Re: [HACKERS] More stats about skipped vacuums

On Sun, Nov 26, 2017 at 3:19 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Sat, Nov 25, 2017 at 12:09 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Mumble. It's a property I'm pretty hesitant to give up, especially
>>> since the stats views have worked like that since day one. It's
>>> inevitable that weakening that guarantee would break peoples' queries,
>>> probably subtly.
>
>> You mean, queries against the stats views, or queries in general? If
>> the latter, by what mechanism would the breakage happen?
>
> Queries against the stats views, of course.

Hmm. Those are probably rare. If we only took a snapshot of the
statistics for the backends that explicitly access those views, that
probably wouldn't be too crazy.

Sorry if this is a stupid question, but how often and for what purpose
to regular backends need the stats collector data for purposes other
than querying the stats views? I thought that the data was only used
to decide whether to VACUUM/ANALYZE, and therefore would be accessed
mostly by autovacuum, and for that you'd actually want the most
up-to-date view of the stats for a particular table that is available,
not any older snapshot.

--
Robert Haas
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