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diff --git a/java/com/google/gerrit/server/Sequences.java b/java/com/google/gerrit/server/Sequences.java
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+++ b/java/com/google/gerrit/server/Sequences.java
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+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.metrics.Description;
+import com.google.gerrit.metrics.Description.Units;
+import com.google.gerrit.metrics.Field;
+import com.google.gerrit.metrics.MetricMaker;
+import com.google.gerrit.metrics.Timer2;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.config.AllProjectsName;
+import com.google.gerrit.server.config.AllUsersName;
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.notedb.RepoSequence;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import java.util.ArrayList;
+import java.util.List;
+import org.eclipse.jgit.lib.Config;
+
+@Singleton
+public class Sequences {
+  public static final String NAME_ACCOUNTS = "accounts";
+  public static final String NAME_GROUPS = "groups";
+  public static final String NAME_CHANGES = "changes";
+
+  public static int getChangeSequenceGap(Config cfg) {
+    return cfg.getInt("noteDb", "changes", "initialSequenceGap", 1000);
+  }
+
+  private enum SequenceType {
+    ACCOUNTS,
+    CHANGES,
+    GROUPS;
+  }
+
+  private final Provider<ReviewDb> db;
+  private final NotesMigration migration;
+  private final RepoSequence accountSeq;
+  private final RepoSequence changeSeq;
+  private final RepoSequence groupSeq;
+  private final Timer2<SequenceType, Boolean> nextIdLatency;
+
+  @Inject
+  public Sequences(
+      @GerritServerConfig Config cfg,
+      Provider<ReviewDb> db,
+      NotesMigration migration,
+      GitRepositoryManager repoManager,
+      GitReferenceUpdated gitRefUpdated,
+      AllProjectsName allProjects,
+      AllUsersName allUsers,
+      MetricMaker metrics) {
+    this.db = db;
+    this.migration = migration;
+
+    int accountBatchSize = cfg.getInt("noteDb", "accounts", "sequenceBatchSize", 1);
+    accountSeq =
+        new RepoSequence(
+            repoManager,
+            gitRefUpdated,
+            allUsers,
+            NAME_ACCOUNTS,
+            () -> ReviewDb.FIRST_ACCOUNT_ID,
+            accountBatchSize);
+
+    int gap = getChangeSequenceGap(cfg);
+    @SuppressWarnings("deprecation")
+    RepoSequence.Seed changeSeed = () -> db.get().nextChangeId() + gap;
+    int changeBatchSize = cfg.getInt("noteDb", "changes", "sequenceBatchSize", 20);
+    changeSeq =
+        new RepoSequence(
+            repoManager, gitRefUpdated, allProjects, NAME_CHANGES, changeSeed, changeBatchSize);
+
+    RepoSequence.Seed groupSeed = () -> nextGroupId(db.get());
+    int groupBatchSize = 1;
+    groupSeq =
+        new RepoSequence(
+            repoManager, gitRefUpdated, allUsers, NAME_GROUPS, groupSeed, groupBatchSize);
+
+    nextIdLatency =
+        metrics.newTimer(
+            "sequence/next_id_latency",
+            new Description("Latency of requesting IDs from repo sequences")
+                .setCumulative()
+                .setUnit(Units.MILLISECONDS),
+            Field.ofEnum(SequenceType.class, "sequence"),
+            Field.ofBoolean("multiple"));
+  }
+
+  public int nextAccountId() throws OrmException {
+    try (Timer2.Context timer = nextIdLatency.start(SequenceType.ACCOUNTS, false)) {
+      return accountSeq.next();
+    }
+  }
+
+  public int nextChangeId() throws OrmException {
+    if (!migration.readChangeSequence()) {
+      return nextChangeId(db.get());
+    }
+    try (Timer2.Context timer = nextIdLatency.start(SequenceType.CHANGES, false)) {
+      return changeSeq.next();
+    }
+  }
+
+  public ImmutableList<Integer> nextChangeIds(int count) throws OrmException {
+    if (migration.readChangeSequence()) {
+      try (Timer2.Context timer = nextIdLatency.start(SequenceType.CHANGES, count > 1)) {
+        return changeSeq.next(count);
+      }
+    }
+
+    if (count == 0) {
+      return ImmutableList.of();
+    }
+    checkArgument(count > 0, "count is negative: %s", count);
+    List<Integer> ids = new ArrayList<>(count);
+    ReviewDb db = this.db.get();
+    for (int i = 0; i < count; i++) {
+      ids.add(nextChangeId(db));
+    }
+    return ImmutableList.copyOf(ids);
+  }
+
+  public int nextGroupId() throws OrmException {
+    try (Timer2.Context timer = nextIdLatency.start(SequenceType.GROUPS, false)) {
+      return groupSeq.next();
+    }
+  }
+
+  @VisibleForTesting
+  public RepoSequence getChangeIdRepoSequence() {
+    return changeSeq;
+  }
+
+  @SuppressWarnings("deprecation")
+  private static int nextChangeId(ReviewDb db) throws OrmException {
+    return db.nextChangeId();
+  }
+
+  @SuppressWarnings("deprecation")
+  static int nextGroupId(ReviewDb db) throws OrmException {
+    return db.nextAccountGroupId();
+  }
+}