empty concatenate

Hi,
I try concatenate text via standard '||' oprerator, but result is
interesting:  

PgSQL 6.5.3/7.0:
~~~~~~~~~~~~~~~
test=> select * from x;
a  |b
---+---
AAA|BBB
xxx|
(2 rows)

test=> select a || b from x;
?column?
--------
AAABBB                                 <-------------- empty !
(2 rows)


Oracle8:
~~~~~~~~
SVRMGR> select * from x;
A                                B
-------------------------------- --------------------------------
AAA                              BBB
xxx
2 rows selected.
SVRMGR> select a || b from x;
A||B
----------------------------------------------------------------
AAABBB
xxx                                <---------------- not empty !
2 rows selected.


I fistly think that problem is in the textcat() routine, but PgSQL ignore 
all functions's results if any argument (column) is empty. Example:

text *
xxx(text *t1, text *t2)
{       text       *result;
       result = (text *) palloc(10 + VARHDRSZ);       strcpy(VARDATA(result), "happy");       VARSIZE(result) = 5 +
VARHDRSZ;      elog(NOTICE, "RETURN: %s", VARDATA(result));
 
       return result;                         /* always return 'happy' */
} 
test=> select * from x;
a  |b
---+---
AAA|BBB
xxx|
(2 rows)

test=> select  xxx(a, b) from x;
NOTICE:  RETURN: happy
NOTICE:  RETURN: happy
xxx
----
happy                                           <--------- empty ?!
(2 rows)


Why is it empty? I believe that is not feature :-)
                    Karel

PS. sorry, if this is old point, mail-list archive seacher (htdig)    not work...

----------------------------------------------------------------------
Karel Zak <zakkr@zf.jcu.cz>              http://home.zf.jcu.cz/~zakkr/

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