Explain that default_scope also influences update_all

This was not explicitly stated before and I needed to try it out to be
certain. A little explicit statement in the API docs might help here.

1 files changed, 12 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 460daf99bc..fc3306ee81 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -304,11 +304,12 @@ module ActiveRecord
       klass.current_scope = previous
     end
 
-    # Updates all records with details given if they match a set of conditions supplied, limits and order can
-    # also be supplied. This method constructs a single SQL UPDATE statement and sends it straight to the
-    # database. It does not instantiate the involved models and it does not trigger Active Record callbacks
-    # or validations. Values passed to `update_all` will not go through ActiveRecord's type-casting behavior.
-    # It should receive only values that can be passed as-is to the SQL database.
+    # Updates all records in the current scope (respecting the <tt>default_scope</tt>, <tt>where</tt>,
+    # <tt>limit</tt> and <tt>order</tt> specified) with details given. This method constructs a single SQL update_all
+    # statement and sends it straight to the database. It does not instantiate the involved models and it does not
+    # trigger Active Record callbacks or validations. Values passed to `update_all` will not go through
+    # ActiveRecord's type-casting behavior. It should receive only values that can be passed as-is to the SQL
+    # database.
     #
     # ==== Parameters
     #
@@ -319,6 +320,12 @@ module ActiveRecord
     #   # Update all customers with the given attributes
     #   Customer.update_all wants_email: true
     #
+    #   # Update all active accounts with the given attributes
+    #   class Account < ActiveRecord::Base
+    #     default_scope -> { where active: true }
+    #   end
+    #   Account.update_all(failed_logins: 0)
+    #
     #   # Update all books with 'Rails' in their title
     #   Book.where('title LIKE ?', '%Rails%').update_all(author: 'David')
     #