Add database index on patch_sets.revision

Without that index the PatchSetAccess.byRevision was always doing a
sequential table scan.

Change-Id: Ief351d56794589fa0e1804fac5a6c38fea67e23c

gerrit-reviewdb/src/main/resources/com/google/gerrit/reviewdb/server/index_generic.sql

@@ -100,6 +100,11 @@ CREATE INDEX patch_comment_drafts
 ON patch_comments (status, author_id);
 
 
+-- *********************************************************************
+-- PatchSetAccess
+CREATE INDEX patch_sets_byRevision
+ON patch_sets (revision);
+
 -- *********************************************************************
 -- PatchSetAncestorAccess
 --    @PrimaryKey covers: ancestorsOf

gerrit-reviewdb/src/main/resources/com/google/gerrit/reviewdb/server/index_postgres.sql

@@ -151,6 +151,11 @@ ON patch_comments (author_id)
 WHERE status = 'd';
 
 
+-- *********************************************************************
+-- PatchSetAccess
+CREATE INDEX patch_sets_byRevision
+ON patch_sets (revision);
+
 -- *********************************************************************
 -- PatchSetAncestorAccess
 --    @PrimaryKey covers: ancestorsOf

gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java

@@ -32,7 +32,7 @@ import java.util.List;
 /** A version of the database schema. */
 public abstract class SchemaVersion {
   /** The current schema version. */
-  public static final Class<Schema_93> C = Schema_93.class;
+  public static final Class<Schema_94> C = Schema_94.class;
 
   public static class Module extends AbstractModule {
     @Override

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_94.java

@@ -0,0 +1,38 @@
+// Copyright (C) 2014 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.schema;
+
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gwtorm.jdbc.JdbcSchema;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import java.sql.SQLException;
+import java.sql.Statement;
+
+public class Schema_94 extends SchemaVersion {
+  @Inject
+  Schema_94(Provider<Schema_93> prior) {
+    super(prior);
+  }
+
+  @Override
+  protected void migrateData(ReviewDb db, UpdateUI ui) throws SQLException {
+    try (Statement stmt = ((JdbcSchema) db).getConnection().createStatement()) {
+      stmt.execute("CREATE INDEX patch_sets_byRevision"
+          + " ON patch_sets (revision)");
+    }
+  }
+}