On 6 September 2016 at 19:23, Robert Haas <robertmhaas@gmail.com> wrote:
> On Tue, Sep 6, 2016 at 2:16 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> What occurs to me is that we can exactly predict how many tuples we
>> are going to get when we autovacuum, since we measure that and we know
>> what the number is when we trigger it.
>>
>> So there doesn't need to be any guessing going on at all, nor do we
>> need it to be flexible.
>
> No, that's not really true. A lot can change between the time it's
> triggered and the time it happens, or even while it's happening.
> Somebody can run a gigantic bulk delete just after we start the
> VACUUM.
Which wouldn't be removed by the VACUUM, so can be ignored.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
