Re: WIP: BRIN multi-range indexes

Hi,
bq. Not sure why would that be an issue

Moving the (start > end) check is up to your discretion.

But the midpoint computation should follow text book :-)

Cheers

On Wed, Feb 3, 2021 at 4:59 PM Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
wrote:

>
>
> On 2/4/21 1:49 AM, Zhihong Yu wrote:
> > Hi,
> > For 0007-Remove-the-special-batch-mode-use-a-larger--20210203.patch :
> >
> > + /* same as preceding value, so store it */
> > + if (compare_values(&range->values[start + i - 1],
> > + &range->values[start + i],
> > + (void *) &cxt) == 0)
> > + continue;
> > +
> > + range->values[start + n] = range->values[start + i];
> >
> > It seems the comment doesn't match the code: the value is stored when
> > subsequent value is different from the previous.
> >
>
> Yeah, you're right the comment is wrong - the code is doing exactly the
> opposite. I'll need to go through this more carefully.
>
> > For has_matching_range():
> > + int midpoint = (start + end) / 2;
> >
> > I think the standard notion for midpoint is start + (end-start)/2.
> >
> > + /* this means we ran out of ranges in the last step */
> > + if (start > end)
> > + return false;
> >
> > It seems the above should be ahead of computation of midpoint.
> >
>
> Not sure why would that be an issue, as we're not using the value and
> the values are just plain integers (so no overflows ...).
>
>
> regards
>
> --
> Tomas Vondra
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>