On Mon, Sep 3, 2018 at 02:53:59PM -0700, Andres Freund wrote:
> On 2018-09-03 14:56:28 -0400, Bruce Momjian wrote:
> > On Mon, Sep 3, 2018 at 11:42:31AM -0700, Andres Freund wrote:
> > > > and JIT, so it doesn't have to be 100% accurate.
> > >
> > > JIT decision is done after main planning, so we know the cost.
> >
> > Well, as I remember, we are considering disabling JIT in PG 11 because
> > of the use of fixed costs to trigger it. Could executor information
> > help decide to use JIT?
>
> I don't think so. The issues with JIT planning are more that it's
> costing is simplistic (for good-ish reason, to avoid increasing the
> number of plans), and that there's no caching (lots of infrastructure
> work needed).
Uh, yeah, that was my question. If we knew the cost was high before we
plan, could we realistically increase the number of plans to avoid the
cost-trigger issue?
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
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