Merge pull request #6985 from sidonath/disable-query-cache-for-locks

Disable query cache for lock queries
Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb

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

@@ -56,7 +56,7 @@ module ActiveRecord
       end
 
       def select_all(arel, name = nil, binds = [])
-        if @query_cache_enabled
+        if @query_cache_enabled && !locked?(arel)
           sql = to_sql(arel, binds)
           cache_sql(sql, binds) { super(sql, name, binds) }
         else
@@ -77,6 +77,14 @@ module ActiveRecord
 
           result.collect { |row| row.dup }
         end
+
+        def locked?(arel)
+          if arel.respond_to?(:locked)
+            arel.locked
+          else
+            false
+          end
+        end
     end
   end
 end

activerecord/test/cases/query_cache_test.rb

@@ -165,6 +165,14 @@ class QueryCacheTest < ActiveRecord::TestCase
       end
     end
   end
+
+  def test_cache_is_ignored_for_locked_relations
+    task = Task.find 1
+
+    Task.cache do
+      assert_queries(2) { task.lock!; task.lock! }
+    end
+  end
 end
 
 class QueryCacheExpiryTest < ActiveRecord::TestCase