Re: Caching query plan costs

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).

Greetings,

Andres Freund