| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com> |
| Cc: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, amul sul <sulamul(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Runtime Partition Pruning |
| Date: | 2018-04-04 02:31:17 |
| Message-ID: | CAKJS1f89iTbmxb+Lav4a8Mt5QZ15iv4sqc2GDH2umJs+RbSXpA@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On 4 April 2018 at 14:10, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> On 4 April 2018 at 05:44, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com> wrote:
>> The attached case doesn't trigger a generic plan, so basically all time is
>> spent in GetCachedPlan.
>
> Yeah, there's still no resolution to the fact that a generic plan +
> runtime pruning might be cheaper than a custom plan. The problem is
> the generic plan appears expensive to the custom vs generic plan
> comparison due to it containing more Append subnodes and the run-time
> pruning not being taking into account by that comparison.
Just for the record, some of the benchmarks I did above also used the
attached patch for the -M prepared case.
I didn't intend the patch for PostgreSQL, but I am starting to think
that it would be useful to have something to save from having to
EXECUTE PREPAREd statements 5 times before getting a generic plan.
Doing that is starting to seem a bit fragile to me. Would be nice to
have some solution, but I've so far not thought of anything better
than the attached (incomplete) patch.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| Attachment | Content-Type | Size |
|---|---|---|
| 0001-Add-force_generic_plan-GUC.patch | application/octet-stream | 3.0 KB |
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Craig Ringer | 2018-04-04 02:40:16 | Re: PostgreSQL's handling of fsync() errors is unsafe and risks data loss at least on XFS |
| Previous Message | Peter Eisentraut | 2018-04-04 02:31:14 | Re: [PATCH] Logical decoding of TRUNCATE |