On Thu, Aug 11, 2022 at 1:48 AM Matthias van de Meent
wrote:
> I think I understand your reasoning, but I don't agree with the
> conclusion. The attached patch 0002 does fix that skew too, at what I
> consider negligible cost. 0001 is your patch with a new version
> number.
Your patch added allow
On Mon, 8 Aug 2022 at 18:48, Peter Geoghegan wrote:
>
> On Mon, Aug 8, 2022 at 9:17 AM Matthias van de Meent
> wrote:
> > Because if a subset of the pages of a relation contains more tuples
> > than your current total expected tuples in the table, you should
> > update your expectations regardles
On Mon, Aug 8, 2022 at 9:17 AM Matthias van de Meent
wrote:
> Because if a subset of the pages of a relation contains more tuples
> than your current total expected tuples in the table, you should
> update your expectations regardless of which blocks or which number of
> blocks you've scanned - th
On Mon, 8 Aug 2022 at 17:49, Peter Geoghegan wrote:
>
> On Mon, Aug 8, 2022 at 8:33 AM Matthias van de Meent
> wrote:
> > For example, if currently the measured 2% of the pages contains more
> > than 100% of the previous count of tuples, or with your patch the last
> > page contains more than 100
On Mon, Aug 8, 2022 at 8:33 AM Matthias van de Meent
wrote:
> For example, if currently the measured 2% of the pages contains more
> than 100% of the previous count of tuples, or with your patch the last
> page contains more than 100% of the previous count of the tuples, that
> new count is ignore
On Mon, 8 Aug 2022 at 17:26, Peter Geoghegan wrote:
>
> On Mon, Aug 8, 2022 at 8:14 AM Matthias van de Meent
> wrote:
> > I do not have intimate knowledge of this code, but shouldn't we also
> > add some sefety guarantees like the following in these blocks? Right
> > now, we'll keep underestimati
On Mon, Aug 8, 2022 at 8:14 AM Matthias van de Meent
wrote:
> I do not have intimate knowledge of this code, but shouldn't we also
> add some sefety guarantees like the following in these blocks? Right
> now, we'll keep underestimating the table size even when we know that
> the count is incorrect
On Mon, 8 Aug 2022 at 16:52, Peter Geoghegan wrote:
>
> On Fri, Aug 5, 2022 at 5:39 PM Peter Geoghegan wrote:
> > Attached patch fixes closes the remaining gap. With the patch applied,
> > the second and subsequent vacuum verbose operations from the test case
> > will show that reltuples is still
On Fri, Aug 5, 2022 at 5:39 PM Peter Geoghegan wrote:
> Attached patch fixes closes the remaining gap. With the patch applied,
> the second and subsequent vacuum verbose operations from the test case
> will show that reltuples is still 1 (it won't ever change). The
> patch just extends an old
My bugfix commit 74388a1a (which was pushed back in February) added
heuristics to VACUUM's reltuples calculation/estimate. This prevented
VACUUM from distorting our estimate of reltuples over time, across
successive VACUUM operations run against the same table. The problem
was that VACUUM could sca
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