class ActiveRecord::ConnectionAdapters::MysqlColumn

def extract_default(default)
  if sql_type =~ /blob/i || type == :text
    if default.blank?
      return null ? nil : ''
    else
      raise ArgumentError, "#{type} columns cannot have a default value: #{default.inspect}"
    end
  elsif missing_default_forged_as_empty_string?(default)
    nil
  else
    super
  end
end

def extract_limit(sql_type)
  case sql_type
  when /blob|text/i
    case sql_type
    when /tiny/i
      255
    when /medium/i
      16777215
    when /long/i
      2147483647 # mysql only allows 2^31-1, not 2^32-1, somewhat inconsistently with the tiny/medium/normal cases
    else
      super # we could return 65535 here, but we leave it undecorated by default
    end
  when /^bigint/i;    8
  when /^int/i;       4
  when /^mediumint/i; 3
  when /^smallint/i;  2
  when /^tinyint/i;   1
  else
    super
  end
end

def has_default?
  return false if sql_type =~ /blob/i || type == :text #mysql forbids defaults on blob and text columns
  super
end

def missing_default_forged_as_empty_string?(default)
  type != :string && !null && default == ''
end

def simplified_type(field_type)
  return :boolean if MysqlAdapter.emulate_booleans && field_type.downcase.index("tinyint(1)")
  return :string  if field_type =~ /enum/i
  super
end