Whenever you create a table from a database migration, remember to add updated_at and created_at timestamps to that table. Without those timestamps, investigating future bug reports will be hell. Always have timestamps.
Adding timestamps to new tables
When you create a table using create_table, you can add timestamps by using the timestamps shortcut:
class CreateEpisode < ActiveRecord::Migration
def change
create_table :episodes do |t|
t.string :name
t.timestamps
end
end
end
ActiveRecord will automagically set those timestamps when you create or update a record.
Adding timestamps to existing tables
If you forgot to add timestamps in the past, take a look at your db/schema.rb and add timetamps for any table that is missing them. You can use the add_timestamps macros for that.
Rails >= 4.2
Since Rails 4.2 add_timestamps also adds a NOT NULL constraint by default. So you will see an error like "ERROR: column "created_at" contains null values" when you don't take care of it. Here are two approaches on how to handle this:
(a) Don't have a NOT NULL constraint:
class AddMissingTimestamps < ActiveRecord::Migration
def change
add_timestamps :shows, null: true
add_timestamps :tags, null: true
add_timestamps :users, null: true
end
end
(b) Fill the datetimes with an old time (to mark it as being backfilled):
class AddMissingTimestamps < ActiveRecord::Migration
def change
# Add timestamps column, but without a NOT NULL constraint
add_timestamps :shows, null: true
# Backfill missing data with a really old date
time = Time.zone.parse('2000-01-01 00:00:00')
update "UPDATE shows SET created_at = '#{time}'"
update "UPDATE shows SET updated_at = '#{time}'"
# Restore NOT NULL constraints to be in line with the Rails default
change_column_null :shows, :created_at, false
change_column_null :shows, :updated_at, false
# ...
end
end
Rails < 4.2
class AddMissingTimestamps < ActiveRecord::Migration
def change
add_timestamps :shows
add_timestamps :tags
add_timestamps :users
end
end
Also
Always have timestamps.
