Message-ID: <5130BBE7.3030201@archonet.com>
Date: Fri, 01 Mar 2013 14:32:07 +0000
From: Richard Huxton <dev@archonet.com>
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To: Marko Rihtar <rihtar.marko@gmail.com>
CC: pgsql-sql@postgresql.org
Subject: Re: Concatenating bytea types...
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On 28/02/13 10:21, Marko Rihtar wrote:
> Hi all,
>
> i have a little problem.
> I'm trying to rewrite one procedure from mysql that involves bytes
> concatenation.
> This is my snippet from postgres code:

You seem to be mixing up escape and hex literal formatting along with 
decode(). The following should help.

BEGIN;

CREATE FUNCTION to_hex_pair(int) RETURNS text AS $$
     SELECT right('0' || to_hex($1), 2);
$$ LANGUAGE sql;

CREATE FUNCTION f_concat_bytea1(bytea, bytea) RETURNS text AS $$
BEGIN
     RETURN $1 || $2;
END;
$$ LANGUAGE plpgsql;

CREATE FUNCTION f_concat_bytea2(bytea, bytea) RETURNS bytea AS $$
DECLARE
     cv1 bytea;
BEGIN
     cv1 := '\x01'::bytea;
     RETURN $1 || cv1 || $2;
END;
$$ LANGUAGE plpgsql;

CREATE FUNCTION f_concat_bytea3(text, text) RETURNS bytea AS $$
DECLARE
     cv1 text;
BEGIN
     cv1 := '01';
     RETURN decode($1 || cv1 || $2, 'hex');
END;
$$ LANGUAGE plpgsql;

SELECT '\x000b'::bytea             AS want_this,
        decode('000b','hex')        AS or_this1,
        decode('\000\013','escape') AS or_this2;
SELECT f_concat_bytea1('\x00', '\x0b');
SELECT f_concat_bytea2('\x00', '\x0b');
SELECT f_concat_bytea3('00', '0b');

ROLLBACK;


-- 
   Richard Huxton
   Archonet Ltd


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