1 files changed, 77 insertions, 0 deletions
diff --git a/java/com/google/gerrit/reviewdb/server/ReviewDbUtil.java b/java/com/google/gerrit/reviewdb/server/ReviewDbUtil.java
new file mode 100644
index 0000000000..aed97784fe
--- /dev/null
+++ b/java/com/google/gerrit/reviewdb/server/ReviewDbUtil.java
@@ -0,0 +1,77 @@
+// 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.reviewdb.server;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.common.collect.Ordering;
+import com.google.common.collect.Sets;
+import com.google.gwtorm.client.Column;
+import com.google.gwtorm.client.IntKey;
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.TreeSet;
+
+/** Static utilities for ReviewDb types. */
+public class ReviewDbUtil {
+  private static final Ordering<? extends IntKey<?>> INT_KEY_ORDERING =
+      Ordering.natural().nullsFirst().<IntKey<?>>onResultOf(IntKey::get).nullsFirst();
+
+  /**
+   * Null-safe ordering over arbitrary subclass of {@code IntKey}.
+   *
+   * <p>In some cases, {@code Comparator.comparing(Change.Id::get)} may be shorter and cleaner.
+   * However, this method may be preferable in some cases:
+   *
+   * <ul>
+   *   <li>This ordering is null-safe over both input and the result of {@link IntKey#get()}; {@code
+   *       comparing} is only a good idea if all inputs are obviously non-null.
+   *   <li>{@code intKeyOrdering().sortedCopy(iterable)} is shorter than the stream equivalent.
+   *   <li>Creating derived comparators may be more readable with {@link Ordering} method chaining
+   *       rather than static {@code Comparator} methods.
+   * </ul>
+   */
+  @SuppressWarnings("unchecked")
+  public static <K extends IntKey<?>> Ordering<K> intKeyOrdering() {
+    return (Ordering<K>) INT_KEY_ORDERING;
+  }
+
+  public static ReviewDb unwrapDb(ReviewDb db) {
+    if (db instanceof DisallowReadFromChangesReviewDbWrapper) {
+      return unwrapDb(((DisallowReadFromChangesReviewDbWrapper) db).unsafeGetDelegate());
+    }
+    return db;
+  }
+
+  public static void checkColumns(Class<?> clazz, Integer... expected) {
+    Set<Integer> ids = new TreeSet<>();
+    for (Field f : clazz.getDeclaredFields()) {
+      Column col = f.getAnnotation(Column.class);
+      if (col != null) {
+        ids.add(col.id());
+      }
+    }
+    Set<Integer> expectedIds = Sets.newTreeSet(Arrays.asList(expected));
+    checkState(
+        ids.equals(expectedIds),
+        "Unexpected column set for %s: %s != %s",
+        clazz.getSimpleName(),
+        ids,
+        expectedIds);
+  }
+
+  private ReviewDbUtil() {}
+}