Re: [HACKERS] GUC for cleanup indexes threshold.

On Tue, Jun 26, 2018 at 4:11 PM Darafei "Komяpa" Praliaskouski
<me@komzpa.net> wrote:
> вт, 26 июн. 2018 г. в 15:42, Alexander Korotkov <a.korotkov@postgrespro.ru>:
>>
>> On Tue, Jun 26, 2018 at 1:46 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>> > On Fri, Jun 22, 2018 at 6:55 PM, Alexander Korotkov
>> > <a.korotkov@postgrespro.ru> wrote:
>> > > So, I propose to just
>> > > increase maximum value for both GUC and reloption.  See the attached
>> > > patch.  It also changes calculations _bt_vacuum_needs_cleanup() for
>> > > better handling of large values (just some kind of overflow paranoia).
>> >
>> > The patch looks good to me.
>>
>> Pushed, thanks!
>
>
> Thank you for the enhancement. Now Index Only Scans over Append-Only tables in Postgres  can be implemented, even if
itrequires manual kicking of VACUUM over large table, and that's a great enhancement for moving object databases. :) 
>
> My eye catches another thing, the error message in tests is:
>
> DETAIL:  Valid values are between "0.000000" and
"179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000".
>
> a) do we really need to print digits of dblmax? "Valid values are double precision, non-negative"?
> b) double precision binary-to-decimal noise starts at 16th digit. Why does it stop at the point, and we have precise
".000000"?Does it bite the conversion somewhere else too? 

Thank you for pointing.  I'm proposing to change output format from
"%f" to "%g" [1] [2].  It looks better and the same as what we do for
GUCs.

1. https://www.postgresql.org/message-id/CAPpHfdvewmr4PcpRjrkstoNn1n2_6dL-iHRB21CCfZ0efZdBTg%40mail.gmail.com
2. https://www.postgresql.org/message-id/CAPpHfdsFBbJAd24F0b_o9TfTtu%2B%2BjH0bR5XS_e9xbSwk8SJwyQ%40mail.gmail.com

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company