Support :limit on update_all so that has_many with :limit can be safely updated

Signed-off-by: Michael Koziarski <michael@koziarski.com>

3 files changed, 25 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index d7c67bc10d..fc6d762fcd 100644..100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -769,10 +769,24 @@ module ActiveRecord #:nodoc:
       #                         :order => 'created_at', :limit => 5 )
       def update_all(updates, conditions = nil, options = {})
         sql  = "UPDATE #{quoted_table_name} SET #{sanitize_sql_for_assignment(updates)} "
+
         scope = scope(:find)
-        add_conditions!(sql, conditions, scope)
-        add_order!(sql, options[:order], nil)
-        add_limit!(sql, options, nil)
+
+        select_sql = ""
+        add_conditions!(select_sql, conditions, scope)
+
+        if options.has_key?(:limit) || (scope && scope[:limit])
+          # Only take order from scope if limit is also provided by scope, this
+          # is useful for updating a has_many association with a limit.
+          add_order!(select_sql, options[:order], scope)
+
+          add_limit!(select_sql, options, scope)
+          sql.concat(connection.limited_update_conditions(select_sql, quoted_table_name, connection.quote_column_name(primary_key)))
+        else
+          add_order!(select_sql, options[:order], nil)
+          sql.concat(select_sql)
+        end
+
         connection.update(sql, "#{name} Update")
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index aaf9e2e73f..8fc89de22b 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -153,6 +153,10 @@ module ActiveRecord
         "="
       end
 
+      def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
+        "WHERE #{quoted_primary_key} IN (SELECT #{quoted_primary_key} FROM #{quoted_table_name} #{where_sql})"
+      end
+
       protected
         # Returns an array of record hashes with the column names as keys and
         # column values as values.
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index f1d13698c3..c2a0fb72bf 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -523,6 +523,10 @@ module ActiveRecord
         "= BINARY"
       end
 
+      def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
+        where_sql
+      end
+
       private
         def connect
           @connection.reconnect = true if @connection.respond_to?(:reconnect=)