Re: BUG #18806: When enable_rartitionwise_join is set to ON, the database shuts down abnormally

Amit Langote <amitlangote09(at)gmail(dot)com> 于2025年2月13日周四 10:39写道：

> Hi Richard,
>
> On Wed, Feb 12, 2025 at 11:30 PM Richard Guo <guofenglinux(at)gmail(dot)com>
> wrote:
> > On Wed, Feb 12, 2025 at 10:04 PM Ashutosh Bapat
> > <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
> > > Hmm. The code there assumes that all the Relids will at least have one
> > > parent each of the children involved. For some reason
> > > sjinfo->min_lefthand has only relid 1 but not 2 or 5. 2 and 5 are
> > > actually the parent relids of the children passed in respectively. The
> > > join is between 2 and 5, then why is 1 appearing in the min_lefthand.
> > > It might be legitimate, but we need to find the reason. If it's
> > > legitimate, I think we need to copy the Relids which haven't undergone
> > > any translation so as to keep them isolated from the parent relids.
> >
> > Yes, it's legitimate. For the semijoin, its join clause only
> > references {1} and {5}, with no other ordering restrictions.
> > Therefore, the minimum LHS for this join consists only of {1}.
> >
> > Instead of copying the untranslated Relids and freeing them later, I
> > think it might be better to modify free_child_join_sjinfo() to avoid
> > freeing the untranslated members of child_sjinfo.
>
> free_child_join_sjinfo() frees min_lefthand and other fields
> initialized by build_child_join_sjinfo(), assuming that
> adjust_child_relids() creates a copy. However, this does not always
> seem to be the case, as demonstrated in this report.
>
> I'm wondering if the following line in adjust_child_relids() should be
> using bms_copy() instead:
>
> /* Otherwise, return the original set without modification. */
> return relids;
> }
>

This fix is ok for me. Keeping the child's info isolated from the parents
seems safer.

--
Thanks,
Tender Wang