| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
| Cc: | Merlin Moncure <mmoncure(at)gmail(dot)com>, David Greco <David_Greco(at)harte-hanks(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Poor performance using CTE |
| Date: | 2012-11-20 23:44:51 |
| Message-ID: | CAGTBQpZ9zfVLn8wqxOi5sQJ2P+VtE5YksNGSmQD0aH_oDOOGkQ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Nov 20, 2012 at 8:38 PM, Craig Ringer <craig(at)2ndquadrant(dot)com> wrote:
> On 11/21/2012 12:06 AM, Claudio Freire wrote:
>> I meant for postgres to do automatically. Rewriting as a join wouldn't
>> work as an optimization fence the way we're used to, but pushing
>> constraints upwards can only help (especially if highly selective).
> Because people are now used to using CTEs as query hints, it'd probably
> cause performance regressions in working queries. Perhaps more
> importantly, Pg would have to prove that doing so didn't change queries
> that invoked functions with side-effects to avoid changing the results
> of currently valid queries.
Fair point. Will look into it a bit.
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