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Multiple assignments to same column due to duplicate keys in @changed_attributes #110

merged 3 commits into from Jun 8, 2012


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jnv commented Jun 4, 2012

I've encountered quite rare problem with CPK while using Devise or CarrierWave. Under some conditions, @changed_attributes hash (used by AttributeMethods::Dirty) can contain duplicated attributes – symbol and string. See ce7eb75 for straightforward example. In the end, the resulting query contains 2 assignments to the same field:

UPDATE "reference_types" SET "abbreviation" = 'b', "abbreviation" = 'b' WHERE "reference_types"."reference_type_id" = 1

The funny part is that most DB systems happily accept such query. PostgreSQL does not.

Rails already prevent this by conversion of attribute key to string (ee6aa8f).
I also had to fix some associations test since the hash from ActiveModel::Dirty#changes uses string keys for assertion (56df46c) – otherwise this shouldn't affect anyone since this method returns a HashWithIndifferentAccess.

Anyway, I think that the preferred solution would be to call the original method, since both are basically same (except for intercepting an Array).
I'm not sure how to do it since I don't understand how the method is overridden in this case – alias :[]= :write_attribute doesn't ring any bells.

@cfis cfis added a commit that referenced this pull request Jun 8, 2012

@cfis cfis Merge pull request #110 from jnv/write_attribute
Multiple assignments to same column due to duplicate keys in @changed_attributes

@cfis cfis merged commit d558e89 into composite-primary-keys:master Jun 8, 2012


cfis commented Jun 8, 2012

Thanks for the patch.

alias :[]= :write_attribute is something ActiveRecord already does. We have to reapply it though since we override the write_attribute method.

It maps foo[:bar] = 1 to foo.write_attribute(:bar, 1)


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