Monday, February 16, 2009

Frustrated with change_column Rails 2.1.2

My team tried upgrading from Rails 2.1.0 to 2.1.2 and ran into a few frustrating problems. When we first defined our tables in rails 1.2.6 we used "string" data types for certain columns:
create_table :widgets do |t|
t.string :form_data, :default=>"" :null=>false

A few months went by and we decided to upgrade from 1.2.6 to 2.1.0 but it required us to change from strings to text fields. The migration script looked like this:
change_column(:widgets, :form_data, :text, :default=>"")
In Rails 2.1.2 the change_column function retained its nullability unless you explicitly requested it, however in 2.1.0 it would always redefine it to the defaul null => true. Tailing the logs confirmed this subtle difference:
2.1.0 => ALTER TABLE widgets CHANGE COLUMN form_data text DEFAULT '' NOT NULL
2.1.2 => ALTER TABLE widgets CHANGE COLUMN form_data text DEFAULT ''
We then had to create another migration so that we would be in sync with our production database:
change_column(:widgets, :form_data, :text, {:default=>"", :null => true })
Annoying but true.

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