On 6/18/21 9:54 PM, John Naylor wrote:
On Fri, Jun 18, 2021 at 3:43 PM Tomas Vondra
mailto:tomas.von...@enterprisedb.com>>
wrote:
> Sorry, I'm not sure what you mean by "we set the number of MCVs to the
> number of histograms" :-(
>
> When you say "MCV limit" you mean that we limit the n
On Fri, Jun 18, 2021 at 3:43 PM Tomas Vondra
wrote:
> Sorry, I'm not sure what you mean by "we set the number of MCVs to the
> number of histograms" :-(
>
> When you say "MCV limit" you mean that we limit the number of items to
> statistics target, right? I agree plan time is one concern - but it
On 6/18/21 7:03 PM, John Naylor wrote:
On Wed, Jun 16, 2021 at 8:23 PM Tomas Vondra
mailto:tomas.von...@enterprisedb.com>>
wrote:
> Not really, but to be fair even for the histograms it's only really
> supported by "seems to work in practice" :-(
Hmm, we cite a theoretical result in analyze
On Wed, Jun 16, 2021 at 8:23 PM Tomas Vondra
wrote:
> Not really, but to be fair even for the histograms it's only really
> supported by "seems to work in practice" :-(
Hmm, we cite a theoretical result in analyze.c, but I don't know if there
is something better out there:
* The following choi
On 6/17/21 2:23 AM, Tomas Vondra wrote:
> On 6/17/21 1:31 AM, John Naylor wrote:
>> On Wed, Jun 16, 2021 at 12:23 PM Tomas Vondra
>> mailto:tomas.von...@enterprisedb.com>>
>> wrote:
>>
>> ...
>>
>> + * depth 8 and width 128 is sufficient for relative error ~1.5% with a
>> + * probability of appr
On 6/17/21 1:31 AM, John Naylor wrote:
> On Wed, Jun 16, 2021 at 12:23 PM Tomas Vondra
> mailto:tomas.von...@enterprisedb.com>>
> wrote:
>
> > The attached patch is a very simple (and perhaps naive) implementation
> > adding count-min sketch to pg_statistic for all attributes with a hash
> >
On Wed, Jun 16, 2021 at 12:23 PM Tomas Vondra
wrote:
> The attached patch is a very simple (and perhaps naive) implementation
> adding count-min sketch to pg_statistic for all attributes with a hash
> function (as a new statistics slot kind), and considering it in
> equijoinsel_inner. There's a G
Hi,
During the recent "CMU vaccination" talk given by Robert [1], a couple
of the attendees (some of which were engineers working on various other
database systems) asked whether PostgreSQL optimizer uses sketches.
Which it does not, as far as I'm aware. Perhaps some of our statistics
could b
