Create index on environments project_id, state, environment_type

Replace index on environments project_id and state

changelogs/unreleased/add-index-on-environment-type.yml

+---
+title: Replace index on environments table project_id and state with project_id, state, and environment_type
+merge_request: 19902
+author:
+type: performance

db/migrate/20191118182722_add_index_to_environments_on_project_id_state_environment_type.rb

+# frozen_string_literal: true
+
+class AddIndexToEnvironmentsOnProjectIdStateEnvironmentType < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  OLD_INDEX_NAME = 'index_environments_on_project_id_and_state'.freeze
+  NEW_INDEX_NAME = 'index_environments_on_project_id_state_environment_type'.freeze
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index(:environments, [:project_id, :state, :environment_type], name: NEW_INDEX_NAME)
+    remove_concurrent_index_by_name(:environments, OLD_INDEX_NAME)
+  end
+
+  def down
+    add_concurrent_index(:environments, [:project_id, :state], name: OLD_INDEX_NAME)
+    remove_concurrent_index_by_name(:environments, NEW_INDEX_NAME)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_11_15_091425) do
+ActiveRecord::Schema.define(version: 2019_11_18_182722) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -1435,7 +1435,7 @@ ActiveRecord::Schema.define(version: 2019_11_15_091425) do
     t.index ["name"], name: "index_environments_on_name_varchar_pattern_ops", opclass: :varchar_pattern_ops
     t.index ["project_id", "name"], name: "index_environments_on_project_id_and_name", unique: true
     t.index ["project_id", "slug"], name: "index_environments_on_project_id_and_slug", unique: true
-    t.index ["project_id", "state"], name: "index_environments_on_project_id_and_state"
+    t.index ["project_id", "state", "environment_type"], name: "index_environments_on_project_id_state_environment_type"
   end
 
   create_table "epic_issues", id: :serial, force: :cascade do |t|