Re: MAX/MIN optimization via rewrite (plus query rewrites generally)

On Wed, Nov 10, 2004 at 07:18:59PM -0500, Tom Lane wrote:

> A more radical way of handling it would be to detect the relevance of an
> indexscan in indxpath.c and generate a special kind of Path node; this
> would not generalize to other sorts of things as you were hoping, but
> I'm unconvinced that the mechanism is going to be very general-purpose
> anyway.  The major advantage is that this would work conveniently for
> comparing the cost of a rewritten query to a non-rewritten one.

What about having a new column in pg_aggregate which would point to a
function that would try to optimize the aggregate's handling?

There could be multiple calls to that function along the query's way to
executor, each one at a different point (with a parameter specifying
which one it is), that would try to rewrite the query optimizing the
aggregate.  So we could optimize some aggregates at one point, and
others at a different point, whichever makes the most sense.

-- 
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"Hay dos momentos en la vida de un hombre en los que no debería
especular: cuando puede permitírselo y cuando no puede" (Mark Twain)