On Wed, Apr 13, 2016 at 7:13 AM, Darren Duncan <darren@darrenduncan.net> wrote:
> On 2016-04-12 10:54 AM, Robert Haas wrote:
>>
>> On Tue, Apr 12, 2016 at 8:59 AM, Justin Clift <justin@postgresql.org>
>> wrote:
>>>
>>> On 12 Apr 2016, at 13:37, Robert Haas <robertmhaas@gmail.com> wrote:
>>>>
>>>> On Tue, Apr 12, 2016 at 3:21 AM, Magnus Hagander <magnus@hagander.net>
>>>> wrote:
>>>>>
>>>>> I think that may turn out to be one of those "hidden gems" of this
>>>>> release.
>>>>> As in being the one that nobody talks about now, but then a few years
>>>>> down
>>>>> the road it's the one that everybody talks about. But it's somewhat
>>>>> hard to
>>>>> explain to people who (1) don't know how the system really works
>>>>> (though
>>>>> that would count for things like snapshot too old as well) or (2)
>>>>> actually
>>>>> have run into the current problem (why hey, that's also the same with
>>>>> snapshot too old)
>>>>
>>>>
>>>> Agreed. Unfortunately, for many people, the first time they really
>>>> become aware of autovacuum is when all of their tables hit the freeze
>>>> threshold for the first time. And this doesn't help with that. You
>>>> still have to scan everything after 200 million transactions; it's
>>>> just that you no longer have to do it again every 200 million
>>>> transactions after that. I still think it's a great feature, though.
>>>
>>>
>>> Er... we don't provide a warning ahead of time in the logs or something?
>>
>>
>> No. That would be a little strange, honestly. I have to assume that
>> many wraparound vacuums go totally unnoticed; how would you
>> distinguish the ones that are likely to annoy somebody from the other
>> ones?
>
>
> I suggest providing a config option for those warnings, if there isn't one
> already. Global plus override per table etc. The option says we only log
> the warnings if the wraparound vacuum is likely to take more than a certain
> amount of time, and pick something reasonable for that default time. Or to
> generalize, have a config saying what to do if a wraparound vacuum is coming
> up soon, including what amount of estimated time may be considered
> inconvenient. -- Darren Duncan
postgres users no longer care about anti-wraparound vacuum at 9.6 and
postgres already emits WARNING log at 10 million transaction
remaining.
Regards,
--
Masahiko Sawada
