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(at)zf(dot)jcu(dot)cz> http://home.zf.jcu.cz/~zakkr/

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