Re: count(*) performance improvement ideas

"Stephen Denne" <Stephen(dot)Denne(at)datamail(dot)co(dot)nz> writes:
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
>> As for 2) and 3), can't you look into the pg_settings view?

> pg_settings view doesn't contain custom variables created on the fly,

Really? [ pokes around ... ] Hm, you're right, because
add_placeholder_variable() sets the GUC_NO_SHOW_ALL flag, and in this
usage it'll never be cleared. I wonder if we should change that.

The whole thing is a bit of an abuse of what the mechanism was intended
for, and so I'm not sure we should rejigger GUC's behavior to make it
more pleasant, but on the other hand if we're not ready to provide a
better substitute ...

regards, tom lane