Simon Riggs <simon@2ndQuadrant.com> writes:
> On 5 March 2013 22:02, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> FWIW, my opinion is that doing anything like this in the planner is
>> going to be enormously expensive.
> As we already said: no MVs => zero overhead => no problem.
Well, in the first place that statement is false on its face: we'll
still spend cycles looking for relevant MVs, or at least maintaining a
complexly-indexed cache that helps us find out that there are none in
a reasonable amount of time. In the second place, even if it were
approximately true it wouldn't help the people who were using MVs.
> It costs in
> the cases where time savings are possible and not otherwise.
And that is just complete nonsense: matching costs whether you find a
match or not. Could we have a little less Pollyanna-ish optimism and
a bit more realism about the likely cost of such a feature?
regards, tom lane