Re: count * performance issue

Robins Tharakan wrote:
> Hi,
>
> I have been reading this conversation for a few days now and I just
> wanted to ask this. From the release notes, one of the new additions
> in 8.3 is (Allow col IS NULL to use an index (Teodor)).
>
> Sorry, if I am missing something here, but shouldn't something like
> this allow us to get a (fast) accurate count ?
>
> SELECT COUNT(*) from table WHERE indexed_field IS NULL
> +
> SELECT COUNT(*) from table WHERE indexed_field IS NOT NULL

For PostgreSQL: You still don't know whether the row is visible until
you check the row. That it's NULL or NOT NULL does not influence this truth.

Cheers,
mark

--
Mark Mielke <mark(at)mielke(dot)cc>