Re: query optimization question

On Thu, 29 Jan 2004, Tom Lane wrote:

> > jackdb-# GROUP BY memberid_ HAVING (
>
> Um, that's not what I had in mind at all.  Does GROUP BY actually do
> anything at all here?  (You didn't answer me as to whether memberid_
> is a unique identifier or not, but if it is, this GROUP BY is just an
> expensive no-op.)

From your comment I assume that there is no transformation in pg that
detects that the group by columns are unique?

> this is all blue-sky speculation anyway.  What I'm actually more
> interested in is your statement that MSSQL can do the original query
> quickly.  I find that a bit hard to believe because I don't see any
> relevant optimization techniques.

Getting rid of the group by would not give that kind of speedup? Maybe
mssql manage to rewrite the query like that before executing.

--
/Dennis Björklund