[Nitro] Storing binary data

[Michael Neumann]

Am Tuesday 14 June 2005 13:29 schrieb George Moschovitis:
> Hello Michael
>
> when recoding the psql driver I forgot to overide the default mapping to a
> blob column that was included in earlier versions of the Og-Psql adapter.
> The prefered way is BYTEA, and this will be fixed in the imminent 0.19.0
> release of Og.

Here's my patch/override to enable BYTEA's:

class Og::Binary; end # tag for binary properties

require 'og/adapters/psql'
class Og::PsqlAdapter

  class << self
    #
    # Encodes a string as bytea value.
    #
    # for encoding rules see:
    #   http://www.postgresql.org/docs/7.4/static/datatype-binary.html
    #

    def encode_bytea(str)
      str.gsub(/[\000-\037\047\134\177-\377]/) {|b| 
"\\#{ b[0].to_s(8).rjust(3, '0') }" }
    end

    #
    # Decodes a bytea encoded string.
    #
    # for decoding rules see:
    #   http://www.postgresql.org/docs/7.4/static/datatype-binary.html
    #
    def decode_bytea(str)
      str.gsub(/\\(\\|'|[0-3][0-7][0-7])/) {|s|
        if s.size == 2 then s[1,1] else s[1,3].oct.chr end
      }
    end
  end

  alias __old_read_prop read_prop
  alias __old_write_prop write_prop

  def read_prop(p, idx)
    if p.klass.ancestors.include?(Og::Binary)
      return "#{ self.class }.decode_bytea(res.getvalue(tuple, #{idx}))"
    else
      __old_read_prop(p, idx)
    end
  end

  def write_prop(p)
    if p.klass.ancestors.include?(Og::Binary)
      return %|#\{@#{p.symbol} ? 
"'#\{#{self.class}.escape(#{self.class}.encode_bytea(@#{p.symbol}))\}'" : 
'NULL'\}|
    else
      __old_write_prop(p)
    end
  end
end


> Do you think than BLOB is better than BYTEA?

Blobs are actually a lot faster (and uses up less storage) for large data I 
think, as they need not to be encoded and decoded. I'd like to have both ;-) 
BYTEA is easier to handle than BLOBs, but if you implement BLOBs in a way 
that they are transparent to the user (as I did in Ruby/DBI), I'd prefer that 
way.

Regards,

  Michael