coredump of 9.3.2

Hi!

Rather simple script (original query was a 500 lines of SQL with >100 Mb of
gzipped dump. Query is looked strange, but actually it was auto-generated):

CREATE TABLE t (a int, b int);
CREATE TABLE tt (c int);

INSERT INTO t VALUES (1,1), (2,2);
INSERT INTO tt VALUES (2);

SELECT
*
FROM
t
WHERE (
CASE
WHEN a%2 IN (SELECT c FROM tt) THEN a
END IN (SELECT c FROM tt)
);

I suppose, the problem is connected to hashed subplan, but I'm not very familiar
with executor. And this affects all supported versions of pgsql.

--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/

On 12/10/2013 09:39 AM, Teodor Sigaev wrote:
>
> SELECT
> *
> FROM
> t
> WHERE (
> CASE
> WHEN a%2 IN (SELECT c FROM tt) THEN a
> END IN (SELECT c FROM tt)
> );

Wow, it wouldn't have occured to me that that was even supported syntax.
I'm not suprised that it doesn't work ...

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

Teodor Sigaev <teodor(at)sigaev(dot)ru> writes:
> SELECT
> *
> FROM
> t
> WHERE (
> CASE
> WHEN a%2 IN (SELECT c FROM tt) THEN a
> END IN (SELECT c FROM tt)
> );

> I suppose, the problem is connected to hashed subplan, but I'm not very familiar
> with executor. And this affects all supported versions of pgsql.

It seems to be a planner bug: it's doing the wrong thing with the
PARAM_SUBLINK Params for the nested IN SubLinks. (They don't look
to be nested textually, but they are, and convert_testexpr is
mistakenly replacing the inner one's Params when it should only
be replacing the outer one's Params.)

I think this has probably been broken since about 2005 :-(.
The comment on convert_testexpr claims it doesn't need to worry
about nested cases; which is true when it's called during
SS_process_sublinks, but not so much when it's called from
convert_ANY_sublink_to_join. Some digging in the git history
suggests that the latter call existed at the time, meaning the
comment was wrong even when written.

regards, tom lane