Dirk.Net

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.