From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
---|---|
To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
Cc: | Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: BRIN minmax multi - incorrect distance for infinite timestamp/date |
Date: | 2023-10-18 10:13:48 |
Message-ID: | CAEZATCXSG0=NK67AhhED+25qXRAJDJqSGPOUY1zdopurTc+QjA@mail.gmail.com |
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On Tue, 17 Oct 2023 at 21:25, Tomas Vondra
<tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
>
> Here's a couple cleaned-up patches fixing the various discussed here.
> I've tried to always add a regression test demonstrating the issue
> first, and then fix it in the next patch.
>
This looks good to me.
> 2) incorrect subtraction in distance for date values (0003)
>
> All the problems except "2" have been discussed earlier, but this seems
> a bit more serious than the other issues, as it's easier to hit. It
> subtracts the values in the opposite order (smaller - larger), so the
> distances are negated. Which means we actually merge the values from the
> most distant ones, and thus are "guaranteed" to build very a very
> inefficient summary.
>
Yeah, that's not good. Amusingly this accidentally made infinite dates
behave correctly, since they were distance 0 away from anything else,
which was larger than all the other negative distances! But yes, that
needed fixing properly.
Thanks for taking care of this.
Regards,
Dean
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