Re: Freeze avoidance of very large table.

On Wed, Nov 4, 2015 at 12:19 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Wed, Nov 4, 2015 at 4:45 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
> wrote:
>>
>> On Tue, Nov 3, 2015 at 12:33 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
>> wrote:
>> > On Tue, Nov 3, 2015 at 5:04 AM, Robert Haas <robertmhaas(at)gmail(dot)com>
>> > wrote:
>> >>
>> >> On Sat, Oct 31, 2015 at 1:32 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
>> >> wrote:
>> >> >
>> >> > What is your main worry about changing the name of this map, is it
>> >> > about more code churn or is it about that we might introduce new
>> >> > issues
>> >> > or is it about that people are already accustomed to call this map as
>> >> > visibility map?
>> >>
>> >> My concern is mostly that I think calling it the "visibility and
>> >> freeze map" is excessively long and wordy.
>> >>
>> >> One observation that someone made previously is that there is a
>> >> difference between "all-visible" and "index-only scan OK". An
>> >> all-visible page that has a HOT update is no longer all-visible (it
>> >> needs vacuuming) but an index-only scan would still be OK (because
>> >> only the non-indexed values in the tuple have changed, and every scan
>> >> scan can see either the old or the new tuple but not both. At
>> >> present, the index-only scan will consult the heap page anyway,
>> >> because all we know is that the page is not all-visible. But maybe in
>> >> the future somebody will decide to add a bit for that. Then we'd have
>> >> the "visibility, usable for index-only scans, and freeze map", but I
>> >> think "_vufiosfm" will not be a good choice for a file suffix.
>> >>
>> >
>> > I think in that case we can call it as page info map or page state map,
>> > but
>> > I find retaining visibility map name in this case or for future (if we
>> > want
>> > to
>> > add another bit) as confusing. In-fact if you find "visibility and
>> > freeze
>> > map",
>> > as excessively long, then we can change it to "page info map" or "page
>> > state
>> > map" now as well.
>> >
>>
>> In that case, file suffix would be "_pim" or "_psm"?
>
> Right.
>
>> IMO, "page info map" would be better, because the bit doesn't indicate
>> the status of page in real time, it's just additional information.
>> Also we need to rewrite to new name in source code, and source file
>> name as well.
>>
>
> I think so. Here I think the right thing to do is lets proceed with fixing
> other issues of patch and work on this part later and in the mean time
> we might get more feedback on this part of proposal.
>

Yeah, I'm going to do that changes if there is no strong objection from hackers.

Regards,

--
Masahiko Sawada