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, 13 insertions, 5 deletions

diff --git a/activerecord/test/cases/integration_test.rb b/activerecord/test/cases/integration_test.rb
index 9169207b0a..08a186ae07 100644
--- a/activerecord/test/cases/integration_test.rb
+++ b/activerecord/test/cases/integration_test.rb
@@ -81,7 +81,7 @@ class IntegrationTest < ActiveRecord::TestCase
 
   def test_cache_key_format_for_existing_record_with_updated_at
     dev = Developer.first
-    assert_equal "developers/#{dev.id}-#{dev.updated_at.utc.to_s(:nsec)}", dev.cache_key
+    assert_equal "developers/#{dev.id}-#{dev.updated_at.utc.to_s(:usec)}", dev.cache_key
   end
 
   def test_cache_key_format_for_existing_record_with_updated_at_and_custom_cache_timestamp_format
@@ -111,19 +111,19 @@ class IntegrationTest < ActiveRecord::TestCase
   def test_cache_key_for_updated_on
     dev = Developer.first
     dev.updated_at = nil
-    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:nsec)}", dev.cache_key
+    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:usec)}", dev.cache_key
   end
 
   def test_cache_key_for_newer_updated_at
     dev = Developer.first
     dev.updated_at += 3600
-    assert_equal "developers/#{dev.id}-#{dev.updated_at.utc.to_s(:nsec)}", dev.cache_key
+    assert_equal "developers/#{dev.id}-#{dev.updated_at.utc.to_s(:usec)}", dev.cache_key
   end
 
   def test_cache_key_for_newer_updated_on
     dev = Developer.first
     dev.updated_on += 3600
-    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:nsec)}", dev.cache_key
+    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:usec)}", dev.cache_key
   end
 
   def test_cache_key_format_is_precise_enough
@@ -134,8 +134,16 @@ class IntegrationTest < ActiveRecord::TestCase
     assert_not_equal key, dev.cache_key
   end
 
+  def test_cache_key_format_is_not_too_precise
+    skip("Subsecond precision is not supported") unless subsecond_precision_supported?
+    dev = Developer.first
+    dev.touch
+    key = dev.cache_key
+    assert_equal key, dev.reload.cache_key
+  end
+
   def test_named_timestamps_for_cache_key
     owner = owners(:blackbeard)
-    assert_equal "owners/#{owner.id}-#{owner.happy_at.utc.to_s(:nsec)}", owner.cache_key(:updated_at, :happy_at)
+    assert_equal "owners/#{owner.id}-#{owner.happy_at.utc.to_s(:usec)}", owner.cache_key(:updated_at, :happy_at)
   end
 end