Include other cols in index for pending builds

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/327142

Changelog: performance

changelogs/unreleased/ab-ci-builds-pending-partial-covering.yml

+---
+title: Include other cols in index for pending builds
+merge_request: 60997
+author:
+type: performance

db/post_migrate/20210505092746_create_partial_covering_index_for_pending_builds.rb

+# frozen_string_literal: true
+
+class CreatePartialCoveringIndexForPendingBuilds < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  EXISTING_INDEX = 'index_ci_builds_runner_id_pending'
+  NEW_INDEX = 'index_ci_builds_runner_id_pending_covering'
+
+  def up
+    execute "CREATE INDEX CONCURRENTLY #{NEW_INDEX} ON ci_builds (runner_id, id) INCLUDE (project_id) WHERE status = 'pending' AND type = 'Ci::Build'" unless index_exists_by_name?(:ci_builds, NEW_INDEX)
+
+    remove_concurrent_index_by_name :ci_builds, EXISTING_INDEX
+  end
+
+  def down
+    add_concurrent_index :ci_builds, :runner_id, where: "status = 'pending' AND type = 'Ci::Build'", name: EXISTING_INDEX
+    remove_concurrent_index_by_name :ci_builds, NEW_INDEX
+  end
+end

db/schema_migrations/20210505092746

+ccf7bce753adabfd7dd8a68fd49853514367f11af42879cae1b6aa28e4ebe94c
\ No newline at end of file

db/structure.sql

@@ -22389,7 +22389,7 @@ CREATE INDEX index_ci_builds_on_user_id_and_created_at_and_type_eq_ci_build ON c
 
 CREATE INDEX index_ci_builds_project_id_and_status_for_live_jobs_partial2 ON ci_builds USING btree (project_id, status) WHERE (((type)::text = 'Ci::Build'::text) AND ((status)::text = ANY (ARRAY[('running'::character varying)::text, ('pending'::character varying)::text, ('created'::character varying)::text])));
 
-CREATE INDEX index_ci_builds_runner_id_pending ON ci_builds USING btree (runner_id) WHERE (((status)::text = 'pending'::text) AND ((type)::text = 'Ci::Build'::text));
+CREATE INDEX index_ci_builds_runner_id_pending_covering ON ci_builds USING btree (runner_id, id) INCLUDE (project_id) WHERE (((status)::text = 'pending'::text) AND ((type)::text = 'Ci::Build'::text));
 
 CREATE INDEX index_ci_builds_runner_id_running ON ci_builds USING btree (runner_id) WHERE (((status)::text = 'running'::text) AND ((type)::text = 'Ci::Build'::text));