extract_value_from_default

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 134
        def self.extract_value_from_default(default)
          case default
            # This is a performance optimization for Ruby 1.9.2 in development.
            # If the value is nil, we return nil straight away without checking
            # the regular expressions. If we check each regular expression,
            # Regexp#=== will call NilClass#to_str, which will trigger
            # method_missing (defined by whiny nil in ActiveSupport) which
            # makes this method very very slow.
            when NilClass
              nil
            # Numeric types
            when /\A\(?(-?\d+(\.\d*)?\)?)\z/
              $1
            # Character types
            when /\A\(?'(.*)'::.*\b(?:character varying|bpchar|text)\z/
              $1
            # Binary data types
            when /\A'(.*)'::bytea\z/
              $1
            # Date/time types
            when /\A'(.+)'::(?:time(?:stamp)? with(?:out)? time zone|date)\z/
              $1
            when /\A'(.*)'::interval\z/
              $1
            # Boolean type
            when 'true'
              true
            when 'false'
              false
            # Geometric types
            when /\A'(.*)'::(?:point|line|lseg|box|"?path"?|polygon|circle)\z/
              $1
            # Network address types
            when /\A'(.*)'::(?:cidr|inet|macaddr)\z/
              $1
            # Bit string types
            when /\AB'(.*)'::"?bit(?: varying)?"?\z/
              $1
            # XML type
            when /\A'(.*)'::xml\z/
              $1
            # Arrays
            when /\A'(.*)'::"?\D+"?\[\]\z/
              $1
            # Object identifier types
            when /\A-?\d+\z/
              $1
            else
              # Anything else is blank, some user type, or some function
              # and we can't know the value of that, so return nil.
              nil
          end
        end