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TimeWithZone comparison fails for distinct instances of same time
Reported by Ari Epstein | August 30th, 2009 @ 03:05 PM
Let's say I have a model "Role" with timestamps and a string name attribute. I want to do some time comparisons. Here's the expected versus actual that I see:
Expected:
r = Role.create(:name => 'a role')
initial=r.created_at
r.reload
initial==r.created_at
=> true
Actual:
r=Role.create(:name => 'a role') => # initial = r.created_at => Sun, 30 Aug 2009 09:46:14 EDT -04:00 r.reload => # r.created_at == initial => false
I've tried <=>, converting to other types (Time, DateTime), and the comparison always fails. What's going on?
Comments and changes to this ticket
-
Ari Epstein August 30th, 2009 @ 03:05 PM
- Tag set to “activesupport, datetime, time, timewithzone”
-
Matt Duncan August 30th, 2009 @ 05:12 PM
I was unable to reproduce this on master.
Loading development environment (Rails 3.0.pre) >> r = Role.create(:name => 'a role') => #<Role id: 2, name: "a role", created_at: "2009-08-30 16:10:18", updated_at: "2009-08-30 16:10:18"> >> initial = r.created_at => Sun, 30 Aug 2009 16:10:18 UTC +00:00 >> r.reload => #<Role id: 2, name: "a role", created_at: "2009-08-30 16:10:18", updated_at: "2009-08-30 16:10:18"> >> initial == r.created_at => true -
Matt Jones September 5th, 2009 @ 05:42 AM
I've seen this happen in tests before - typically caused by the database having a different time resolution than the system. So even though the two times print identically, one is really (for instance) 15:45:32.012445362 and the DB loads back 15:45:32, which doesn't compare as equal.
-
JackC October 5th, 2009 @ 07:47 PM
Just ran into this in tests myself. You can determine the usec method to see the difference. I worked around this in my tests by specifying times instead of using the current time.
-
Geoff Buesing October 27th, 2009 @ 02:34 AM
- State changed from “new” to “invalid”
Matt Jones is probably right; this looks to be an issue with the database not storing usec.
In your tests, you can try coercing to_a before comparing; usec value isn't returned in the to_a representation:
assert_equal initial.to_a, r.created_at.to_a
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Ari Epstein
Geoff Buesing
Matt Duncan