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

On Thu, Dec 10, 2015 at 4:55 AM, Andreas Seltenreich <seltenreich(at)gmx(dot)de> wrote:
> Tom Lane writes:
>
>> Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
>>> Aside from the functional issues, could your changes result in
>>> performance regressions?
> [...]
>> It's a little bit harder to gauge the impact on planner speed. The
>> transitive closure calculation could be expensive in a query with many
>> lateral references, but that doesn't seem likely to be common; and anyway
>> we'll buy back some of that cost due to simpler tests later. I'm
>> optimistic that we'll come out ahead in HEAD/9.5 after the removal
>> of LateralJoinInfo setup. It might be roughly a wash in the back
>> branches.
>
> On the empirical side: I see a speedup of 0.4% in testing speed with the
> patch applied. It could very well be me venting the room one additional
> time during the second session, resulting in the CPUs spending more time
> in their opportunistic frequency range or something.

Really...wow. That satisfies me. You ought to be commended for
sqlsmith -- great stuff.

merlin