Add index to events and audit_events tables

Index on created_at, author_id

db/post_migrate/20190611161642_add_index_to_events_and_audit_events_created_at_author_id.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddIndexToEventsAndAuditEventsCreatedAtAuthorId < ActiveRecord::Migration[5.1]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  INDEX_NAME = 'analytics_index_%s_on_created_at_and_author_id'.freeze
+  EVENTS_INDEX_NAME = (INDEX_NAME % 'events').freeze
+  AUDIT_EVENTS_INDEX_NAME = (INDEX_NAME % 'audit_events').freeze
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :events, [:created_at, :author_id], name: EVENTS_INDEX_NAME
+    add_concurrent_index :audit_events, [:created_at, :author_id], name: AUDIT_EVENTS_INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :events, EVENTS_INDEX_NAME
+    remove_concurrent_index_by_name :audit_events, AUDIT_EVENTS_INDEX_NAME
+  end
+end

db/schema.rb

@@ -335,6 +335,7 @@ ActiveRecord::Schema.define(version: 20190613030606) do
     t.text "details"
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.index ["created_at", "author_id"], name: "analytics_index_audit_events_on_created_at_and_author_id", using: :btree
     t.index ["entity_id", "entity_type"], name: "index_audit_events_on_entity_id_and_entity_type", using: :btree
   end
 
@@ -1219,6 +1220,7 @@ ActiveRecord::Schema.define(version: 20190613030606) do
     t.string "target_type"
     t.index ["action"], name: "index_events_on_action", using: :btree
     t.index ["author_id", "project_id"], name: "index_events_on_author_id_and_project_id", using: :btree
+    t.index ["created_at", "author_id"], name: "analytics_index_events_on_created_at_and_author_id", using: :btree
     t.index ["project_id", "created_at"], name: "index_events_on_project_id_and_created_at", using: :btree
     t.index ["project_id", "id"], name: "index_events_on_project_id_and_id", using: :btree
     t.index ["target_type", "target_id"], name: "index_events_on_target_type_and_target_id", using: :btree