Add timestamps to an existing table

Question

I need to add timestamps (created_at & updated_at) to an existing table. I tried the following code but it didn\'t work.

class          


        

Answer 1

add_timestamps(table_name, options = {}) public

Adds timestamps (created_at and updated_at) columns to table_name. Additional options (like null: false) are forwarded to #add_column.

class AddTimestampsToUsers < ActiveRecord::Migration
  def change
    add_timestamps(:users, null: false)
  end
end

Answer 2

A lot of answers here, but I'll post mine too because none of the previous ones really worked for me :)

As some have noted, #add_timestamps unfortunately adds the null: false restriction, which will cause old rows to be invalid because they don't have these values populated. Most answers here suggest that we set some default value (Time.zone.now), but I wouldn't like to do that because these default timestamps for old data will not be correct. I don't see the value in adding incorrect data to the table.

So my migration was simply:

class AddTimestampsToUser < ActiveRecord::Migration
  def change_table
    add_column :projects, :created_at, :datetime
    add_column :projects, :updated_at, :datetime
  end
end

No null: false, no other restrictions. Old rows will continue being valid with created_at as NULL, and update_at as NULL (until some update is performed to the row). New rows will have created_at and updated_at populated as expected.

Answer 3

I ran into the same issue on Rails 5 trying to use

change_table :my_table do |t|
    t.timestamps
end

I was able to add the timestamp columns manually with the following:

change_table :my_table do |t|
    t.datetime :created_at, null: false, default: DateTime.now
    t.datetime :updated_at, null: false, default: DateTime.now
end

Answer 4

It's change, not change_table for Rails 4.2:

class AddTimestampsToUsers < ActiveRecord::Migration
  def change
    add_timestamps(:users)
  end
end

Answer 5

The issue with most of the answers here is that if you default to Time.zone.now all records will have the time that the migration was run as their default time, which is probably not what you want. In rails 5 you can instead use now(). This will set the timestamps for existing records as the time the migration was run, and as the start time of the commit transaction for newly inserted records.

class AddTimestampsToUsers < ActiveRecord::Migration def change add_timestamps :users, default: -> { 'now()' }, null: false end end

Answer 6

def change
  add_timestamps :table_name
end