Re-organise "issues" indexes for faster ordering

changelogs/unreleased/reorganise-issues-indexes-for-sorting.yml

+---
+title: Re-organise "issues" indexes for faster ordering
+merge_request:
+author:

db/migrate/20170803130232_reorganise_issues_indexes_for_faster_sorting.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class ReorganiseIssuesIndexesForFasterSorting < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  REMOVE_INDEX_COLUMNS = %i[project_id created_at due_date updated_at].freeze
+
+  ADD_INDEX_COLUMNS = [
+    %i[project_id created_at id state],
+    %i[project_id due_date id state],
+    %i[project_id updated_at id state]
+  ].freeze
+
+  TABLE = :issues
+
+  def up
+    add_indexes(ADD_INDEX_COLUMNS)
+    remove_indexes(REMOVE_INDEX_COLUMNS)
+  end
+
+  def down
+    add_indexes(REMOVE_INDEX_COLUMNS)
+    remove_indexes(ADD_INDEX_COLUMNS)
+  end
+
+  def add_indexes(columns)
+    columns.each do |column|
+      add_concurrent_index(TABLE, column) unless index_exists?(TABLE, column)
+    end
+  end
+
+  def remove_indexes(columns)
+    columns.each do |column|
+      remove_concurrent_index(TABLE, column) if index_exists?(TABLE, column)
+    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: 20170728101014) do
+ActiveRecord::Schema.define(version: 20170803130232) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -641,12 +641,13 @@ ActiveRecord::Schema.define(version: 20170728101014) do
   add_index "issues", ["assignee_id"], name: "index_issues_on_assignee_id", using: :btree
   add_index "issues", ["author_id"], name: "index_issues_on_author_id", using: :btree
   add_index "issues", ["confidential"], name: "index_issues_on_confidential", using: :btree
-  add_index "issues", ["created_at"], name: "index_issues_on_created_at", using: :btree
   add_index "issues", ["deleted_at"], name: "index_issues_on_deleted_at", using: :btree
   add_index "issues", ["description"], name: "index_issues_on_description_trigram", using: :gin, opclasses: {"description"=>"gin_trgm_ops"}
-  add_index "issues", ["due_date"], name: "index_issues_on_due_date", using: :btree
   add_index "issues", ["milestone_id"], name: "index_issues_on_milestone_id", using: :btree
+  add_index "issues", ["project_id", "created_at", "id", "state"], name: "index_issues_on_project_id_and_created_at_and_id_and_state", using: :btree
+  add_index "issues", ["project_id", "due_date", "id", "state"], name: "index_issues_on_project_id_and_due_date_and_id_and_state", using: :btree
   add_index "issues", ["project_id", "iid"], name: "index_issues_on_project_id_and_iid", unique: true, using: :btree
+  add_index "issues", ["project_id", "updated_at", "id", "state"], name: "index_issues_on_project_id_and_updated_at_and_id_and_state", using: :btree
   add_index "issues", ["relative_position"], name: "index_issues_on_relative_position", using: :btree
   add_index "issues", ["state"], name: "index_issues_on_state", using: :btree
   add_index "issues", ["title"], name: "index_issues_on_title_trigram", using: :gin, opclasses: {"title"=>"gin_trgm_ops"}