Add indexes for user activity queries.

Closes #44446.

changelogs/unreleased/ab-44446-add-indexes-for-user-activity-queries.yml

+---
+title: Add indexes for user activity queries.
+merge_request: 17890
+author:
+type: performance

db/migrate/20180320182229_add_indexes_for_user_activity_queries.rb

+class AddIndexesForUserActivityQueries < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :events, [:project_id, :author_id]
+    add_concurrent_index :user_interacted_projects, :user_id
+  end
+
+  def down
+    remove_concurrent_index :events, [:project_id, :author_id]
+    remove_concurrent_index :user_interacted_projects, :user_id
+  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: 20180309160427) do
+ActiveRecord::Schema.define(version: 20180320182229) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -728,6 +728,7 @@ ActiveRecord::Schema.define(version: 20180309160427) do
 
   add_index "events", ["action"], name: "index_events_on_action", using: :btree
   add_index "events", ["author_id"], name: "index_events_on_author_id", using: :btree
+  add_index "events", ["project_id", "author_id"], name: "index_events_on_project_id_and_author_id", using: :btree
   add_index "events", ["project_id", "id"], name: "index_events_on_project_id_and_id", using: :btree
   add_index "events", ["target_type", "target_id"], name: "index_events_on_target_type_and_target_id", using: :btree
 
@@ -1863,6 +1864,7 @@ ActiveRecord::Schema.define(version: 20180309160427) do
   end
 
   add_index "user_interacted_projects", ["project_id", "user_id"], name: "index_user_interacted_projects_on_project_id_and_user_id", unique: true, using: :btree
+  add_index "user_interacted_projects", ["user_id"], name: "index_user_interacted_projects_on_user_id", using: :btree
 
   create_table "user_synced_attributes_metadata", force: :cascade do |t|
     t.boolean "name_synced", default: false