Content-Type: text/plain;
  charset="us-ascii"
From: sad <sad@bankir.ru>
Organization: IT
To: "psql" <pgsql-sql@postgresql.org>
Subject: unescaped output of bytea
Date: Thu, 30 Oct 2003 09:31:54 +0000
User-Agent: KMail/1.4.3
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Message-Id: <200310300931.54585.sad@bankir.ru>

Good day Guru

I thought on output to input relation in general.

Manual says about scalar types that input and output functions should be=20
inverse to each other, because of dump problems (if output function prints
a value not in a format that input function waiting for)

That's the geat problem i thought. If so then an external representation=20
could not be deffer of  SQL-constant representation (clear?)
Very common problem it is.
Most fields in this case should be manually (application level) transformed
both directions.

Then I try the experiment with text constant and text field dump:

INSERT INTO ttt values ('a\\b\'c''');
SELECT * FROM ttt;
  fff
--------
 a\b'c'

I see the output not inverse to the input.
then I DUMP the table ttt and see into the dump file:

INSERT INTO ttt VALUES ('a\\b\'c''');

THAT'S IT !!! Dump DIFFERS to plain output !
the same result with escaping apostroph we could see in bytea type.

this GOOD, VERY GOOD fact allows us to have unescaped output of bytea=20
without problems with a dump.