ruby on rails - How to set a default value for a datetime column to record creation time in a migration?

Question

Consider the table creation script below:

create_table :foo do |t|
  t.datetime :starts_at, :null => false
end

Is it's possible to set the default value as the current time?

I am trying to find a DB independent equivalent in rails for the SQL column definitions given below:

Oracle Syntax

start_at DATE DEFAULT SYSDATE() 

MySQL Syntax

start_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP

OR

start_at DATETIME DEFAULT NOW()

Answer 1

This is supported now in Rails 5.

Here is a sample migration:

class CreatePosts < ActiveRecord::Migration[5.0]
  def change
    create_table :posts do |t|
      t.datetime :modified_at, default: -> { 'CURRENT_TIMESTAMP' }
      t.timestamps
    end
  end 
end

See discussion at https://github.com/rails/rails/issues/27077 and answer there by prathamesh-sonpatki