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

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

activerecord/lib/active_record/base.rb

@@ -769,10 +769,24 @@ def destroy(id)
       #                         :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
 

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -153,6 +153,10 @@ def case_sensitive_equality_operator
         "="
       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.

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -523,6 +523,10 @@ def case_sensitive_equality_operator
         "= 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=)

activerecord/test/cases/base_test.rb

@@ -76,7 +76,7 @@ class TopicWithProtectedContentAndAccessibleAuthorName < ActiveRecord::Base
 end
 
 class BasicsTest < ActiveRecord::TestCase
-  fixtures :topics, :companies, :developers, :projects, :computers, :accounts, :minimalistics, 'warehouse-things', :authors, :categorizations, :categories
+  fixtures :topics, :companies, :developers, :projects, :computers, :accounts, :minimalistics, 'warehouse-things', :authors, :categorizations, :categories, :posts
 
   def test_table_exists
     assert !NonExistentTable.table_exists?
@@ -664,10 +664,21 @@ def test_update_all_with_order_and_limit
     end
   end
 
-  def test_update_all_ignores_order_limit_from_association
-    author = Author.find(1)
+  def test_update_all_ignores_order_without_limit_from_association
+    author = authors(:david)
     assert_nothing_raised do
-      assert_equal author.posts_with_comments_and_categories.length, author.posts_with_comments_and_categories.update_all("body = 'bulk update!'")
+      assert_equal author.posts_with_comments_and_categories.length, author.posts_with_comments_and_categories.update_all([ "body = ?", "bulk update!" ])
+    end
+  end
+
+  def test_update_all_with_order_and_limit_updates_subset_only
+    author = authors(:david)
+    assert_nothing_raised do
+      assert_equal 1, author.posts_sorted_by_id_limited.size
+      assert_equal 2, author.posts_sorted_by_id_limited.find(:all, :limit => 2).size
+      assert_equal 1, author.posts_sorted_by_id_limited.update_all([ "body = ?", "bulk update!" ])
+      assert_equal "bulk update!", posts(:welcome).body
+      assert_not_equal "bulk update!", posts(:thinking).body
     end
   end
 

activerecord/test/models/author.rb

@@ -2,6 +2,7 @@ class Author < ActiveRecord::Base
   has_many :posts, :accessible => true
   has_many :posts_with_comments, :include => :comments, :class_name => "Post"
   has_many :posts_with_comments_sorted_by_comment_id, :include => :comments, :class_name => "Post", :order => 'comments.id'
+  has_many :posts_sorted_by_id_limited, :class_name => "Post", :order => 'posts.id', :limit => 1
   has_many :posts_with_categories, :include => :categories, :class_name => "Post"
   has_many :posts_with_comments_and_categories, :include => [ :comments, :categories ], :order => "posts.id", :class_name => "Post"
   has_many :posts_containing_the_letter_a, :class_name => "Post"