Note:

BIT MySQL data type was added in MySQL 5.0.3 for MyISAM, and extended in 5.0.5 to MEMORY, InnoDB, BDB, and NDBCLUSTER. Before 5.0.3, BIT is a synonym for TINYINT(1).

Config:

os: Windows XP
rails: 2.3.8
ruby: 1.8.7
gem mysql: 2.8.1
mysql server: 5.0.41

Problem

Activerecord#column_name? return false instead of true when using datatype "bit(1)" with mysql and the value in the database is 1 (true).

To support the bit data type, I have changed the following files:

/active_record/connection_adapters/abstract/schema_definitions.rb

def value_to_boolean(value)
  if value.is_a?(String) && value.blank?
    nil
  else
+++   value = value.ord if value.is_a?(String) && value.ord < 2 # Support bit(1) mysql datatype for bool
    TRUE_VALUES.include?(value)
  end
end

/active_record/connection_adapters/mysql_adapter.rb

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

  def extract_limit(sql_type)
    case sql_type
    when /blob|text/i
      case sql_type
      when /tiny/i
         255
 ...
    when /^tinyint/i;   1
+++    when /^bit/i;   1
    else
      super
    end
  end

Best regards,