Re: Functional dependencies and GROUP BY

On lör, 2010-07-17 at 11:13 -0600, Alex Hunsaker wrote:
> its really no surprise that your test with 1600 columns had little
> effect. As it loops over the the indexes, then the index keys and
> then the group by items right? So I would expect the more indexes you
> had or group by items to slow it down. Not so much the number of
> columns. Right?

At the outer level (which is not visible in this patch) it loops over
all columns in the select list, and then it looks up the indexes each
time. So the concern was that if the select list was * with a wide
table, looking up the indexes each time would be slow.

> Anyhow it sounds like I should try it on top of the other patch and
> see if it works. I assume it might still need some fixups to work
> with that other patch? Or do you expect it to just work?

There is some work necessary to integrate the two.