| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Ants Aasma <ants(at)cybertec(dot)at>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Materialized views WIP patch |
| Date: | 2013-03-06 14:16:59 |
| Message-ID: | 14403.1362579419@sss.pgh.pa.us |
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On 5 March 2013 22:02, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
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