Re: Re: COPY FREEZE and setting PD_ALL_VISIBLE/visibility map bits

Hi Pavan,

On 3/14/19 2:20 PM, Masahiko Sawada wrote:
> On Thu, Mar 14, 2019 at 5:17 PM Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> wrote:
>>
>> Ok. I will run some tests. But please note that this patch is a bug fix to address the performance issue that is caused by having to rewrite the entire table when all-visible bit is set on the page during first vacuum. So while we may do some more work during COPY FREEZE, we're saving a lot of page writes during next vacuum. Also, since the scan that we are doing in this patch is done on a page that should be in the buffer cache, we will pay a bit in terms of CPU cost, but not anything in terms of IO cost.
>
> Agreed. I had been misunderstanding this patch. The page scan during
> COPY FREEZE is necessary and it's very cheaper than doing in the first
> vacuum.

I have removed Ibrar as a reviewer since there has been no review from
them in three weeks, and too encourage others to have a look.

Regards,
--
-David
david(at)pgmasters(dot)net