Rails Migration to Convert all Table Names and Column Names to underscore

This may be useful for legacy database, whose table and column names are in CamelCase. Use with extreme caution:

class ChangeAllColumnsToUnderscore < ActiveRecord::Migration
include ActiveRecord::ConnectionAdapters::SchemaStatements
require 'active_record/connection_adapters/abstract_adapter'
 
 #not needed in Rails 3
 #pilfered from here:
     #http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-column_exists-3F
	 
def self.column_exists?(table_name, column_name, type = nil, options = {})
 columns(table_name).any?{ |c| c.name == column_name.to_s &&
(!type || c.type == type) &&
(!options[:limit] || c.limit == options[:limit]) &&
(!options[:precision] || c.precision == options[:precision]) &&
(!options[:scale] || c.scale == options[:scale]) }
  end

def self.up
tables.reject {|t| t == "schema_migrations"}.each do |table|
columns(table.to_sym).each do |column|
unless self.column_exists?(table.to_sym, column.name.underscore.to_sym)
rename_column table.to_sym, column.name.to_sym, column.name.underscore.to_sym
end
end

unless table_exists?(table.underscore.to_sym)
rename_table table, table.underscore
end
end
end

def self.down
tables.reject {|t| t == "schema_migrations"}.each do |table|
columns(table.to_sym).each do |column|
unless column_exists?(table.to_sym, column.name.camelize.to_sym)
 rename_column table.to_sym, column.name.to_sym, column.name.camelize.to_sym
end
end

unless table_exists?(table.camelize.to_sym)
rename_table table, table.camelize
end
end
end
end

Hope it helps.

Andreas: "Hope it helps." Yes it does, thank you! Andreas

Posted: 30 August 2011