Re: [sqlsmith] Crash in apply_projection_to_path
| От | Amit Kapila |
|---|---|
| Тема | Re: [sqlsmith] Crash in apply_projection_to_path |
| Дата | |
| Msg-id | CAA4eK1J-JtJi9dZ+iCFp813OyOWMMtY-eT0HmFdYznn=AFm5YA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [sqlsmith] Crash in apply_projection_to_path (Robert Haas <robertmhaas@gmail.com>) |
| Ответы |
Re: [sqlsmith] Crash in apply_projection_to_path
|
| Список | pgsql-hackers |
On Fri, Apr 29, 2016 at 8:07 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Thu, Apr 28, 2016 at 10:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Andreas Seltenreich <seltenreich@gmx.de> writes:
> >> the following query against the regression database crashes master as of
> >> 23b09e15.
> >
> >> select 1 from depth0 inner join depth1 on (depth0.c = depth1.c)
> >> where depth0.c @@ depth1.c limit 1;
> >
> > What's going on here is that add_partial_path is recycling a now-dominated
> > partial path without regard for the fact that there's already a GatherPath
> > pointing at that old partial path. Later use of the GatherPath tries to
> > make use of its now-dangling subpath pointer.
> >
> > I'd be inclined to think that it's silly to build GatherPaths in advance
> > of having finalized the list of partial paths for a rel.
>
> Uh ... yeah, that shouldn't be happening. I obviously screwed something up.
>
What's happening here is that to form joinrel, we need to call add_paths_to_joinrel() with both outer and inner relation twice, once with rel1 as outer relation and rel1 as inner relation and vice versa. So now the second call to add_paths_to_joinrel() can replace a partial path which is being referenced by GatherPath generated in first call. I think we should generate gather paths for join rel after both the calls to add_paths_to_joinrel() aka in make_join_rel(). Attached patch on above lines fixes the problem for me.
>
> On Thu, Apr 28, 2016 at 10:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Andreas Seltenreich <seltenreich@gmx.de> writes:
> >> the following query against the regression database crashes master as of
> >> 23b09e15.
> >
> >> select 1 from depth0 inner join depth1 on (depth0.c = depth1.c)
> >> where depth0.c @@ depth1.c limit 1;
> >
> > What's going on here is that add_partial_path is recycling a now-dominated
> > partial path without regard for the fact that there's already a GatherPath
> > pointing at that old partial path. Later use of the GatherPath tries to
> > make use of its now-dangling subpath pointer.
> >
> > I'd be inclined to think that it's silly to build GatherPaths in advance
> > of having finalized the list of partial paths for a rel.
>
> Uh ... yeah, that shouldn't be happening. I obviously screwed something up.
>
What's happening here is that to form joinrel, we need to call add_paths_to_joinrel() with both outer and inner relation twice, once with rel1 as outer relation and rel1 as inner relation and vice versa. So now the second call to add_paths_to_joinrel() can replace a partial path which is being referenced by GatherPath generated in first call. I think we should generate gather paths for join rel after both the calls to add_paths_to_joinrel() aka in make_join_rel(). Attached patch on above lines fixes the problem for me.
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