Hello everyone, just wondering if anyone can help me with a migrations
question here.
Using:
rails 2.0.2
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin]
mysql 5.0.45
Platform:
windows xp
The problem:
I created a migration that is designed to add a column named
“deleted_at” (timestamp) and then remove a column named
“is_deleted” (boolean). The idea is to upgrade from merely tracking
whether a record has been non-destructively deleted to tracking both
if and when it has been non-destructively deleted. NULL values in
“deleted_at” indicate a normal, non-deleted record.
The trick and problem is to keep existing records’ is/isn’t deleted
state valid while doing the migration. In order to accomplish this, I
tried to add code after the “add_column” that creates “deleted_at” and
before the “remove_column” that removes the “is_deleted” column to do
this. The code I wrote checks all records and sets “deleted_at” to
“Time.now” if the “is_deleted” field is true. Or, at least that’s the
idea.
Unfortunately, the code to update the field has no effect.
Can someone tell me why?
For completeness, I created a simple test rails application (bugtest)
to demonstrate. The applicable files/code are as follows:
bugtest/db/migrate/001_create_options.rb <— Original table
definition
class CreateOptions < ActiveRecord::Migration
def self.up
create_table :options do |t|
t.string :name
t.boolean :is_deleted, :default => false, :null => false
t.timestamps
end
end
def self.down
drop_table :options
end
end
bugtest/db/migrate/002_add_deleted_at_to_options.rb <— Upgrade
migration that doesn’t completely work
class AddDeletedAtToOptions < ActiveRecord::Migration
Create temp model to use…
class Option < ActiveRecord::Base; end
Add deleted_at column, set to Time.now if is_deleted is true,
then remove is_deleted:
def self.up
add_column(:options, :deleted_at, :timestamp, :default => nil)
say “IN TABLE option: Setting deleted_at to now if is_deleted
set.” do
Option.reset_column_information
Option.find(:all).each do |option|
option.update_attribute(:deleted_at, Time.now) if
option[:is_deleted]
end
end
remove_column(:options, :is_deleted)
end
Add is_deleted column, set to true if deleted_at isn’t NULL,
then remove deleted_at
def self.down
add_column(:options, :is_deleted, :boolean, :default =>
false, :null => false)
say “IN TABLE option: Setting is_deleted to true if deleted_at
set.” do
Option.reset_column_information
Option.find(:all).each do |option|
option.update_attribute(:is_deleted, true) unless
option[:deleted_at] == nil
end
end
remove_column(:options, :deleted_at)
end
end
bugtest/test/fixtures/options.yml <— Test records that demonstrate
the issue
one:
name: “Record Not Deleted”
is_deleted: false
two:
name: “Deleted Record”
is_deleted: true
Sequence of commands executed and observations:
rake db:create
rake db:migrate VERSION=1
rake db:fixtures:load
Check out data in database, looks good. One record marked as deleted
and one isn’t.
rake db:migrate
Command reports everything working. Checked database, however, and the
“deleted_at” field for both records is NULL. I expected the record
that originally had “is_deleted” set to true to have a timestamp value
in “deleted_at” instead of NULL.
Well, there you have it. Any help or enlightenment is greatly
appreciated.
–
Kendall G.
zettabyte a t g mail dawt cawm