| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Alena Rybakina <lena(dot)ribackina(at)yandex(dot)ru> |
| Cc: | "Finnerty, Jim" <jfinnert(at)amazon(dot)com>, Marcos Pegoraro <marcos(at)f10(dot)com(dot)br>, Alena Rybakina <a(dot)rybakina(at)postgrespro(dot)ru>, Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>, pgsql-hackers(at)postgresql(dot)org, teodor(at)sigaev(dot)ru, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
| Subject: | Re: POC, WIP: OR-clause support for indexes |
| Date: | 2023-08-06 21:43:08 |
| Message-ID: | CAH2-Wzk4wZvMNKo8JoY6KNvo1eeCQtErse+72UoCG5Lj8C8Vmg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Aug 5, 2023 at 7:01 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Of course this immediately makes me wonder: shouldn't your patch be
> able to perform an additional transformation here? You know, by
> transforming "a.x = 42 OR a.x = 44" into "a IN (42, 44)"? Although I
> haven't checked for myself, I assume that this doesn't happen right
> now, since your patch currently performs all of its transformations
> during parsing.
Many interesting cases won't get SAOP transformation from the patch,
simply because of the or_transform_limit GUC's default of 500. I don't
think that that design makes too much sense. It made more sense back
when the focus was on expression evaluation overhead. But that's only
one of the benefits that we now expect from the patch, right? So it
seems like something that should be revisited soon.
I'm not suggesting that there is no need for some kind of limit. But
it seems like a set of heuristics might be a better approach. Although
I would like to get a better sense of the costs of the transformation
to be able to say too much more.
--
Peter Geoghegan
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