Re: So, is COUNT(*) fast now?

Andres Freund <andres@anarazel.de> writes:
> On Saturday, October 22, 2011 05:20:26 PM Tom Lane wrote:
>> Huh?  In the case he's complaining about, the index is all in RAM.
>> Sequentiality of access is not an issue (at least not at the page
>> level --- within a page I suppose there could be cache-line effects).

> I was talking about L2/L3 caches...

Yeah, but unless you think cache lines cross page boundaries (and we do
take pains to align the buffers on 8K addresses), there's not going to
be any sequentiality effect.  Even if there were, it would only apply
if the pages chanced to be adjacent in the buffer array, and there is no
reason to expect that to be the case, for either seqscans or indexscans.
        regards, tom lane