fixes #21815

The default timestamp used for AR is `updated_at` in nanoseconds! (:nsec) This causes issues on any machine that runs an OS that supports nanoseconds timestamps, i.e. not-OS X, where the cache_key of the record persisted in the database (milliseconds precision) is out-of-sync with the cache_key in the ruby VM.

This commit adds:

A test that shows the issue, it can be found in the separate file `cache_key_test.rb`, because
- model couldn't be defined inline
- transactional testing needed to be turned off to get it to pass the MySQL tests
This seemed cleaner than putting it in an existing testcase file.

It adds :usec as a dateformat that calculates datetime in microseconds

It sets precision of cache_key to :usec instead of :nsec, as no db supports nsec precision on timestamps

1 files changed, 1 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/time/conversions.rb b/activesupport/lib/active_support/core_ext/time/conversions.rb
index eecbac2c20..536c4bf525 100644
--- a/activesupport/lib/active_support/core_ext/time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/time/conversions.rb
@@ -6,6 +6,7 @@ class Time
     :db           => '%Y-%m-%d %H:%M:%S',
     :number       => '%Y%m%d%H%M%S',
     :nsec         => '%Y%m%d%H%M%S%9N',
+    :usec         => '%Y%m%d%H%M%S%6N',
     :time         => '%H:%M',
     :short        => '%d %b %H:%M',
     :long         => '%B %d, %Y %H:%M',