On Tue, Apr 9, 2024 at 8:55 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > Andrei Lepikhov <a.lepik...@postgrespro.ru> writes: > > On 9/4/2024 09:12, Tom Lane wrote: > >> I have another one that I'm not terribly happy about: > >> Author: Alexander Korotkov <akorot...@postgresql.org> > >> Branch: master [72bd38cc9] 2024-04-08 01:27:52 +0300 > >> Transform OR clauses to ANY expression > > >> * What the medical community would call off-label usage of > >> query jumbling. I'm not sure this is even correct as-used, > >> and for sure it's using that code for something never intended. > >> Nor is the added code adequately (as in, at all) documented. > > > I agree with documentation and disagree with critics on the expression > > jumbling. It was introduced in the core. Why don't we allow it to be > > used to speed up machinery with some hashing? > > I would back up from that a good deal: why do we need to hash here in > the first place? There's no evidence I'm aware of that it's needful > from a performance standpoint.
I think the feature is aimed to deal with large OR lists. I've seen a significant degradation on 10000 or-clause-groups. That might seem like awfully a lot, but actually it's not unachievable in generated queries. Links. 1. https://www.postgresql.org/message-id/CAPpHfduJtO0s9E%3DSHUTzrCD88BH0eik0UNog1_q3XBF2wLmH6g%40mail.gmail.com ------ Regards, Alexander Korotkov
