[Rails] CSV problem with migration but working fine in controller

I'm getting problem with csv. When I use below code in my Controller
method then it works but when I put this in my migration then this don't
work. Why so

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In My Controller's index method. It works.


require 'csv'

CSV.foreach("#{Rails.root}/db/adwords_location_data/languages.csv")
do |row|
obj_language = Language.new
obj_language.name = row[1]
obj_language.adwords_id = row[0]
obj_language.save
end

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But When I write this in my migration this doesn't work. No error come
but data didn't inserted in the tables. Below is the migration code.

require "csv"

class LoadLanguageData < ActiveRecord::Migration
def self.up
CSV.foreach("#{Rails.root}/db/adwords_location_data/languages.csv") do
obj_language = Language.new
obj_language.name = row[1]
obj_language.adwords_id = row[0]
obj_language.save
end
end

def self.down
Language.destroy_all
end
end