ocaml - How do I return a binary string (bytea) in a PL/Python PostgreSQL routine? -

i'm trying write procedure in pl/python perform conversion of data, return result bytea. (it's quite ugly, actually: marshalling data in ocaml! ugly in python , ocaml @ once; should medal?)

here's looks like:

create or replace function ml_marshal(data varchar) returns bytea $$     import tempfile, os      fn = tempfile.mktemp()     f = open(fn, 'w')      dest_fn = tempfile.mktemp()      f.write("let outch = open_out_bin \"" + dest_fn + "\" in " +             "marshal.to_channel outch (" + data + ") [marshal.no_sharing]; " +             "close_out outch")     f.close()      os.system("ocaml " + fn)     os.unlink(fn)      f = open(dest_fn, 'r')     res = f.read()     f.close()      os.unlink(dest_fn)      return res $$ language plpythonu; 

in short, writes out small ocaml program tempfile creates tempfile data want. read tempfile in, destroy them both, , return result.

only doesn't quite work:

meidi=# select * tblmodel;  modelid |      polies       ---------+------------------        1 | \204\225\246\276        2 | \204\225\246\276 

there 4 bytes in each (there should ~130). if stop unlinking files, becomes obvious why; there 4 non-nul bytes, followed couple of nuls, , appears nuls treated terminators @ stage conversion python postgres!

does know why happens, or how stop it? docs not enlightening.

thanks!

edit: found someone else same problem, solution unsatisfactory.

this fixed release 9.0. had same problem upgraded. release notes:

improve bytea support in pl/python (caleb welton)  bytea values passed pl/python represented binary, rather postgresql bytea text format. bytea values containing null bytes output pl/python. passing of boolean, integer, , float values improved. 

i not think there elegant solution problem in previous postgresql versions.