cbcb34e 100644
--- a/java/com/google/gerrit/index/IndexDefinition.java
+++ b/java/com/google/gerrit/index/IndexDefinition.java

@@ -67,7 +67,11 @@
   }
 
   @Nullable
-  public final SiteIndexer<K, V, I> getSiteIndexer() {
+  public SiteIndexer<K, V, I> getSiteIndexer() {
+    return siteIndexer;
+  }
+
+  public SiteIndexer<K, V, I> getSiteIndexer(boolean reuseExistingDocuments) {
     return siteIndexer;
   }
 }

diff --git a/java/com/google/gerrit/index/testing/FakeIndexVersionManager.java b/java/com/google/gerrit/index/testing/FakeIndexVersionManager.java
index 5044e38..40d51fd 100644
--- a/java/com/google/gerrit/index/testing/FakeIndexVersionManager.java
+++ b/java/com/google/gerrit/index/testing/FakeIndexVersionManager.java

@@ -40,7 +40,12 @@
       SitePaths sitePaths,
       PluginSetContext<OnlineUpgradeListener> listeners,
       Collection<IndexDefinition<?, ?, ?>> defs) {
-    super(sitePaths, listeners, defs, VersionManager.getOnlineUpgrade(cfg));
+    super(
+        sitePaths,
+        listeners,
+        defs,
+        VersionManager.getOnlineUpgrade(cfg),
+        cfg.getBoolean("index", "reuseExistingDocuments", false));
   }
 
   @Override

diff --git a/java/com/google/gerrit/lucene/LuceneVersionManager.java b/java/com/google/gerrit/lucene/LuceneVersionManager.java
index f3ba73d..265d3e0 100644
--- a/java/com/google/gerrit/lucene/LuceneVersionManager.java
+++ b/java/com/google/gerrit/lucene/LuceneVersionManager.java

@@ -49,7 +49,12 @@
       SitePaths sitePaths,
       PluginSetContext<OnlineUpgradeListener> listeners,
       Collection<IndexDefinition<?, ?, ?>> defs) {
-    super(sitePaths, listeners, defs, VersionManager.getOnlineUpgrade(cfg));
+    super(
+        sitePaths,
+        listeners,
+        defs,
+        VersionManager.getOnlineUpgrade(cfg),
+        cfg.getBoolean("index", "reuseExistingDocuments", false));
   }
 
   @Override

diff --git a/java/com/google/gerrit/pgm/Reindex.java b/java/com/google/gerrit/pgm/Reindex.java
index 2ed2b76..e800d17 100644
--- a/java/com/google/gerrit/pgm/Reindex.java
+++ b/java/com/google/gerrit/pgm/Reindex.java

@@ -98,6 +98,8 @@
   @Option(name = "--build-bloom-filter", usage = "Build bloom filter for H2 disk caches.")
   private boolean buildBloomFilter;
 
+  private Boolean reuseExistingDocumentsOption;
+
   private Injector dbInjector;
   private Injector sysInjector;
   private Injector cfgInjector;
@@ -106,6 +108,11 @@
   @Inject private Collection<IndexDefinition<?, ?, ?>> indexDefs;
   @Inject private DynamicMap<Cache<?, ?>> cacheMap;
 
+  @Option(name = "--reuse", usage = "Reindex only when existing index entry is stale")
+  public void setReuseExistingDocuments(boolean value) {
+    reuseExistingDocumentsOption = value;
+  }
+
   @Override
   public int run() throws Exception {
     mustHaveValidSite();
@@ -258,9 +265,16 @@
     requireNonNull(
         index, () -> String.format("no active search index configured for %s", def.getName()));
     index.markReady(false);
-    index.deleteAll();
+    boolean reuseExistingDocuments =
+        reuseExistingDocumentsOption != null
+            ? reuseExistingDocumentsOption
+            : globalConfig.getBoolean("index", null, "reuseExistingDocuments", false);
 
-    SiteIndexer<K, V, I> siteIndexer = def.getSiteIndexer();
+    if (!reuseExistingDocuments) {
+      index.deleteAll();
+    }
+
+    SiteIndexer<K, V, I> siteIndexer = def.getSiteIndexer(reuseExistingDocuments);
     siteIndexer.setProgressOut(System.err);
     siteIndexer.setVerboseOut(verbose ? System.out : NullOutputStream.INSTANCE);
     SiteIndexer.Result result = siteIndexer.indexAll(index);

diff --git a/java/com/google/gerrit/server/config/IndexResource.java b/java/com/google/gerrit/server/config/IndexResource.java
index a65cc52..30d39c4 100644
--- a/java/com/google/gerrit/server/config/IndexResource.java
+++ b/java/com/google/gerrit/server/config/IndexResource.java

@@ -14,44 +14,21 @@
 
 package com.google.gerrit.server.config;
 
-import com.google.common.collect.ImmutableList;
-import com.google.gerrit.common.Nullable;
-import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestView;
 import com.google.gerrit.index.Index;
-import com.google.gerrit.index.IndexCollection;
+import com.google.gerrit.index.IndexDefinition;
 import com.google.inject.TypeLiteral;
-import java.util.Collection;
-import java.util.List;
 
 public class IndexResource extends ConfigResource {
   public static final TypeLiteral<RestView<IndexResource>> INDEX_KIND = new TypeLiteral<>() {};
 
-  private final ImmutableList<Index<?, ?>> indexes;
+  private IndexDefinition<?, ?, ?> def;
 
-  public IndexResource(IndexCollection<?, ?, ?> indexes, @Nullable Integer version)
-      throws ResourceNotFoundException {
-    if (version == null) {
-      this.indexes = ImmutableList.copyOf(indexes.getWriteIndexes());
-    } else {
-      Index<?, ?> index = indexes.getWriteIndex(version);
-      if (index == null) {
-        throw new ResourceNotFoundException(
-            String.format("Unknown index version requested: %d", version));
-      }
-      this.indexes = ImmutableList.of(index);
-    }
+  public IndexResource(IndexDefinition<?, ?, ?> def) {
+    this.def = def;
   }
 
-  public IndexResource(List<IndexCollection<?, ?, ?>> indexes) {
-    ImmutableList.Builder<Index<?, ?>> allIndexes = ImmutableList.builder();
-    for (IndexCollection<?, ?, ?> index : indexes) {
-      allIndexes.addAll(index.getWriteIndexes());
-    }
-    this.indexes = allIndexes.build();
-  }
-
-  public Collection<Index<?, ?>> getIndexes() {
-    return indexes;
+  public IndexDefinition<?, ?, ? extends Index<?, ?>> getIndexDefinition() {
+    return def;
   }
 }

diff --git a/java/com/google/gerrit/server/config/IndexVersionResource.java b/java/com/google/gerrit/server/config/IndexVersionResource.java
new file mode 100644
index 0000000..8ccb0b0
--- /dev/null
+++ b/java/com/google/gerrit/server/config/IndexVersionResource.java

@@ -0,0 +1,42 @@
+// Copyright (C) 2024 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.config;
+
+import com.google.gerrit.extensions.restapi.RestResource;
+import com.google.gerrit.extensions.restapi.RestView;
+import com.google.gerrit.index.Index;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.inject.TypeLiteral;
+
+public class IndexVersionResource implements RestResource {
+  public static final TypeLiteral<RestView<IndexVersionResource>> INDEX_VERSION_KIND =
+      new TypeLiteral<>() {};
+
+  private final IndexDefinition<?, ?, ?> def;
+  private final Index<?, ?> index;
+
+  public IndexVersionResource(IndexDefinition<?, ?, ?> def, Index<?, ?> index) {
+    this.def = def;
+    this.index = index;
+  }
+
+  public IndexDefinition<?, ?, ?> getIndexDefinition() {
+    return def;
+  }
+
+  public Index<?, ?> getIndex() {
+    return index;
+  }
+}

diff --git a/java/com/google/gerrit/server/index/IndexModule.java b/java/com/google/gerrit/server/index/IndexModule.java
index 96870ea..c048e3c 100644
--- a/java/com/google/gerrit/server/index/IndexModule.java
+++ b/java/com/google/gerrit/server/index/IndexModule.java

@@ -25,6 +25,7 @@
 import com.google.common.util.concurrent.MoreExecutors;
 import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.extensions.registration.DynamicSet;
+import com.google.gerrit.index.IndexConfig;
 import com.google.gerrit.index.IndexDefinition;
 import com.google.gerrit.index.IndexType;
 import com.google.gerrit.index.SchemaDefinitions;
@@ -34,6 +35,7 @@
 import com.google.gerrit.index.project.ProjectSchemaDefinitions;
 import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.MultiProgressMonitor;
 import com.google.gerrit.server.git.WorkQueue;
 import com.google.gerrit.server.index.account.AccountIndexCollection;
@@ -42,11 +44,13 @@
 import com.google.gerrit.server.index.account.AccountIndexer;
 import com.google.gerrit.server.index.account.AccountIndexerImpl;
 import com.google.gerrit.server.index.account.AccountSchemaDefinitions;
+import com.google.gerrit.server.index.change.AllChangesIndexer;
 import com.google.gerrit.server.index.change.ChangeIndexCollection;
 import com.google.gerrit.server.index.change.ChangeIndexDefinition;
 import com.google.gerrit.server.index.change.ChangeIndexRewriter;
 import com.google.gerrit.server.index.change.ChangeIndexer;
 import com.google.gerrit.server.index.change.ChangeSchemaDefinitions;
+import com.google.gerrit.server.index.change.StalenessChecker;
 import com.google.gerrit.server.index.group.GroupIndexCollection;
 import com.google.gerrit.server.index.group.GroupIndexDefinition;
 import com.google.gerrit.server.index.group.GroupIndexRewriter;
@@ -129,6 +133,8 @@
     bind(ChangeIndexCollection.class);
     listener().to(ChangeIndexCollection.class);
     factory(ChangeIndexer.Factory.class);
+    factory(StalenessChecker.Factory.class);
+    factory(AllChangesIndexer.Factory.class);
 
     bind(GroupIndexRewriter.class);
     // GroupIndexCollection is already bound very high up in SchemaModule.
@@ -255,6 +261,13 @@
     return MoreExecutors.listeningDecorator(workQueue.createQueue(threads, "Index-Batch", true));
   }
 
+  @Provides
+  @Singleton
+  StalenessChecker getChangeStalenessChecker(
+      ChangeIndexCollection indexes, GitRepositoryManager repoManager, IndexConfig indexConfig) {
+    return new StalenessChecker(indexes, repoManager, indexConfig);
+  }
+
   @Singleton
   private static class ShutdownIndexExecutors implements LifecycleListener {
     private final ListeningExecutorService interactiveExecutor;

diff --git a/java/com/google/gerrit/server/index/IndexVersionReindexer.java b/java/com/google/gerrit/server/index/IndexVersionReindexer.java
new file mode 100644
index 0000000..5d136e8
--- /dev/null
+++ b/java/com/google/gerrit/server/index/IndexVersionReindexer.java

@@ -0,0 +1,56 @@
+// Copyright (C) 2024 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.index;
+
+import static com.google.gerrit.server.git.QueueProvider.QueueType.BATCH;
+
+import com.google.common.flogger.FluentLogger;
+import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.index.Index;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.index.SiteIndexer;
+import com.google.inject.Inject;
+import java.util.concurrent.Future;
+
+public class IndexVersionReindexer {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private ListeningExecutorService executor;
+
+  @Inject
+  IndexVersionReindexer(@IndexExecutor(BATCH) ListeningExecutorService executor) {
+    this.executor = executor;
+  }
+
+  public <K, V, I extends Index<K, V>> Future<SiteIndexer.Result> reindex(
+      IndexDefinition<K, V, I> def, int version, boolean reuse) {
+    I index = def.getIndexCollection().getWriteIndex(version);
+    SiteIndexer<K, V, I> siteIndexer = def.getSiteIndexer(reuse);
+    return executor.submit(
+        () -> {
+          String name = def.getName();
+          logger.atInfo().log("Starting reindex of %s version %d", name, version);
+          SiteIndexer.Result result = siteIndexer.indexAll(index);
+          if (result.success()) {
+            logger.atInfo().log("Reindex %s version %s complete", name, version);
+          } else {
+            logger.atInfo().log(
+                "Reindex %s version %s failed. Successfully indexed %s, failed to index %s",
+                name, version, result.doneCount(), result.failedCount());
+          }
+          return result;
+        });
+  }
+}

diff --git a/java/com/google/gerrit/server/index/OnlineReindexer.java b/java/com/google/gerrit/server/index/OnlineReindexer.java
index eef394d..98abf46 100644
--- a/java/com/google/gerrit/server/index/OnlineReindexer.java
+++ b/java/com/google/gerrit/server/index/OnlineReindexer.java

@@ -42,18 +42,21 @@
   private final PluginSetContext<OnlineUpgradeListener> listeners;
   private I index;
   private final AtomicBoolean running = new AtomicBoolean();
+  private final boolean reuseExistingDocuments;
 
   public OnlineReindexer(
       IndexDefinition<K, V, I> def,
       int oldVersion,
       int newVersion,
-      PluginSetContext<OnlineUpgradeListener> listeners) {
+      PluginSetContext<OnlineUpgradeListener> listeners,
+      boolean reuseExistingDocuments) {
     this.name = def.getName();
     this.indexes = def.getIndexCollection();
     this.batchIndexer = def.getSiteIndexer();
     this.oldVersion = oldVersion;
     this.newVersion = newVersion;
     this.listeners = listeners;
+    this.reuseExistingDocuments = reuseExistingDocuments;
   }
 
   /** Starts the background process. */
@@ -106,7 +109,7 @@
         "Starting online reindex of %s from schema version %s to %s",
         name, version(indexes.getSearchIndex()), version(index));
 
-    if (oldVersion != newVersion) {
+    if (!reuseExistingDocuments && oldVersion != newVersion) {
       index.deleteAll();
     }
     SiteIndexer.Result result = batchIndexer.indexAll(index);

diff --git a/java/com/google/gerrit/server/index/VersionManager.java b/java/com/google/gerrit/server/index/VersionManager.java
index 39930a6..2c38caf 100644
--- a/java/com/google/gerrit/server/index/VersionManager.java
+++ b/java/com/google/gerrit/server/index/VersionManager.java

@@ -59,6 +59,7 @@
   }
 
   protected final boolean onlineUpgrade;
+  protected final boolean reuseExistingDocuments;
   protected final String runReindexMsg;
   protected final SitePaths sitePaths;
 
@@ -72,7 +73,8 @@
       SitePaths sitePaths,
       PluginSetContext<OnlineUpgradeListener> listeners,
       Collection<IndexDefinition<?, ?, ?>> defs,
-      boolean onlineUpgrade) {
+      boolean onlineUpgrade,
+      boolean reuseExistingDocuments) {
     this.sitePaths = sitePaths;
     this.listeners = listeners;
     this.defs = Maps.newHashMapWithExpectedSize(defs.size());
@@ -82,6 +84,7 @@
 
     this.reindexers = Maps.newHashMapWithExpectedSize(defs.size());
     this.onlineUpgrade = onlineUpgrade;
+    this.reuseExistingDocuments = reuseExistingDocuments;
     this.runReindexMsg =
         "No index versions for index '%s' ready; run java -jar "
             + sitePaths.gerrit_war.toAbsolutePath()
@@ -190,7 +193,7 @@
       if (!reindexers.containsKey(def.getName())) {
         int latest = write.get(0).version;
         OnlineReindexer<K, V, I> reindexer =
-            new OnlineReindexer<>(def, search.version, latest, listeners);
+            new OnlineReindexer<>(def, search.version, latest, listeners, reuseExistingDocuments);
         reindexers.put(def.getName(), reindexer);
       }
     }

diff --git a/java/com/google/gerrit/server/index/change/AllChangesIndexer.java b/java/com/google/gerrit/server/index/change/AllChangesIndexer.java
index 3935108..925f68d 100644
--- a/java/com/google/gerrit/server/index/change/AllChangesIndexer.java
+++ b/java/com/google/gerrit/server/index/change/AllChangesIndexer.java

@@ -43,7 +43,8 @@
 import com.google.gerrit.server.notedb.ChangeNotes.Factory.ChangeNotesResult;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.query.change.ChangeData;
-import com.google.inject.Inject;
+import com.google.inject.assistedinject.Assisted;
+import com.google.inject.assistedinject.AssistedInject;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
@@ -52,6 +53,7 @@
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
@@ -65,6 +67,13 @@
  */
 public class AllChangesIndexer extends SiteIndexer<Change.Id, ChangeData, ChangeIndex> {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  public interface Factory {
+    AllChangesIndexer create();
+
+    AllChangesIndexer create(boolean reuseExistingDocuments);
+  }
+
   private MultiProgressMonitor mpm;
   private VolatileTask doneTask;
   private Task failedTask;
@@ -84,25 +93,54 @@
   private final GitRepositoryManager repoManager;
   private final ListeningExecutorService executor;
   private final ChangeIndexer.Factory indexerFactory;
+  private final StalenessChecker.Factory stalenessCheckerFactory;
   private final ChangeNotes.Factory notesFactory;
   private final ProjectCache projectCache;
   private final Set<Project.NameKey> projectsToSkip;
+  private final boolean reuseExistingDocuments;
 
-  @Inject
+  @AssistedInject
   AllChangesIndexer(
       MultiProgressMonitor.Factory multiProgressMonitorFactory,
       ChangeData.Factory changeDataFactory,
       GitRepositoryManager repoManager,
       @IndexExecutor(BATCH) ListeningExecutorService executor,
       ChangeIndexer.Factory indexerFactory,
+      StalenessChecker.Factory stalenessCheckerFactory,
       ChangeNotes.Factory notesFactory,
       ProjectCache projectCache,
       @GerritServerConfig Config config) {
+    this(
+        multiProgressMonitorFactory,
+        changeDataFactory,
+        repoManager,
+        executor,
+        indexerFactory,
+        stalenessCheckerFactory,
+        notesFactory,
+        projectCache,
+        config,
+        config.getBoolean("index", null, "reuseExistingDocuments", false));
+  }
+
+  @AssistedInject
+  AllChangesIndexer(
+      MultiProgressMonitor.Factory multiProgressMonitorFactory,
+      ChangeData.Factory changeDataFactory,
+      GitRepositoryManager repoManager,
+      @IndexExecutor(BATCH) ListeningExecutorService executor,
+      ChangeIndexer.Factory indexerFactory,
+      StalenessChecker.Factory stalenessCheckerFactory,
+      ChangeNotes.Factory notesFactory,
+      ProjectCache projectCache,
+      @GerritServerConfig Config config,
+      @Assisted boolean reuseExistingDocuments) {
     this.multiProgressMonitorFactory = multiProgressMonitorFactory;
     this.changeDataFactory = changeDataFactory;
     this.repoManager = repoManager;
     this.executor = executor;
     this.indexerFactory = indexerFactory;
+    this.stalenessCheckerFactory = stalenessCheckerFactory;
     this.notesFactory = notesFactory;
     this.projectCache = projectCache;
     this.projectsToSkip =
@@ -110,6 +148,7 @@
             .stream()
             .map(p -> Project.NameKey.parse(p))
             .collect(Collectors.toSet());
+    this.reuseExistingDocuments = reuseExistingDocuments;
   }
 
   @AutoValue
@@ -218,20 +257,27 @@
   }
 
   private class ProjectSliceIndexer implements Callable<Void> {
-    private final ChangeIndexer indexer;
     private final ProjectSlice projectSlice;
     private final ProgressMonitor done;
     private final ProgressMonitor failed;
+    private final Consumer<ChangeData> indexAction;
 
     private ProjectSliceIndexer(
         ChangeIndexer indexer,
         ProjectSlice projectSlice,
         ProgressMonitor done,
         ProgressMonitor failed) {
-      this.indexer = indexer;
       this.projectSlice = projectSlice;
       this.done = done;
       this.failed = failed;
+      if (reuseExistingDocuments) {
+        indexAction =
+            cd -> {
+              var unused = indexer.reindexIfStale(cd);
+            };
+      } else {
+        indexAction = cd -> indexer.index(cd);
+      }
     }
 
     @Override
@@ -271,7 +317,7 @@
         return;
       }
       try {
-        indexer.index(changeDataFactory.create(r.notes()));
+        indexAction.accept(changeDataFactory.create(r.notes()));
         done.update(1);
         verboseWriter.format(
             "Reindexed change %d (project: %s)\n", r.id().get(), r.notes().getProjectName().get());
@@ -385,13 +431,15 @@
 
             for (int slice = 0; slice < slices; slice++) {
               ProjectSlice projectSlice = ProjectSlice.create(name, slice, slices, metaIdByChange);
+              ChangeIndexer indexer;
+              if (reuseExistingDocuments) {
+                indexer =
+                    indexerFactory.create(executor, index, stalenessCheckerFactory.create(index));
+              } else {
+                indexer = indexerFactory.create(executor, index);
+              }
               ListenableFuture<?> future =
-                  executor.submit(
-                      reindexProjectSlice(
-                          indexerFactory.create(executor, index),
-                          projectSlice,
-                          doneTask,
-                          failedTask));
+                  executor.submit(reindexProjectSlice(indexer, projectSlice, doneTask, failedTask));
               String description = "project " + name + " (" + slice + "/" + slices + ")";
               addErrorListener(future, description, projTask, ok);
               sliceIndexerFutures.add(future);

diff --git a/java/com/google/gerrit/server/index/change/ChangeIndexDefinition.java b/java/com/google/gerrit/server/index/change/ChangeIndexDefinition.java
index dde9d86..342796b 100644
--- a/java/com/google/gerrit/server/index/change/ChangeIndexDefinition.java
+++ b/java/com/google/gerrit/server/index/change/ChangeIndexDefinition.java

@@ -14,20 +14,34 @@
 
 package com.google.gerrit.server.index.change;
 
-import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.index.SiteIndexer;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.inject.Inject;
 
 /** Bundle of service classes that make up the change index. */
 public class ChangeIndexDefinition extends IndexDefinition<Change.Id, ChangeData, ChangeIndex> {
 
+  private final AllChangesIndexer.Factory allChangesIndexerFactory;
+
   @Inject
   ChangeIndexDefinition(
       ChangeIndexCollection indexCollection,
       ChangeIndex.Factory indexFactory,
-      @Nullable AllChangesIndexer allChangesIndexer) {
-    super(ChangeSchemaDefinitions.INSTANCE, indexCollection, indexFactory, allChangesIndexer);
+      AllChangesIndexer.Factory allChangesIndexerFactory) {
+    super(ChangeSchemaDefinitions.INSTANCE, indexCollection, indexFactory, null);
+    this.allChangesIndexerFactory = allChangesIndexerFactory;
+  }
+
+  @Override
+  public SiteIndexer<Change.Id, ChangeData, ChangeIndex> getSiteIndexer() {
+    return allChangesIndexerFactory.create();
+  }
+
+  @Override
+  public SiteIndexer<Change.Id, ChangeData, ChangeIndex> getSiteIndexer(
+      boolean reuseExistingDocuments) {
+    return allChangesIndexerFactory.create(reuseExistingDocuments);
   }
 }

diff --git a/java/com/google/gerrit/server/index/change/ChangeIndexer.java b/java/com/google/gerrit/server/index/change/ChangeIndexer.java
index 562f9c4..4ec390d 100644
--- a/java/com/google/gerrit/server/index/change/ChangeIndexer.java
+++ b/java/com/google/gerrit/server/index/change/ChangeIndexer.java

@@ -70,6 +70,9 @@
   public interface Factory {
     ChangeIndexer create(ListeningExecutorService executor, ChangeIndex index);
 
+    ChangeIndexer create(
+        ListeningExecutorService executor, ChangeIndex index, StalenessChecker stalenessChecker);
+
     ChangeIndexer create(ListeningExecutorService executor, ChangeIndexCollection indexes);
   }
 
@@ -121,6 +124,31 @@
       ChangeNotes.Factory notesFactory,
       ThreadLocalRequestContext context,
       PluginSetContext<ChangeIndexedListener> indexedListeners,
+      @IndexExecutor(BATCH) ListeningExecutorService batchExecutor,
+      IsFirstInsertForEntry isFirstInsertForEntry,
+      @Assisted ListeningExecutorService executor,
+      @Assisted ChangeIndex index,
+      @Assisted StalenessChecker stalenessChecker) {
+    this.executor = executor;
+    this.changeDataFactory = changeDataFactory;
+    this.notesFactory = notesFactory;
+    this.context = context;
+    this.indexedListeners = indexedListeners;
+    this.batchExecutor = batchExecutor;
+    this.autoReindexIfStale = autoReindexIfStale(cfg);
+    this.isFirstInsertForEntry = isFirstInsertForEntry;
+    this.index = index;
+    this.indexes = null;
+    this.stalenessChecker = stalenessChecker;
+  }
+
+  @AssistedInject
+  ChangeIndexer(
+      @GerritServerConfig Config cfg,
+      ChangeData.Factory changeDataFactory,
+      ChangeNotes.Factory notesFactory,
+      ThreadLocalRequestContext context,
+      PluginSetContext<ChangeIndexedListener> indexedListeners,
       StalenessChecker stalenessChecker,
       @IndexExecutor(BATCH) ListeningExecutorService batchExecutor,
       @Assisted ListeningExecutorService executor,
@@ -350,7 +378,7 @@
    * @param id ID of the change to index.
    * @return future for reindexing the change; returns true if the change was stale.
    */
-  public ListenableFuture<Boolean> reindexIfStale(Project.NameKey project, Change.Id id) {
+  public ListenableFuture<Boolean> asyncReindexIfStale(Project.NameKey project, Change.Id id) {
     ReindexIfStaleTask task = new ReindexIfStaleTask(project, id);
     if (queuedReindexIfStaleTasks.add(task)) {
       return submit(task, batchExecutor);
@@ -358,6 +386,41 @@
     return Futures.immediateFuture(false);
   }
 
+  /**
+   * Synchronously check if a change is stale, and reindex if it is.
+   *
+   * @param cd the change data to be checked for staleness.
+   * @return true if the change was stale, false if it was up-to-date
+   */
+  public boolean reindexIfStale(ChangeData cd) {
+    return reindexIfStale(cd.project(), cd.getId());
+  }
+
+  /**
+   * Synchronously check if a change is stale, and reindex if it is.
+   *
+   * @param project the project to which the change belongs.
+   * @param id ID of the change to index.
+   * @return true if the change was stale, false if it was up-to-date
+   */
+  public boolean reindexIfStale(Project.NameKey project, Change.Id id) {
+    try {
+      StalenessCheckResult stalenessCheckResult = stalenessChecker.check(id);
+      if (stalenessCheckResult.isStale()) {
+        logger.atInfo().log("Reindexing stale document %s", stalenessCheckResult);
+        indexImpl(changeDataFactory.create(project, id));
+        return true;
+      }
+    } catch (Exception e) {
+      if (!isCausedByRepositoryNotFoundException(e)) {
+        throw e;
+      }
+      logger.atFine().log(
+          "Change %s belongs to deleted project %s, aborting reindexing the change.", id, project);
+    }
+    return false;
+  }
+
   private void autoReindexIfStale(ChangeData cd) {
     autoReindexIfStale(cd.project(), cd.getId());
   }
@@ -366,7 +429,7 @@
     if (autoReindexIfStale) {
       // Don't retry indefinitely; if this fails the change will be stale.
       @SuppressWarnings("unused")
-      Future<?> possiblyIgnoredError = reindexIfStale(project, id);
+      Future<?> possiblyIgnoredError = asyncReindexIfStale(project, id);
     }
   }
 
@@ -546,22 +609,7 @@
     @Override
     public Boolean callImpl() throws Exception {
       remove();
-      try {
-        StalenessCheckResult stalenessCheckResult = stalenessChecker.check(id);
-        if (stalenessCheckResult.isStale()) {
-          logger.atInfo().log("Reindexing stale document %s", stalenessCheckResult);
-          indexImpl(changeDataFactory.create(project, id));
-          return true;
-        }
-      } catch (Exception e) {
-        if (!isCausedByRepositoryNotFoundException(e)) {
-          throw e;
-        }
-        logger.atFine().log(
-            "Change %s belongs to deleted project %s, aborting reindexing the change.",
-            id.get(), project.get());
-      }
-      return false;
+      return reindexIfStale(project, id);
     }
 
     @Override

diff --git a/java/com/google/gerrit/server/index/change/IndexedChangeQuery.java b/java/com/google/gerrit/server/index/change/IndexedChangeQuery.java
index 00642a9..f7ff13c 100644
--- a/java/com/google/gerrit/server/index/change/IndexedChangeQuery.java
+++ b/java/com/google/gerrit/server/index/change/IndexedChangeQuery.java

@@ -21,6 +21,7 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.index.IndexConfig;
@@ -51,6 +52,10 @@
  */
 public class IndexedChangeQuery extends IndexedQuery<Change.Id, ChangeData>
     implements ChangeDataSource, Matchable<ChangeData> {
+  public static QueryOptions oneResult() {
+    IndexConfig config = IndexConfig.createDefault();
+    return createOptions(config, 0, 1, config.pageSizeMultiplier(), 1, ImmutableSet.of());
+  }
 
   public static QueryOptions createOptions(
       IndexConfig config, int start, int limit, Set<String> fields) {

diff --git a/java/com/google/gerrit/server/index/change/StalenessChecker.java b/java/com/google/gerrit/server/index/change/StalenessChecker.java
index eb4af01..83f6189 100644
--- a/java/com/google/gerrit/server/index/change/StalenessChecker.java
+++ b/java/com/google/gerrit/server/index/change/StalenessChecker.java

@@ -27,6 +27,7 @@
 import com.google.common.collect.SetMultimap;
 import com.google.common.collect.Sets;
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.UsedAt;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Project;
@@ -36,8 +37,8 @@
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.index.StalenessCheckResult;
 import com.google.gerrit.server.query.change.ChangeData;
-import com.google.inject.Inject;
-import com.google.inject.Singleton;
+import com.google.inject.assistedinject.Assisted;
+import com.google.inject.assistedinject.AssistedInject;
 import java.io.IOException;
 import java.util.List;
 import java.util.Optional;
@@ -50,34 +51,58 @@
  * Checker that compares values stored in the change index to metadata in NoteDb to detect index
  * documents that should have been updated (= stale).
  */
-@Singleton
 public class StalenessChecker {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
+  public interface Factory {
+    StalenessChecker create(ChangeIndex index);
+  }
+
   public static final ImmutableSet<String> FIELDS =
       ImmutableSet.of(
           ChangeField.CHANGE_SPEC.getName(),
           ChangeField.REF_STATE_SPEC.getName(),
           ChangeField.REF_STATE_PATTERN_SPEC.getName());
 
-  private final ChangeIndexCollection indexes;
+  @Nullable private final ChangeIndexCollection indexes;
+  @Nullable private final ChangeIndex index;
   private final GitRepositoryManager repoManager;
   private final IndexConfig indexConfig;
 
-  @Inject
-  StalenessChecker(
+  public StalenessChecker(
       ChangeIndexCollection indexes, GitRepositoryManager repoManager, IndexConfig indexConfig) {
     this.indexes = indexes;
+    this.index = null;
     this.repoManager = repoManager;
     this.indexConfig = indexConfig;
   }
 
+  @AssistedInject
+  StalenessChecker(
+      GitRepositoryManager repoManager, IndexConfig indexConfig, @Assisted ChangeIndex index) {
+    this.indexes = null;
+    this.repoManager = repoManager;
+    this.indexConfig = indexConfig;
+    this.index = index;
+  }
+
   /**
    * Returns a {@link StalenessCheckResult} with structured information about staleness of the
    * provided {@link com.google.gerrit.entities.Change.Id}.
    */
   public StalenessCheckResult check(Change.Id id) {
-    ChangeIndex i = indexes.getSearchIndex();
+    if (index != null) {
+      return check(id, index);
+    }
+    return check(id, indexes.getSearchIndex());
+  }
+
+  /**
+   * Returns a {@link StalenessCheckResult} with structured information about staleness of the
+   * provided {@link com.google.gerrit.entities.Change.Id} in the provided {@link
+   * com.google.gerrit.server.index.change.ChangeIndex}.
+   */
+  private StalenessCheckResult check(Change.Id id, ChangeIndex i) {
     if (i == null) {
       return StalenessCheckResult
           .notStale(); // No index; caller couldn't do anything if it is stale.

diff --git a/java/com/google/gerrit/server/restapi/config/ConfigRestApiModule.java b/java/com/google/gerrit/server/restapi/config/ConfigRestApiModule.java
index 77caab4..fdb7d0e 100644
--- a/java/com/google/gerrit/server/restapi/config/ConfigRestApiModule.java
+++ b/java/com/google/gerrit/server/restapi/config/ConfigRestApiModule.java

@@ -16,6 +16,7 @@
 
 import static com.google.gerrit.server.config.ConfigResource.CONFIG_KIND;
 import static com.google.gerrit.server.config.IndexResource.INDEX_KIND;
+import static com.google.gerrit.server.config.IndexVersionResource.INDEX_VERSION_KIND;
 import static com.google.gerrit.server.config.TaskResource.TASK_KIND;
 
 import com.google.gerrit.extensions.registration.DynamicMap;
@@ -31,6 +32,7 @@
     DynamicMap.mapOf(binder(), TASK_KIND);
     DynamicMap.mapOf(binder(), TopMenuResource.TOP_MENU_KIND);
     DynamicMap.mapOf(binder(), INDEX_KIND);
+    DynamicMap.mapOf(binder(), INDEX_VERSION_KIND);
 
     child(CONFIG_KIND, "capabilities").to(CapabilitiesCollection.class);
     post(CONFIG_KIND, "check.consistency").to(CheckConsistency.class);
@@ -44,6 +46,7 @@
     get(CONFIG_KIND, "preferences.edit").to(GetEditPreferences.class);
     put(CONFIG_KIND, "preferences.edit").to(SetEditPreferences.class);
     post(CONFIG_KIND, "reload").to(ReloadConfig.class);
+    post(CONFIG_KIND, "snapshot.indexes").to(SnapshotIndexes.class);
 
     child(CONFIG_KIND, "tasks").to(TasksCollection.class);
     delete(TASK_KIND).to(DeleteTask.class);
@@ -53,7 +56,13 @@
     get(CONFIG_KIND, "version").to(GetVersion.class);
 
     child(CONFIG_KIND, "indexes").to(IndexCollection.class);
-    put(INDEX_KIND, "snapshot").to(SnapshotIndex.class);
+    post(INDEX_KIND, "snapshot").to(SnapshotIndex.class);
+    get(INDEX_KIND).to(GetIndex.class);
+
+    child(INDEX_KIND, "versions").to(IndexVersionsCollection.class);
+    get(INDEX_VERSION_KIND).to(GetIndexVersion.class);
+    post(INDEX_VERSION_KIND, "snapshot").to(SnapshotIndexVersion.class);
+    post(INDEX_VERSION_KIND, "reindex").to(ReindexIndexVersion.class);
 
     // The caches and summary REST endpoints are bound via RestCacheAdminModule.
   }

diff --git a/java/com/google/gerrit/server/restapi/config/GetIndex.java b/java/com/google/gerrit/server/restapi/config/GetIndex.java
new file mode 100644
index 0000000..c96c66e
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/GetIndex.java

@@ -0,0 +1,31 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.config.IndexResource;
+
+public class GetIndex implements RestReadView<IndexResource> {
+
+  @Override
+  public Response<IndexInfo> apply(IndexResource rsrc)
+      throws AuthException, BadRequestException, ResourceConflictException, Exception {
+    return Response.ok(IndexInfo.fromIndexDefinition(rsrc.getIndexDefinition()));
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/GetIndexVersion.java b/java/com/google/gerrit/server/restapi/config/GetIndexVersion.java
new file mode 100644
index 0000000..1955511
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/GetIndexVersion.java

@@ -0,0 +1,35 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.index.IndexCollection;
+import com.google.gerrit.server.config.IndexVersionResource;
+import com.google.gerrit.server.restapi.config.IndexInfo.IndexVersionInfo;
+
+public class GetIndexVersion implements RestReadView<IndexVersionResource> {
+
+  @Override
+  public Response<IndexVersionInfo> apply(IndexVersionResource rsrc)
+      throws ResourceNotFoundException {
+    IndexCollection<?, ?, ?> indexCollection = rsrc.getIndexDefinition().getIndexCollection();
+    int version = rsrc.getIndex().getSchema().getVersion();
+    boolean isSearch = indexCollection.getSearchIndex().getSchema().getVersion() == version;
+    boolean isWrite = indexCollection.getWriteIndex(version) != null;
+    return Response.ok(IndexInfo.IndexVersionInfo.create(isWrite, isSearch));
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/IndexCollection.java b/java/com/google/gerrit/server/restapi/config/IndexCollection.java
index c5d295d..99a5718 100644
--- a/java/com/google/gerrit/server/restapi/config/IndexCollection.java
+++ b/java/com/google/gerrit/server/restapi/config/IndexCollection.java

@@ -16,8 +16,6 @@
 
 import static com.google.gerrit.common.data.GlobalCapability.MAINTAIN_SERVER;
 
-import com.google.common.base.Splitter;
-import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.annotations.RequiresCapability;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.restapi.ChildCollection;
@@ -32,8 +30,6 @@
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import java.util.Collection;
-import java.util.List;
-import java.util.Locale;
 
 @RequiresCapability(MAINTAIN_SERVER)
 @Singleton
@@ -54,25 +50,10 @@
 
   @Override
   public IndexResource parse(ConfigResource parent, IdString id) throws ResourceNotFoundException {
-    if (id.toString().toLowerCase(Locale.US).equals("all")) {
-      ImmutableList.Builder<com.google.gerrit.index.IndexCollection<?, ?, ?>> allIndexes =
-          ImmutableList.builder();
-      for (IndexDefinition<?, ?, ?> def : defs) {
-        allIndexes.add(def.getIndexCollection());
-      }
-      return new IndexResource(allIndexes.build());
-    }
-
-    List<String> segments = Splitter.on('~').splitToList(id.toString());
-    if (segments.size() < 1 || 2 < segments.size()) {
-      throw new ResourceNotFoundException(id);
-    }
-    String indexName = segments.get(0);
-    Integer version = segments.size() == 2 ? Integer.valueOf(segments.get(1)) : null;
-
+    String indexName = id.toString();
     for (IndexDefinition<?, ?, ?> def : defs) {
       if (def.getName().equals(indexName)) {
-        return new IndexResource(def.getIndexCollection(), version);
+        return new IndexResource(def);
       }
     }
     throw new ResourceNotFoundException("Unknown index requested: " + indexName);

diff --git a/java/com/google/gerrit/server/restapi/config/IndexInfo.java b/java/com/google/gerrit/server/restapi/config/IndexInfo.java
index 4a6bd3e53..5d52fe1 100644
--- a/java/com/google/gerrit/server/restapi/config/IndexInfo.java
+++ b/java/com/google/gerrit/server/restapi/config/IndexInfo.java

@@ -19,6 +19,7 @@
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.gerrit.index.Index;
 import com.google.gerrit.index.IndexCollection;
+import com.google.gerrit.index.IndexDefinition;
 
 @AutoValue
 public abstract class IndexInfo {
@@ -41,6 +42,10 @@
     return new AutoValue_IndexInfo(name, versions.build());
   }
 
+  public static IndexInfo fromIndexDefinition(IndexDefinition<?, ?, ?> def) {
+    return fromIndexCollection(def.getName(), def.getIndexCollection());
+  }
+
   public abstract String getName();
 
   public abstract ImmutableMap<Integer, IndexVersionInfo> getVersions();

diff --git a/java/com/google/gerrit/server/restapi/config/IndexVersionsCollection.java b/java/com/google/gerrit/server/restapi/config/IndexVersionsCollection.java
new file mode 100644
index 0000000..44c49f3
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/IndexVersionsCollection.java

@@ -0,0 +1,83 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import static com.google.gerrit.common.data.GlobalCapability.MAINTAIN_SERVER;
+
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.extensions.restapi.ChildCollection;
+import com.google.gerrit.extensions.restapi.IdString;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.extensions.restapi.RestView;
+import com.google.gerrit.index.Index;
+import com.google.gerrit.index.IndexCollection;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.server.config.IndexResource;
+import com.google.gerrit.server.config.IndexVersionResource;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+
+@RequiresCapability(MAINTAIN_SERVER)
+@Singleton
+public class IndexVersionsCollection
+    implements ChildCollection<IndexResource, IndexVersionResource> {
+
+  private final DynamicMap<RestView<IndexVersionResource>> views;
+  private final Provider<ListIndexVersions> list;
+
+  @Inject
+  IndexVersionsCollection(
+      DynamicMap<RestView<IndexVersionResource>> views, Provider<ListIndexVersions> list) {
+    this.views = views;
+    this.list = list;
+  }
+
+  @Override
+  public RestView<IndexResource> list() throws RestApiException {
+    return list.get();
+  }
+
+  @Override
+  public IndexVersionResource parse(IndexResource parent, IdString id)
+      throws ResourceNotFoundException, Exception {
+    try {
+      int version = Integer.parseInt(id.get());
+      IndexDefinition<?, ?, ?> def = parent.getIndexDefinition();
+      IndexCollection<?, ?, ?> indexCollection = def.getIndexCollection();
+      Index<?, ?> index = indexCollection.getWriteIndex(version);
+      if (index == null) {
+        Index<?, ?> searchIndex = indexCollection.getSearchIndex();
+        if (searchIndex.getSchema().getVersion() == version) {
+          index = searchIndex;
+        }
+      }
+      if (index != null) {
+        return new IndexVersionResource(def, index);
+      }
+    } catch (NumberFormatException e) {
+      throw new ResourceNotFoundException("'" + id.get() + "' is not a number", e);
+    }
+
+    throw new ResourceNotFoundException();
+  }
+
+  @Override
+  public DynamicMap<RestView<IndexVersionResource>> views() {
+    return views;
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/ListIndexVersions.java b/java/com/google/gerrit/server/restapi/config/ListIndexVersions.java
new file mode 100644
index 0000000..91bdae0
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/ListIndexVersions.java

@@ -0,0 +1,37 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import static com.google.gerrit.common.data.GlobalCapability.MAINTAIN_SERVER;
+
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.config.IndexResource;
+import java.util.Map;
+
+@RequiresCapability(MAINTAIN_SERVER)
+public class ListIndexVersions implements RestReadView<IndexResource> {
+
+  @Override
+  public Response<Map<Integer, IndexInfo.IndexVersionInfo>> apply(IndexResource rsrc)
+      throws AuthException, BadRequestException, ResourceConflictException, Exception {
+    IndexInfo info = IndexInfo.fromIndexDefinition(rsrc.getIndexDefinition());
+    return Response.ok(info.getVersions());
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/ListIndexes.java b/java/com/google/gerrit/server/restapi/config/ListIndexes.java
index 9710000..2e6664b 100644
--- a/java/com/google/gerrit/server/restapi/config/ListIndexes.java
+++ b/java/com/google/gerrit/server/restapi/config/ListIndexes.java

@@ -16,6 +16,7 @@
 
 import static com.google.gerrit.common.data.GlobalCapability.MAINTAIN_SERVER;
 
+import com.google.common.collect.ImmutableList;
 import com.google.gerrit.extensions.annotations.RequiresCapability;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestReadView;
@@ -23,8 +24,6 @@
 import com.google.gerrit.server.config.ConfigResource;
 import com.google.inject.Inject;
 import java.util.Collection;
-import java.util.Map;
-import java.util.TreeMap;
 
 @RequiresCapability(MAINTAIN_SERVER)
 public class ListIndexes implements RestReadView<ConfigResource> {
@@ -35,13 +34,12 @@
     this.defs = defs;
   }
 
-  private Map<String, IndexInfo> getIndexInfos() {
-    Map<String, IndexInfo> indexInfos = new TreeMap<>();
+  private ImmutableList<IndexInfo> getIndexInfos() {
+    ImmutableList.Builder<IndexInfo> indexInfos = ImmutableList.builder();
     for (IndexDefinition<?, ?, ?> def : defs) {
-      String name = def.getName();
-      indexInfos.put(name, IndexInfo.fromIndexCollection(name, def.getIndexCollection()));
+      indexInfos.add(IndexInfo.fromIndexDefinition(def));
     }
-    return indexInfos;
+    return indexInfos.build();
   }
 
   @Override

diff --git a/java/com/google/gerrit/server/restapi/config/ReindexIndexVersion.java b/java/com/google/gerrit/server/restapi/config/ReindexIndexVersion.java
new file mode 100644
index 0000000..d923155
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/ReindexIndexVersion.java

@@ -0,0 +1,48 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.server.config.IndexVersionResource;
+import com.google.gerrit.server.index.IndexVersionReindexer;
+import com.google.gerrit.server.restapi.config.ReindexIndexVersion.Input;
+import com.google.inject.Inject;
+
+public class ReindexIndexVersion implements RestModifyView<IndexVersionResource, Input> {
+  public static class Input {
+    boolean reuse;
+  }
+
+  private final IndexVersionReindexer indexVersionReindexer;
+
+  @Inject
+  ReindexIndexVersion(IndexVersionReindexer indexVersionReindexer) {
+    this.indexVersionReindexer = indexVersionReindexer;
+  }
+
+  @Override
+  public Response<?> apply(IndexVersionResource rsrc, Input input)
+      throws ResourceNotFoundException {
+    IndexDefinition<?, ?, ?> def = rsrc.getIndexDefinition();
+    int version = rsrc.getIndex().getSchema().getVersion();
+    @SuppressWarnings("unused")
+    var unused = indexVersionReindexer.reindex(def, version, input.reuse);
+    return Response.accepted(
+        String.format("Index %s version %d submitted for reindexing", def.getName(), version));
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/SnapshotIndex.java b/java/com/google/gerrit/server/restapi/config/SnapshotIndex.java
index 72af97f..c50367f 100644
--- a/java/com/google/gerrit/server/restapi/config/SnapshotIndex.java
+++ b/java/com/google/gerrit/server/restapi/config/SnapshotIndex.java

@@ -21,6 +21,7 @@
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestModifyView;
 import com.google.gerrit.index.Index;
+import com.google.gerrit.index.IndexDefinition;
 import com.google.gerrit.server.config.IndexResource;
 import com.google.gerrit.server.restapi.config.SnapshotIndex.Input;
 import com.google.inject.Singleton;
@@ -29,7 +30,6 @@
 import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
-import java.util.Collection;
 
 @RequiresCapability(MAINTAIN_SERVER)
 @Singleton
@@ -38,12 +38,12 @@
 
   @Override
   public Response<?> apply(IndexResource rsrc, Input input) throws IOException {
-    Collection<Index<?, ?>> indexes = rsrc.getIndexes();
     String id = input.id;
     if (id == null) {
       id = LocalDateTime.now(ZoneId.systemDefault()).format(formatter);
     }
-    for (Index<?, ?> index : indexes) {
+    IndexDefinition<?, ?, ?> def = rsrc.getIndexDefinition();
+    for (Index<?, ?> index : def.getIndexCollection().getWriteIndexes()) {
       try {
         @SuppressWarnings("unused")
         var unused = index.snapshot(id);

diff --git a/java/com/google/gerrit/server/restapi/config/SnapshotIndexVersion.java b/java/com/google/gerrit/server/restapi/config/SnapshotIndexVersion.java
new file mode 100644
index 0000000..9f66ab3
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/SnapshotIndexVersion.java

@@ -0,0 +1,54 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import static com.google.gerrit.common.data.GlobalCapability.MAINTAIN_SERVER;
+
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.index.Index;
+import com.google.gerrit.server.config.IndexVersionResource;
+import com.google.gerrit.server.restapi.config.SnapshotIndexVersion.Input;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+
+@RequiresCapability(MAINTAIN_SERVER)
+@Singleton
+public class SnapshotIndexVersion implements RestModifyView<IndexVersionResource, Input> {
+  private final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss");
+
+  @Override
+  public Response<?> apply(IndexVersionResource rsrc, Input input)
+      throws IOException, ResourceNotFoundException {
+    String id = input.id;
+    if (id == null) {
+      id = LocalDateTime.now(ZoneId.systemDefault()).format(formatter);
+    }
+    Index<?, ?> index = rsrc.getIndex();
+    var unused = index.snapshot(id);
+    SnapshotInfo info = new SnapshotInfo();
+    info.id = id;
+    return Response.ok(info);
+  }
+
+  public static class Input {
+    String id;
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/config/SnapshotIndexes.java b/java/com/google/gerrit/server/restapi/config/SnapshotIndexes.java
new file mode 100644
index 0000000..6a2c5f8
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/config/SnapshotIndexes.java

@@ -0,0 +1,72 @@
+// Copyright (C) 2024 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.restapi.config;
+
+import static javax.servlet.http.HttpServletResponse.SC_CONFLICT;
+
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.index.Index;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.server.config.ConfigResource;
+import com.google.gerrit.server.restapi.config.SnapshotIndexes.Input;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.nio.file.FileAlreadyExistsException;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.Collection;
+
+@RequiresCapability(GlobalCapability.MAINTAIN_SERVER)
+@Singleton
+public class SnapshotIndexes implements RestModifyView<ConfigResource, Input> {
+  private final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss");
+
+  public static class Input {
+    String id;
+  }
+
+  private final Collection<IndexDefinition<?, ?, ?>> defs;
+
+  @Inject
+  SnapshotIndexes(Collection<IndexDefinition<?, ?, ?>> defs) {
+    this.defs = defs;
+  }
+
+  @Override
+  public Response<?> apply(ConfigResource resource, Input input) throws IOException {
+    String id = input.id;
+    if (id == null) {
+      id = LocalDateTime.now(ZoneId.systemDefault()).format(formatter);
+    }
+    for (IndexDefinition<?, ?, ?> def : defs) {
+      for (Index<?, ?> index : def.getIndexCollection().getWriteIndexes()) {
+        try {
+          @SuppressWarnings("unused")
+          var unused = index.snapshot(id);
+        } catch (FileAlreadyExistsException e) {
+          return Response.withStatusCode(SC_CONFLICT, "Snapshot with same ID already exists.");
+        }
+      }
+    }
+    SnapshotInfo info = new SnapshotInfo();
+    info.id = id;
+    return Response.ok(info);
+  }
+}

diff --git a/java/com/google/gerrit/server/restapi/project/IndexChanges.java b/java/com/google/gerrit/server/restapi/project/IndexChanges.java
index 6ad0005..532bd24 100644
--- a/java/com/google/gerrit/server/restapi/project/IndexChanges.java
+++ b/java/com/google/gerrit/server/restapi/project/IndexChanges.java

@@ -32,7 +32,6 @@
 import com.google.gerrit.server.index.change.ChangeIndexer;
 import com.google.gerrit.server.project.ProjectResource;
 import com.google.inject.Inject;
-import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import java.util.concurrent.Future;
 import org.eclipse.jgit.util.io.NullOutputStream;
@@ -42,18 +41,18 @@
 public class IndexChanges implements RestModifyView<ProjectResource, Input> {
 
   private final MultiProgressMonitor.Factory multiProgressMonitorFactory;
-  private final Provider<AllChangesIndexer> allChangesIndexerProvider;
+  private final AllChangesIndexer.Factory allChangesIndexerFactory;
   private final ChangeIndexer indexer;
   private final ListeningExecutorService executor;
 
   @Inject
   IndexChanges(
       MultiProgressMonitor.Factory multiProgressMonitorFactory,
-      Provider<AllChangesIndexer> allChangesIndexerProvider,
+      AllChangesIndexer.Factory allChangesIndexerFactory,
       ChangeIndexer indexer,
       @IndexExecutor(BATCH) ListeningExecutorService executor) {
     this.multiProgressMonitorFactory = multiProgressMonitorFactory;
-    this.allChangesIndexerProvider = allChangesIndexerProvider;
+    this.allChangesIndexerFactory = allChangesIndexerFactory;
     this.indexer = indexer;
     this.executor = executor;
   }
@@ -65,7 +64,7 @@
         multiProgressMonitorFactory
             .create(ByteStreams.nullOutputStream(), TaskKind.INDEXING, "Reindexing project")
             .beginSubTask("", MultiProgressMonitor.UNKNOWN);
-    AllChangesIndexer allChangesIndexer = allChangesIndexerProvider.get();
+    AllChangesIndexer allChangesIndexer = allChangesIndexerFactory.create();
     allChangesIndexer.setVerboseOut(NullOutputStream.INSTANCE);
     // The REST call is just a trigger for async reindexing, so it is safe to ignore the future's
     // return value.

diff --git a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
index c5059c3..66c4078 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java

@@ -30,6 +30,7 @@
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.api.GerritApi;
+import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.common.ChangeInput;
 import com.google.gerrit.index.IndexDefinition;
 import com.google.gerrit.index.Schema;
@@ -67,9 +68,45 @@
     Files.createDirectory(sitePaths.index_dir);
     assertServerStartupFails();
 
-    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace");
+    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace", "--verbose");
+    assertReady(ChangeSchemaDefinitions.INSTANCE.getLatest().getVersion());
+    assertIndexQueries();
+  }
+
+  @Test
+  public void reindexWithSkipExistingDocumentsEnabled() throws Exception {
+    updateConfig(config -> config.setBoolean("index", null, "reuseExistingDocuments", true));
+    setUpChange();
+
+    MoreFiles.deleteRecursively(sitePaths.index_dir, RecursiveDeleteOption.ALLOW_INSECURE);
+    Files.createDirectory(sitePaths.index_dir);
+    assertServerStartupFails();
+
+    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace", "--verbose");
     assertReady(ChangeSchemaDefinitions.INSTANCE.getLatest().getVersion());
 
+    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace", "--verbose");
+    assertIndexQueries();
+
+    Files.copy(sitePaths.index_dir, sitePaths.resolve("index-backup"));
+    try (ServerContext ctx = startServer()) {
+      GerritApi gApi = ctx.getInjector().getInstance(GerritApi.class);
+      gApi.changes().id(changeId).revision(1).review(ReviewInput.approve());
+      // Query change index
+      assertThat(gApi.changes().query("label:Code-Review+2").get().stream().map(c -> c.changeId))
+          .containsExactly(changeId);
+    }
+    MoreFiles.deleteRecursively(sitePaths.index_dir, RecursiveDeleteOption.ALLOW_INSECURE);
+    Files.copy(sitePaths.resolve("index-backup"), sitePaths.index_dir);
+    runGerrit("reindex", "-d", sitePaths.site_path.toString(), "--show-stack-trace", "--verbose");
+    try (ServerContext ctx = startServer()) {
+      GerritApi gApi = ctx.getInjector().getInstance(GerritApi.class);
+      assertThat(gApi.changes().query("label:Code-Review+2").get().stream().map(c -> c.changeId))
+          .containsExactly(changeId);
+    }
+  }
+
+  private void assertIndexQueries() throws Exception {
     try (ServerContext ctx = startServer()) {
       GerritApi gApi = ctx.getInjector().getInstance(GerritApi.class);
       // Query change index

diff --git a/javatests/com/google/gerrit/acceptance/rest/config/IndexSnapshotsIT.java b/javatests/com/google/gerrit/acceptance/rest/config/IndexSnapshotsIT.java
index a88ee3e..904de9a 100644
--- a/javatests/com/google/gerrit/acceptance/rest/config/IndexSnapshotsIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/config/IndexSnapshotsIT.java

@@ -16,21 +16,20 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.common.collect.ImmutableList;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.UseLocalDisk;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.index.Index;
-import com.google.gerrit.index.IndexCollection;
-import com.google.gerrit.index.IndexDefinition;
 import com.google.gerrit.index.IndexType;
-import com.google.gerrit.index.project.ProjectIndexCollection;
+import com.google.gerrit.server.config.ConfigResource;
 import com.google.gerrit.server.config.IndexResource;
 import com.google.gerrit.server.config.SitePaths;
-import com.google.gerrit.server.index.account.AccountIndexCollection;
-import com.google.gerrit.server.index.change.ChangeIndexCollection;
-import com.google.gerrit.server.index.group.GroupIndexCollection;
+import com.google.gerrit.server.index.account.AccountIndexDefinition;
+import com.google.gerrit.server.index.change.ChangeIndexDefinition;
+import com.google.gerrit.server.index.group.GroupIndexDefinition;
+import com.google.gerrit.server.index.project.ProjectIndexDefinition;
 import com.google.gerrit.server.restapi.config.SnapshotIndex;
+import com.google.gerrit.server.restapi.config.SnapshotIndexes;
 import com.google.gerrit.server.restapi.config.SnapshotInfo;
 import com.google.gerrit.testing.SystemPropertiesTestRule;
 import com.google.inject.Inject;
@@ -57,22 +56,25 @@
       new SystemPropertiesTestRule(IndexType.SYS_PROP, "lucene");
 
   @Inject private SnapshotIndex snapshotIndex;
-  @Inject private AccountIndexCollection accountIndexes;
-  @Inject private ChangeIndexCollection changeIndexes;
-  @Inject private GroupIndexCollection groupIndexes;
-  @Inject private ProjectIndexCollection projectIndexes;
+  @Inject private SnapshotIndexes snapshotIndexes;
+  @Inject private AccountIndexDefinition accountIndexDefinition;
+  @Inject private ChangeIndexDefinition changeIndexDefinition;
+  @Inject private GroupIndexDefinition groupIndexDefinition;
+  @Inject private ProjectIndexDefinition projectIndexDefinition;
 
   @Inject private SitePaths sitePaths;
-  @Inject private Collection<IndexDefinition<?, ?, ?>> defs;
+
+  @Test
+  @UseLocalDisk
+  public void createAccountsIndexSnapshot() throws Exception {
+    Query query = new TermQuery(new Term("is", "active"));
+    createAndVerifySnapshot(new IndexResource(accountIndexDefinition), "accounts", query);
+  }
 
   @Test
   @UseLocalDisk
   public void createFullSnapshot() throws Exception {
-    ImmutableList.Builder<IndexCollection<?, ?, ?>> indexCollections = ImmutableList.builder();
-    for (IndexDefinition<?, ?, ?> def : defs) {
-      indexCollections.add(def.getIndexCollection());
-    }
-    File snapshot = createSnapshot(new IndexResource(indexCollections.build()));
+    File snapshot = createSnapshotOfAllIndexes();
     File[] members = snapshot.listFiles();
     for (File member : members) {
       assertThat(member.isDirectory()).isTrue();
@@ -82,30 +84,23 @@
 
   @Test
   @UseLocalDisk
-  public void createAccountsIndexSnapshot() throws Exception {
-    Query query = new TermQuery(new Term("is", "active"));
-    createAndVerifySnapshot(new IndexResource(accountIndexes, null), "accounts", query);
-  }
-
-  @Test
-  @UseLocalDisk
   public void createChangesIndexSnapshot() throws Exception {
     Query query = new TermQuery(new Term("status", "open"));
-    createAndVerifySnapshot(new IndexResource(changeIndexes, null), "changes", query);
+    createAndVerifySnapshot(new IndexResource(changeIndexDefinition), "changes", query);
   }
 
   @Test
   @UseLocalDisk
   public void createGroupsIndexSnapshot() throws Exception {
     Query query = new TermQuery(new Term("is", "active"));
-    createAndVerifySnapshot(new IndexResource(groupIndexes, null), "groups", query);
+    createAndVerifySnapshot(new IndexResource(groupIndexDefinition), "groups", query);
   }
 
   @Test
   @UseLocalDisk
   public void createProjectsIndexSnapshot() throws Exception {
     Query query = new TermQuery(new Term("name", "foo"));
-    createAndVerifySnapshot(new IndexResource(projectIndexes, null), "projects", query);
+    createAndVerifySnapshot(new IndexResource(projectIndexDefinition), "projects", query);
   }
 
   private File createAndVerifySnapshot(IndexResource rsrc, String prefix, Query query)
@@ -113,8 +108,10 @@
     File snapshot = createSnapshot(rsrc);
 
     File[] subdirs = snapshot.listFiles();
-    assertThat(subdirs).hasLength(rsrc.getIndexes().size());
-    for (Index<?, ?> i : rsrc.getIndexes()) {
+    Collection<? extends Index<?, ?>> indexes =
+        rsrc.getIndexDefinition().getIndexCollection().getWriteIndexes();
+    assertThat(subdirs).hasLength(indexes.size());
+    for (Index<?, ?> i : indexes) {
       String indexDirName = String.format("%s_%04d", prefix, i.getSchema().getVersion());
       File[] result = snapshot.listFiles((d, n) -> n.equals(indexDirName));
       assertThat(result).hasLength(1);
@@ -126,6 +123,15 @@
 
   private File createSnapshot(IndexResource rsrc) throws IOException {
     Response<?> rsp = snapshotIndex.apply(rsrc, new SnapshotIndex.Input());
+    return verifySnapshot(rsp);
+  }
+
+  private File createSnapshotOfAllIndexes() throws IOException {
+    Response<?> rsp = snapshotIndexes.apply(new ConfigResource(), new SnapshotIndexes.Input());
+    return verifySnapshot(rsp);
+  }
+
+  private File verifySnapshot(Response<?> rsp) {
     assertThat(rsp.value()).isInstanceOf(SnapshotInfo.class);
     SnapshotInfo snapshotInfo = (SnapshotInfo) rsp.value();
     Path snapshotDir = sitePaths.index_dir.resolve("snapshots").resolve(snapshotInfo.id);

diff --git a/javatests/com/google/gerrit/acceptance/server/index/change/BUILD b/javatests/com/google/gerrit/acceptance/server/index/change/BUILD
new file mode 100644
index 0000000..3be5249
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/server/index/change/BUILD

@@ -0,0 +1,7 @@
+load("//javatests/com/google/gerrit/acceptance:tests.bzl", "acceptance_tests")
+
+acceptance_tests(
+    srcs = glob(["*IT.java"]),
+    group = "server_index",
+    labels = ["server"],
+)

diff --git a/javatests/com/google/gerrit/acceptance/server/index/change/LuceneChangeIndexerIT.java b/javatests/com/google/gerrit/acceptance/server/index/change/LuceneChangeIndexerIT.java
new file mode 100644
index 0000000..b8af367
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/server/index/change/LuceneChangeIndexerIT.java

@@ -0,0 +1,137 @@
+// Copyright (C) 2024 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.server.index.change;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableSetMultimap;
+import com.google.common.collect.LinkedListMultimap;
+import com.google.common.collect.ListMultimap;
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ChangeIndexedCounter;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
+import com.google.gerrit.acceptance.PushOneCommit;
+import com.google.gerrit.acceptance.config.GerritConfig;
+import com.google.gerrit.entities.Project.NameKey;
+import com.google.gerrit.index.IndexDefinition;
+import com.google.gerrit.index.RefState;
+import com.google.gerrit.index.SiteIndexer.Result;
+import com.google.gerrit.server.index.change.AllChangesIndexer;
+import com.google.gerrit.server.index.change.ChangeIndex;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.testing.ConfigSuite;
+import com.google.inject.Inject;
+import java.util.Collection;
+import java.util.Set;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Before;
+import org.junit.Test;
+
+public class LuceneChangeIndexerIT extends AbstractDaemonTest {
+  @ConfigSuite.Default
+  public static Config defaultConfig() {
+    Config cfg = new Config();
+    cfg.setBoolean("index", null, "autoReindexIfStale", false);
+    cfg.setString("index", null, "type", "lucene");
+    return cfg;
+  }
+
+  @Inject private ExtensionRegistry extensionRegistry;
+
+  @Inject private Collection<IndexDefinition<?, ?, ?>> indexDefs;
+  private AllChangesIndexer allChangesIndexer;
+  private ChangeIndex index;
+
+  @Before
+  public void setup() {
+    IndexDefinition<?, ?, ?> changeIndex =
+        indexDefs.stream().filter(i -> i.getName().equals("changes")).findFirst().get();
+    allChangesIndexer = (AllChangesIndexer) changeIndex.getSiteIndexer();
+    index = (ChangeIndex) changeIndex.getIndexCollection().getWriteIndexes().iterator().next();
+  }
+
+  @Test
+  @GerritConfig(name = "index.reuseExistingDocuments", value = "false")
+  public void testReindexWithoutReuse() throws Exception {
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      createChange();
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(1);
+      changeIndexedCounter.clear();
+      reindexChanges();
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(1);
+
+      createIndexWithMissingChangeAndReindex(changeIndexedCounter);
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(2);
+
+      createIndexWithStaleChangeAndReindex(changeIndexedCounter);
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(3);
+    }
+  }
+
+  @Test
+  @GerritConfig(name = "index.reuseExistingDocuments", value = "true")
+  public void testReindexWithReuse() throws Exception {
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      createChange();
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(1);
+      changeIndexedCounter.clear();
+      reindexChanges();
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(0);
+
+      createIndexWithMissingChangeAndReindex(changeIndexedCounter);
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(1);
+
+      createIndexWithStaleChangeAndReindex(changeIndexedCounter);
+      assertThat(changeIndexedCounter.getTotalCount()).isEqualTo(1);
+    }
+  }
+
+  private void createIndexWithMissingChangeAndReindex(ChangeIndexedCounter changeIndexedCounter)
+      throws Exception {
+    PushOneCommit.Result res = createChange();
+    index.delete(res.getChange().getId());
+    changeIndexedCounter.clear();
+    reindexChanges();
+  }
+
+  private void createIndexWithStaleChangeAndReindex(ChangeIndexedCounter changeIndexedCounter)
+      throws Exception {
+    PushOneCommit.Result res = createChange();
+    ChangeData wrongChangeData = res.getChange();
+    ListMultimap<NameKey, RefState> refStates =
+        LinkedListMultimap.create(wrongChangeData.getRefStates());
+    refStates.replaceValues(
+        project,
+        Set.of(
+            RefState.create(
+                "refs/changes/abcd",
+                ObjectId.fromString("deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"))));
+    wrongChangeData.setRefStates(ImmutableSetMultimap.copyOf(refStates));
+    index.replace(wrongChangeData);
+    changeIndexedCounter.clear();
+    reindexChanges();
+  }
+
+  private void reindexChanges() throws Exception {
+    Result res = allChangesIndexer.indexAll(index);
+    assertThat(res.success()).isTrue();
+  }
+}

diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index 6258b18..7a7cff5 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java

@@ -3576,7 +3576,7 @@
     getChangeApi(change).addReviewer(anotherUser.toString());
 
     assertQuery("reviewer:self", change);
-    assertThat(indexer.reindexIfStale(project, change.getId()).get()).isFalse();
+    assertThat(indexer.reindexIfStale(project, change.getId())).isFalse();
 
     // Remove reviewer behind index's back.
     ChangeUpdate update = newUpdate(change);
@@ -3585,7 +3585,7 @@
 
     // Index is stale.
     assertQuery("reviewer:self", change);
-    assertThat(indexer.reindexIfStale(project, change.getId()).get()).isTrue();
+    assertThat(indexer.reindexIfStale(project, change.getId())).isTrue();
     assertQuery("reviewer:self");
 
     // Index is not stale when a draft comment exists
@@ -3594,7 +3594,7 @@
     in.message = "nit: trailing whitespace";
     in.path = Patch.COMMIT_MSG;
     getChangeApi(change).current().createDraft(in);
-    assertThat(indexer.reindexIfStale(project, change.getId()).get()).isFalse();
+    assertThat(indexer.reindexIfStale(project, change.getId())).isFalse();
   }
 
   @Test