Add index for issues on relative position, project

and state

app/models/issue.rb

@@ -131,7 +131,7 @@ class Issue < ApplicationRecord
     when 'due_date'            then order_due_date_asc
     when 'due_date_asc'        then order_due_date_asc
     when 'due_date_desc'       then order_due_date_desc
-    when 'relative_position'   then order_relative_position_asc
+    when 'relative_position'   then order_relative_position_asc.with_order_id_desc
     else
       super
     end

changelogs/unreleased/bw-add-index-for-relative-position.yml

+---
+title: Add index for issues on relative position, project, and state for manual sorting
+merge_request: 30542
+author:
+type: fixed

db/migrate/20190709220143_add_index_to_issues_relative_position.rb

+# frozen_string_literal: true
+
+class AddIndexToIssuesRelativePosition < ActiveRecord::Migration[5.1]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_issues_on_project_id_and_state_and_rel_position_and_id'.freeze
+
+  def up
+    add_concurrent_index :issues, [:project_id, :state, :relative_position, :id], order: { id: :desc }, name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :issues, INDEX_NAME
+  end
+end

db/schema.rb

@@ -1682,6 +1682,7 @@ ActiveRecord::Schema.define(version: 2019_07_15_114644) do
     t.index ["project_id", "created_at", "id", "state"], name: "index_issues_on_project_id_and_created_at_and_id_and_state", using: :btree
     t.index ["project_id", "due_date", "id", "state"], name: "idx_issues_on_project_id_and_due_date_and_id_and_state_partial", where: "(due_date IS NOT NULL)", using: :btree
     t.index ["project_id", "iid"], name: "index_issues_on_project_id_and_iid", unique: true, using: :btree
+    t.index ["project_id", "state", "relative_position", "id"], name: "index_issues_on_project_id_and_state_and_rel_position_and_id", order: { id: :desc }, using: :btree
     t.index ["project_id", "updated_at", "id", "state"], name: "index_issues_on_project_id_and_updated_at_and_id_and_state", using: :btree
     t.index ["relative_position"], name: "index_issues_on_relative_position", using: :btree
     t.index ["state"], name: "index_issues_on_state", using: :btree