Re: Expensive log_line_prefix ?

Tom Lane escribió:
> Sergey Konoplev <gray(dot)ru(at)gmail(dot)com> writes:
> > On Thu, Oct 11, 2012 at 12:19 PM, Sahagian, David
> > <david(dot)sahagian(at)emc(dot)com> wrote:
> >> Are there any "extra" costs to logging all this cool stuff ?
> >>
> >> log_line_prefix = '%m %a %u %p %c %m %v %x'
>
> > The formatting cost only but it is so insignificant that does not
> > worth bothering with it.
>
> IIRC, %m would imply a gettimeofday call, which might be expensive
> depending on your OS and hardware. I think all the other info is
> "just sitting around", though.

Yeah, and having two %m means two gettimeofday calls.

Also, %c sort of implies %p, so having both is probably just a waste.

One other point is that it's probably a good idea to put in a %q in
there so that processes that don't have things like %v, %x don't have to
print a bunch of zeros (and also to prevent %a, %u from adding spaces
unnecessarily).

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Álvaro Herrera http://www.2ndQuadrant.com/
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