Re: reducing statistics write overhead

Tom Lane wrote:
> Martin Pihlak <martin(dot)pihlak(at)gmail(dot)com> writes:
>> I had also previously experimented with stat() based polling but ran into
>> the same issues - no portable high resolution timestamp on files. I guess
>> stat() is unusable unless we can live with 1 second update interval for the
>> stats (eg. backend reads the file if it is within 1 second of the request).
>
>> One alternative is to include a timestamp in the stats file header - the
>> backend can then wait on that -- check the timestamp, sleep, resend the
>> request, loop. Not particularly elegant, but easy to implement. Would this
>> be acceptable?
>
> Timestamp within the file is certainly better than trying to rely on
> filesystem timestamps. I doubt 1 sec resolution is good enough, and

We'd need half a second resolution just to keep up with the level we
have *now*, don't we?

> I'd also be worried about issues like clock skew between the
> postmaster's time and the filesystem's time.

Can that even happen on a local filesystem? I guess you could put the
file on NFS though, but that seems to be.. eh. sub-optimal.. in more
than one way..

//Magnus