create_table with unique combo

I need to create a table replacing default integer id with a string id
and making a combo of (id and version) unique primary key. Here is
what I've got so far.

class CreateCatalogs < ActiveRecord::Migration
  def self.up
    create_table :catalogs, :id => false do |t|
      t.string :id, :limit => 20, :null => false
      t.string :version, :default => '01'


  def self.down
    drop_table :catalogs

hi slave,you can do it use the connection method of migration
use it like ActiveRecord::Base.connection_pool.checkout

alternatively if i leave default integer id as primary key I need to
make sure combo of name and version are unique.

    create_table :catalogs do |t|
      t.string :name
      t.string :version, :default => '01'

To ensure uniqueness, you can add an index

add_index :catalogs, [:name, :version], :unique => true

Andrew Timberlake

"I have never let my schooling interfere with my education" - Mark Twain

on the same subject..
I need to ensure uniqness of name in a table. I tried setting collumn
to unique (see below) but that did not work. I still can create
records with same name field.

   create_table :properties do |t|
      t.string :name, :unique => true
      t.string :description