Re: BRIN minmax multi - incorrect distance for infinite timestamp/date - Mailing list pgsql-hackers

From Dean Rasheed
Subject Re: BRIN minmax multi - incorrect distance for infinite timestamp/date
Date
Msg-id CAEZATCXSG0=NK67AhhED+25qXRAJDJqSGPOUY1zdopurTc+QjA@mail.gmail.com
Whole thread Raw
In response to Re: BRIN minmax multi - incorrect distance for infinite timestamp/date  (Tomas Vondra <tomas.vondra@enterprisedb.com>)
Responses Re: BRIN minmax multi - incorrect distance for infinite timestamp/date
List pgsql-hackers
On Tue, 17 Oct 2023 at 21:25, Tomas Vondra
<tomas.vondra@enterprisedb.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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