Re: Freeze avoidance of very large table.

On Mon, Dec 21, 2015 at 11:54 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Dec 21, 2015 at 3:27 AM, Kyotaro HORIGUCHI
> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>> Hello,
>>
>> At Fri, 18 Dec 2015 12:09:43 -0500, Robert Haas <robertmhaas(at)gmail(dot)com> wrote in <CA+TgmoZCCFwgKL0PmSi=htfZ2aCOZPoTPD73ecvSA9rhXa0zUw(at)mail(dot)gmail(dot)com>
>>> On Thu, Dec 17, 2015 at 1:17 AM, Michael Paquier
>>> <michael(dot)paquier(at)gmail(dot)com> wrote:
>>> > I am not really getting the meaning of this sentence. Shouldn't this
>>> > be reworded something like:
>>> > "Freezing occurs on the whole table once all pages of this relation require it."
>>>
>>> That statement isn't remotely true, and I don't think this patch
>>> changes that. Freezing occurs on the whole table once relfrozenxid is
>>> old enough that we think there might be at least one page in the table
>>> that requires it.
>>
>> I doubt I can explain this accurately, but I took the original
>> phrase as that if and only if all pages of the table are marked
>> as "requires freezing" by accident, all pages are frozen. It's
>> quite obvious but it is what I think "happen to require freezing"
>> means. Does this make sense?
>>
>> The phrase might not be necessary if this is correct.
>
> Maybe you are trying to say something like "only those pages which
> require freezing are frozen?".
>

I was thinking the same as what Horiguchi-san said.
That is, even if relfrozenxid is old enough, freezing on the whole
table is not required if the table are marked as "not requires
freezing".
In other word, only those pages which are marked as "not frozen" are frozen.

Regards,

--
Masahiko Sawada