Store reviewer field in the index

Prior to this change, draft changes in search results may have
resulted in touching the database, since ChangeControl#isDraftVisible
checks if the user is a reviewer, and there are not enough stored
fields to compute the reviewer set from the index. (We store approvals
on the current patch set, not all approvals; even the latter would be
insufficient with NoteDb.)

Add a new reviewer field that stores enough information to reconstruct
the whole ReviewerSet, and also to search by reviewer state. Shove
this all in one repeated field with a little comma-separated format,
similar to what we already do for labels. The current
ReviewerPredicate implementation matches the old behavior of returning
results independent of state, although it's now expressed as a
predicate tree.

Change-Id: Ie54b9e2decf847185ec741bc50bae7eb680787a0

gerrit-server/src/test/java/com/google/gerrit/server/index/change/ChangeFieldTest.java

@@ -0,0 +1,73 @@
+// 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.index.change;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.HashBasedTable;
+import com.google.common.collect.Table;
+import com.google.gerrit.common.TimeUtil;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
+import com.google.gerrit.testutil.GerritBaseTests;
+import com.google.gerrit.testutil.TestTimeUtil;
+import com.google.gwtorm.client.KeyUtil;
+import com.google.gwtorm.server.StandardKeyEncoder;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.sql.Timestamp;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+public class ChangeFieldTest extends GerritBaseTests {
+  static {
+    KeyUtil.setEncoderImpl(new StandardKeyEncoder());
+  }
+
+  @Before
+  public void setUp() {
+    TestTimeUtil.resetWithClockStep(1, TimeUnit.SECONDS);
+  }
+
+  @After
+  public void tearDown() {
+    TestTimeUtil.useSystemTime();
+  }
+
+  @Test
+  public void reviewerFieldValues() {
+    Table<ReviewerStateInternal, Account.Id, Timestamp> t =
+        HashBasedTable.create();
+    Timestamp t1 = TimeUtil.nowTs();
+    t.put(ReviewerStateInternal.REVIEWER, new Account.Id(1), t1);
+    Timestamp t2 = TimeUtil.nowTs();
+    t.put(ReviewerStateInternal.CC, new Account.Id(2), t2);
+    ReviewerSet reviewers = ReviewerSet.fromTable(t);
+
+    List<String> values = ChangeField.getReviewerFieldValues(reviewers);
+    assertThat(values).containsExactly(
+        "REVIEWER,1",
+        "REVIEWER,1," + t1.getTime(),
+        "CC,2",
+        "CC,2," + t2.getTime());
+
+    assertThat(ChangeField.parseReviewerFieldValues(values))
+        .isEqualTo(reviewers);
+  }
+}

gerrit-server/src/test/java/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java

@@ -1397,6 +1397,26 @@ public abstract class AbstractQueryChangesTest extends GerritServerTests {
     assertThat(actual.get(1).reviewed).isTrue();
   }
 
+  @Test
+  public void reviewer() throws Exception {
+    TestRepository<Repo> repo = createProject("repo");
+    Change change1 = insert(repo, newChange(repo));
+    Change change2 = insert(repo, newChange(repo));
+    insert(repo, newChange(repo));
+
+    gApi.changes()
+      .id(change1.getId().get())
+      .current()
+      .review(ReviewInput.approve());
+    gApi.changes()
+      .id(change2.getId().get())
+      .current()
+      .review(ReviewInput.approve());
+
+    Account.Id id = user.getAccountId();
+    assertQuery("reviewer:" + id, change2, change1);
+  }
+
   @Test
   public void byCommitsOnBranchNotMerged() throws Exception {
     TestRepository<Repo> repo = createProject("repo");
@@ -1451,6 +1471,7 @@ public abstract class AbstractQueryChangesTest extends GerritServerTests {
     cd.currentApprovals();
     cd.changedLines();
     cd.reviewedBy();
+    cd.reviewers();
 
     // TODO(dborowitz): Swap out GitRepositoryManager somehow? Will probably be
     // necessary for NoteDb anyway.