Re: Re: PATCH: Split stats file per database WAS: autovacuum stress-testing our system

Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> On 05/31/2016 06:59 PM, Tom Lane wrote:
>> I'm confused here --- are you speaking of having removed
>> if (msg->cutoff_time > req->request_time)
>> req->request_time = msg->cutoff_time;
>> ? That is not a check for clock skew, it's intending to be sure that
>> req->request_time reflects the latest request for this DB when we've
>> seen more than one request. But since req->request_time isn't
>> actually being used anywhere, it's useless code.

> Ah, you're right. I've made the mistake of writing the e-mail before
> drinking any coffee today, and I got distracted by the comment change.

>> I reformatted the actual check for clock skew, but I do not think I
>> changed its behavior.

> I'm not sure it does not change the behavior, though. request_time only
> became unused after you removed the two places that set the value (one
> of them in the clock skew check).

Well, it's unused in the sense that the if-test quoted above is the only
place in HEAD that examines the value of request_time. And since that
if-test only controls whether we change the value, and not whether we
proceed to make the clock skew check, I don't see how it's related
to clock skew or indeed anything else at all.

regards, tom lane