Re: vacuumdb --analyze-only scans all pages?

On 12/28/2016 11:54 PM, Gerhard Wiesinger wrote:
> Hello,
>
> PostgreSQl 9.6.1: after a pg_dump/restore procedure it scans all pages
> (at least for some of the tables, analyze-only switch is specified).
>
> I would expect that only the sample rows are scanned.
>
> "log_details": scanned 2133350 of 2133350 pages
>
> vacuumdb --analyze-only --all --verbose
> INFO: analyzing "public.log"
> INFO: "log": scanned 30000 of 30851 pages, containing 3599899 live rows
> and 0 dead rows; 30000 rows in sample, 3702016 estimated total rows
> INFO: analyzing "public.log_details"
> INFO: "log_details": scanned 2133350 of 2133350 pages, containing
> 334935843 live rows and 0 dead rows; 3000000 rows in sample, 334935843
> estimated total rows
> INFO: analyzing "public.log_details_str"
> INFO: "log_details_str": scanned 30000 of 521126 pages, containing
> 3601451 live rows and 0 dead rows; 30000 rows in sample, 62560215
> estimated total rows
>
> Any ideas why?

I would say because the '3000000 rows in sample' where spread out over
all 2133350 pages.

>
> Thnx.
>
> Ciao,
>
> Gerhard
>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com