Re: Freeze avoidance of very large table.

On Mon, Nov 2, 2015 at 10:33 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.

Sure. Or we could just keep calling it the visibility map, and then
everyone would know what we're talking about.

--
Robert Haas
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