Merge branch 'ak/add-index-on-builds' into 'master'

Improve ci_builds runner_id index

See merge request gitlab-org/gitlab!48241

changelogs/unreleased/ak-add-index-on-builds.yml

+---
+title: Adds id desc to index_ci_builds_on_runner_id_and_id_desc
+merge_request: 48241
+author:
+type: fixed

db/post_migrate/20201120140210_add_runner_id_and_id_desc_index_to_ci_builds.rb

+# frozen_string_literal: true
+
+class AddRunnerIdAndIdDescIndexToCiBuilds < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  NEW_INDEX = 'index_ci_builds_on_runner_id_and_id_desc'
+  OLD_INDEX = 'index_ci_builds_on_runner_id'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :ci_builds, %i[runner_id id], name: NEW_INDEX, order: { id: :desc }
+    remove_concurrent_index_by_name :ci_builds, OLD_INDEX
+  end
+
+  def down
+    add_concurrent_index :ci_builds, %i[runner_id], name: OLD_INDEX
+    remove_concurrent_index_by_name :ci_builds, NEW_INDEX
+  end
+end

db/schema_migrations/20201120140210

+6b88d79aa8d373fa1d9aa2698a9d20c09aff14ef16af4c123abd4e7c98e41311
\ No newline at end of file

db/structure.sql

@@ -20482,7 +20482,7 @@ CREATE INDEX index_ci_builds_on_protected ON ci_builds USING btree (protected);
 
 CREATE INDEX index_ci_builds_on_queued_at ON ci_builds USING btree (queued_at);
 
-CREATE INDEX index_ci_builds_on_runner_id ON ci_builds USING btree (runner_id);
+CREATE INDEX index_ci_builds_on_runner_id_and_id_desc ON ci_builds USING btree (runner_id, id DESC);
 
 CREATE INDEX index_ci_builds_on_stage_id ON ci_builds USING btree (stage_id);