Rails migration - changing the attribute name of a model

Question

In my Rails model for Comment, I have attributesmessage, date attributes along created_at and updated_at attributes automatically provided by ActiveRecord::Migration via t.timestamps.

Currently the date attribute has values in db ( postgresql ) for comments table. I want to remove the date attribute in Comment model and while doing this want to update the comments db table values for created_at attribute with value in date attribute.

How do I go about this ?

Answer 1

You can write the rails code inside the migration file as below to update the column value.

Assuming datatype of column date is timestamp.

class RemoveDateFromComment < ActiveRecord::Migration
  def up
    Comment.all.each do |comment|
      comment.update(created_at: comment.date)
    end

    remove_column :comments, :date, :timestamp
  end

  def down
    add_column :comments, :date, :timestamp

    Comment.all.each do |comment|
      comment.update(date: comment.created_at)
    end
  end
end