DZone Snippets: migration code

Converting Mysql Tables in InnoDB

Mickael (Mickael) — Thu, 19 Jul 2007 12:43:43 GMT

// description of your code here



class ConvertMysqlToInnodb < ActiveRecord::Migration

 def self.up

   config = ActiveRecord::Base.configurations

   begin

     STDERR.puts "Migrating all existing tables to InnoDB"

     schema = []

     select_all('SHOW TABLES').inject([]) do |schema, table|

       schema << "ALTER TABLE #{table.to_a.first.last} ENGINE=InnoDB"

     end

     schema.each { |line| execute line }

   end if config[RAILS_ENV]['adapter'] == 'mysql' unless $schema_generator

 end

source http://trac.typosphere.org/browser/trunk/db/migrate/015_convert_mysql_to_innodb.rb



 def self.down

   # don't do anything

   # this is a one-way migration, but it's not "irreversable"

   # because it doesn't change any code logic

 end

end

rails generator syntax

ovhaag (Oliver Haag) — Sun, 08 Oct 2006 18:52:22 GMT

// generate application



rails projectname

// generate migration.



ruby script/generate migration migration_name

ruby script/generate migration add_price

// generate model
// we can give a list of columns and types
// :string, :text, :integer, :decimal, :float, :date, ...



ruby script/generate model model_name

ruby script/generate model user name:string hashed_password:string salt:string

// generate controller



ruby script/generate controller controller_name method_name(s)

ruby script/generate controller store index

// generate scaffold



ruby script/generate scaffold model_name controller_name

ruby script/generate scaffold product admin

tip: recover from failed rails 'down' migration

MattScilipoti (Matt Scilipoti) — Sun, 26 Mar 2006 02:53:55 GMT

From: http://jamis.jamisbuck.org/articles/2005/12/14/two-tips-for-working-with-databases-in-rails

The second tip is handy when you’re working on a migration. I find that the process (for me) works like this:

* Create the migration and run it.
* Discover I forgot something.
* Migrate down to the previous schema version.
* Change the migration and run it again.

(Repeat as necessary.) However, being the imperfect programmer that I am, I find that I often implement the #down method incorrectly, forgetting to drop a table or remove a column. Thus, when I try to run the migration again, it fails saying that the table/column already exists.

Using script/console and ActiveRecord::Schema, it becomes a cinch to clean up the artifacts:



ActiveRecord::Schema.define do

    drop_table :foos

    remove_column :bars, :blitz

    remove_column :bars, :things

  end