Re: [sqlsmith] Failed to generate plan on lateral subqueries

On Tue, Dec 08, 2015 at 12:13:41PM -0500, Tom Lane wrote:
> Andreas Seltenreich <seltenreich@gmx.de> writes:
> >> I no longer see "failed to build any n-way joins" after pulling,
> >> but there are still instances of "could not devise a query plan".
> >> Samples below.
> 
> > sorry, I spoke too soon: nine of the former have been logged
> > through the night.  I'm attaching a larger set of sample queries
> > this time in case that there are still multiple causes for the
> > observed errors.
> 
> Hm.  At least in the first of these cases, the problem is that the
> code I committed yesterday doesn't account for indirect lateral
> dependencies.  That is, if S1 depends on S2 which depends on the
> inner side of an outer join, it now knows not to join S2 directly to
> the outer side of the outer join, but it doesn't realize that the
> same must apply to S1.
> 
> Maybe we should redefine lateral_relids as the transitive closure of
> a rel's lateral dependencies?  Not sure.

That seems like it would fix the problem once and for good.  Is there
any reason to believe that the lateral dependencies could go in a
loop, i.e. is there a reason to put in checks for same in the
transitive closure construction?

Cheers,
David.
-- 
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com

Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate