On Fri, Oct 13, 2023 at 6:18 PM Andrei Lepikhov <a.lepik...@postgrespro.ru> wrote:
> On 23/8/2023 12:37, Richard Guo wrote: > > To fix it we may need to modify RelOptInfos for Path, BitmapHeapPath, > > ForeignPath and CustomPath, and modify IndexOptInfos for IndexPath. It > > seems that that is not easily done without postponing reparameterization > > of paths until createplan.c. > > > > Attached is a patch which is v5 + fix for this new issue. > > Having looked into the patch for a while, I couldn't answer to myself > for some stupid questions: Thanks for reviewing this patch! I think these are great questions. > 1. If we postpone parameterization until the plan creation, why do we > still copy the path node in the FLAT_COPY_PATH macros? Do we really need > it? Good point. The NestPath's origin inner path should not be referenced any more after the reparameterization, so it seems safe to adjust the path itself, without the need of a flat-copy. I've done that in v8 patch. > 2. I see big switches on path nodes. May it be time to create a > path_walker function? I recall some thread where such a suggestion was > declined, but I don't remember why. I'm not sure. But this seems a separate topic, so maybe it's better to discuss it separately? > 3. Clause changing is postponed. Why does it not influence the > calc_joinrel_size_estimate? We will use statistics on the parent table > here. Am I wrong? Hmm, I think the reparameterization does not change the estimated size/costs. Quoting the comment * The cost, number of rows, width and parallel path properties depend upon * path->parent, which does not change during the translation. Hi Tom, I'm wondering if you've had a chance to follow this issue. What do you think about the proposed patch? Thanks Richard
v8-0001-Postpone-reparameterization-of-paths-until-when-creating-plans.patch
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