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How to undo an incorrect rails migration after rake db:migrate

Posted on 2007-11-29
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Last Modified: 2012-08-14
I forgot to put any code in the 'down' section. How do I undo a 'rake db:migrate'?


class User < ActiveRecord::Migration

  def self.up

    create_table :users do |t|

      t.column "username", :string

      t.column "fname", :string

      t.column "lname", :string

      t.column "email", :string

      t.column "hashed_password", :string

      t.column "campus_id", :integer

    end

  end
 

  def self.down

  end

end

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Question by:smetterd
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Wod earned 500 total points
ID: 20376647
http://blog.apesseekingknowledge.net/articles/category/ruby-on-rails

"I kept having typos in my migrations, and it turned out to be easier to just zap all the tables and re-run rake migrate than to undo just enough of the migration to get the db back to the way the migration was expecting.

Anyway, so I wrote this wipedb script that reads database.yml so you don’t need to maintain the database user & password in multiple places."


#! /usr/bin/env ruby

#

# $Id: wipedb 1171 2006-06-10 16:36:57Z jpb $

#

# Copyright 2006 J. P. Block <jpb@ApesSeekingKnowledge.net>
 

require 'ostruct'

require 'optparse'

require 'yaml'
 

class MyArgs

  MODENAMES = %w[development test production]
 

  # return structure showing what opts were picked
 

  def self.parse(args)

    options = OpenStruct.new

    options.mode = 'development'

    options.debug = 0
 

    opts = OptionParser.new do |opts|

      opts.banner = "Usage: script/wipedb [options]" 

      opts.separator "" 

      opts.separator "Specific options:" 

      mode_list = MODENAMES.join(',')

      opts.on("-m MODENAME", "--mode MODENAME", MODENAMES, "Select mode",

                      "  (#{mode_list})") do |the_mode|

        options.mode = the_mode

      end

      opts.on("-d", "--debug", "Turn on debug") do

        options.debug = 1

      end

      opts.on_tail("-h", "--help", "Show this message") do

        puts opts

        exit

      end
 

      opts.on_tail("--version", "Show version") do

        puts "$Id: wipedb 1171 2006-06-10 16:36:57Z jpb $" 

        exit

      end

    end
 

    opts.parse!(args)

    options

  end # parse()

end
 

options = MyArgs.parse(ARGV)
 

mode = options.mode
 

config = YAML.load_file('config/database.yml')
 

database = config[options.mode]['database']

host = config[options.mode]['host']

password = config[options.mode]['password']

username = config[options.mode]['username']
 

if options.debug == 1:  

  puts "mode: #{mode}" 

  puts "database: #{database}" 

  puts "host: #{host}" 

  puts "username: #{username}" 

  puts "password: #{password}" 

end
 

zap_list = `mysqldump -u #{username} -p#{password} --complete-insert --add-drop-table --quick --single-transaction #{database} | grep DROP`
 

zapper = IO.popen("mysql -u #{username} -p#{password} #{database}", "w+")

zap_list.each do |z|

  zapper.puts(z)

end

zapper.close_write

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