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ActiveRecord marshal dump/load has a different behavior on boolean [rails]

#5381

Step 1: setup

a = Aritcle.new(:some_boolean => false)
a.save
write_to_memcache(a.id, Marshal.dump(a))
b = Marshal.load(read_from_memcache(a.id))

If I do:

b.some_boolean = nil
b.save

the some_boolean is not written back to the DB. DB still remains false.

But:

a.some_boolean = nil
a.save

works perfectly. DB is set to NULL.

Also:

c = Article.find(a.id)
c.some_boolean = nil
c.save

works fine. DB is set to NULL.

I'm not very sure if this is a boolean specific problem, but I'm thinking rails has some private variable to detect if the record is new, and the marshal is screwing it up.

Any hints? This one was a tough nut to crack on production :) Thanks.

Reported by prasanna · August 14th, 2010 @ 07:45 PM

Activity

prasanna
- Assigned user set to Aaron Patterson
I was wondering if this should be a bug report of a ticket?

August 14th, 2010 @ 07:52 PM
Aaron Patterson
- State changed from new to needs-more-info
- Importance changed from to Low
I can't seem to reproduce this problem. What database are you using? What version of Rails? Can you share your schema?

Even better would be if you could supply a small rails app that reproduces the problem. I would really appreciate that! :-D

I've tried adding the following test to the AR test cases, but cannot reproduce the problem:
```
class Booleantest < ActiveRecord::Base; end

def test_saving_after_marshal
  bool = Booleantest.new(:value => false)
  bool = Marshal.load Marshal.dump bool
  bool.value = nil
  bool.save
  bool.reload
  assert_nil bool.value
end
```
August 16th, 2010 @ 06:37 PM
prasanna
DataBase: mysql
Rails: 2.3.5

To reproduce it: You have to put the following statement in your after_save handler.
```
class Bool

  after_save :dumper

  def dumper
    $global = Marshal.load Marshal.dump self
  end

end

Bool.new(:value => false).save
puts $global.value # is false -> OK

$global.value = nil
$global.save
puts $global.value # is nil -> OK

$global.reload
puts $global.value # is false -> BAD
```
I owe you an apology for not testing Marshal.load Marshal.dump sequence. I was binary-searching the problem and this is what I got it down to. If you need any more info, or if you are unable to reproduce this, feel free to ping me. myprasanna@gmail.com
August 16th, 2010 @ 08:11 PM
prasanna
It is probably not a deal-breaker. I am guessing, rails works like this:
```
@after_save_running = true
# call the after_save handlers
@after_save_running = false
```
And since I dump in the after_save handler, that variable gets dumped as true. The next time I try to save it fails, to do it, thinking the after_save handler is calling a save function, causing recursion. I think you can safely close this.

Thanks for your time.
August 16th, 2010 @ 08:21 PM
Aaron Patterson
- State changed from needs-more-info to invalid
November 4th, 2010 @ 10:10 PM
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March 26th, 2011 @ 02:02 AM