Re: 9.1rc1: TRAP: FailedAssertion("!(item_width > 0)", File: "costsize.c", Line: 3274)

On Mon, Aug 22, 2011 at 4:16 PM, Erik Rijkers <er(at)xs4all(dot)nl> wrote:
> I am developing against 9.1beta3 and encountered this problem. I repeated it against rc1 (or
> actually, REL9_1_STABLE taken from git today).
>
> The below SQL causes:
>
> TRAP: FailedAssertion("!(item_width > 0)", File: "costsize.c", Line: 3274)
>
> and the session crashes.
>
> select *
> from (
>  select
>       col1
>    ,  col2
>    ,  reviewed
>  from
>    (values
>        ( 1111, 'aweyu', 3)
>      , ( 2222, 'bwetu', 2)
>      , ( 3333, 'vwxyz', 1)
>     )
>        as r(col1,col2,col3)
>  left join (
>                select 1 as reviewed, c2 from ( values ('abcde') ) as t1(c2)
>      union all select 0 as reviewed, c2 from ( values ('vwxyz') ) as t2(c2)
>  )
>     as up_all on up_all.c2 = r.col2
>  order by col3
> )
>  as f
> ;
>
>
> To simplify I used 'values' for the actual tables that I am using, but the above still causes the
> FailedAssertion.
>
> Removing the outer select avoids the error and
> removing order by avoids the error

I can reproduce this on master but not on 9.0. I suspect the problem
was introduced by this commit:

commit 0f61d4dd1b4f95832dcd81c9688dac56fd6b5687
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Date: Fri Nov 19 17:31:50 2010 -0500

Improve relation width estimation for subqueries.

...but I haven't confirmed that yet.

--
Robert Haas
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