Re: I/O on select count(*)

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

Bruce Momjian <bruce(at)momjian(dot)us> writes:
> Matthew Wakeling wrote:
>> Does it really take that long to zero out 8kB of RAM? I thought CPUs were 
>> really quick at doing that!

> Yea, that was my assumption too.

You have to write the page (to be sure there is space for it on disk)
not only zero it.

This design is kind of a holdover, though, from back when we had one
ever-growing clog file.  Today I'd be inclined to think about managing
it more like pg_xlog, ie, have some background process pre-create a
whole segment file at a time.

			regards, tom lane