heroku: PG::InvalidTextRepresentation: ERROR: invalid input syntax for integer: “” - ruby-on-rails

Question

I have a currency(ccy) column on my event model and it's currently a string, I'd like to change it to a integer.
Although it works on my local environment, the following error was displayed when I try heroku run rake db:migrate to heroku.
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::InvalidTextRepresentation: ERROR: invalid input syntax for integer: ""
: ALTER TABLE "events" ALTER COLUMN "ccy" TYPE integer USING CAST(ccy AS integer)
The migration file as below.
class ChangeCcyToEvents < ActiveRecord::Migration
def change
change_column :events, :ccy, 'integer USING CAST(ccy AS integer)'
end
end
I found the similar question PG::InvalidTextRepresentation: ERROR: invalid input syntax for integer: "M", so I changed migration file as below. But the result is the same.
class ChangeCcyToEvents < ActiveRecord::Migration
def change
Event.where(ccy: '').update_all(ccy: '')
change_column :events, :ccy, 'integer USING CAST(ccy AS integer)'
end
end
There is no value in all ccy column so far.
It would be appreciated if you could give me any advice.

Answer 1

Your migration is trying to convert a "" into an integer, which postgres complais about it (and it should, because it's not a valid conversion).
You should update your content for invalid cases before changing the column type:
class ChangeCcyToEvents < ActiveRecord::Migration
def up
Event.where("ccy IS NULL OR ccy = ''").update_all({ccy: '0'})
change_column :events, :ccy, 'integer USING CAST(ccy AS integer)'
end
def down
raise ActiveRecord::IrreversibleMigration
end
end
Perhaps is not complaining in development (localhost) because you're using a different version of postgreSQL than Heroku.
Next time, try using default values in migrations for this kind of columns.