Horton

Re: BRIN minmax multi - incorrect distance for infinite timestamp/date

Dean Rasheed <dean.a.rasheed@gmail.com>

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From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-10-19T07:04:44Z
Lists: pgsql-hackers 
On Thu, 19 Oct 2023, 05:32 Ashutosh Bapat, <ashutosh.bapat.oss@gmail.com>
wrote:

> On Wed, Oct 18, 2023 at 8:23 PM Tomas Vondra
> <tomas.vondra@enterprisedb.com> wrote:
>
> >
> > I did use that many values to actually force "compaction" and merging of
> > points into ranges. We only keep 32 values per page range, so with 2
> > values we'll not build a range. You're right it may still trigger the
> > overflow (we probably still calculate distances, I didn't realize that),
> > but without the compaction we can't check the query plans.
> >
> > However, I agree 60 values may be a bit too much. And I realized we can
> > reduce the count quite a bit by using the values_per_range option. We
> > could set it to 8 (which is the minimum).
> >
>
> I haven't read BRIN code, except the comments in the beginning of the
> file. From what you describe it seems we will store first 32 values as
> is, but later as the number of values grow create ranges from those?
> Please point me to the relevant source code/documentation. Anyway, if
> we can reduce the number of rows we insert, that will be good.
>

I don't think 60 values is excessive, but instead of listing them out by
hand, perhaps use generate_series().

Regards,
Dean

Commits

  1. Fix minmax-multi distance for extreme interval values

  2. Fix minmax-multi on infinite date/timestamp values

  3. Fix calculation in brin_minmax_multi_distance_date

  4. Fix overflow when calculating timestamp distance in BRIN