Add index for ci_builds that makes shared runners query to run 50x faster.

db/migrate/20170121123724_add_index_to_ci_builds_for_status_runner_id_and_type.rb

+class AddIndexToCiBuildsForStatusRunnerIdAndType < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :ci_builds, [:status, :type, :runner_id]
+  end
+
+  def down
+    if index_exists?(:ci_builds, [:status, :type, :runner_id])
+      remove_index :ci_builds, column: [:status, :type, :runner_id]
+    end
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170106172224) do
+ActiveRecord::Schema.define(version: 20170121123724) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -224,6 +224,7 @@ ActiveRecord::Schema.define(version: 20170106172224) do
   add_index "ci_builds", ["gl_project_id"], name: "index_ci_builds_on_gl_project_id", using: :btree
   add_index "ci_builds", ["project_id"], name: "index_ci_builds_on_project_id", using: :btree
   add_index "ci_builds", ["runner_id"], name: "index_ci_builds_on_runner_id", using: :btree
+  add_index "ci_builds", ["status", "type", "runner_id"], name: "index_ci_builds_on_status_and_type_and_runner_id", using: :btree
   add_index "ci_builds", ["status"], name: "index_ci_builds_on_status", using: :btree
   add_index "ci_builds", ["token"], name: "index_ci_builds_on_token", unique: true, using: :btree