Re: Group-count estimation statistics - Mailing list pgsql-hackers

On Fri, 28 Jan 2005, Tom Lane wrote:

> you don't GROUP BY unique combinations of columns over huge
> tables --- or at least, you shouldn't expect great performance if you do.

The proposed change biases towards a hash plan which has no provision for
spilling to disk.  Slow is one thing, but excessive memory usage and
possibly failing is another thing.

Kris Jurka