| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
| Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, Zhihong Yu <zyu(at)yugabyte(dot)com>, "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: GROUP BY optimization |
| Date: | 2022-08-18 01:32:14 |
| Message-ID: | CAApHDvr+95wJcABsqSXWcBa+yyUmJ2bq_mnZs9dUnaOi3XRVMg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, 18 Aug 2022 at 02:46, Tomas Vondra
<tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
> So I don't think the current costing is wrong, but it certainly is more
> complex. But the test does not test what it intended - I have two ideas
> how to make it work:
>
> 1) increase the number of rows in the table
>
> 2) increase cpu_operator_cost (for that one test?)
>
> 3) tweak the costing somehow, to increase the cost a bit
Why not, 4) SET parallel_setup_cost = 0; there are plenty of other
places we do just that so we get a parallel plan without having to
generate enough cost to drown out the parallel worker startup cost.
Here are a couple of patches to demo the idea.
David
| Attachment | Content-Type | Size |
|---|---|---|
| fix_partitionwise_aggregate_test_master.patch | text/plain | 2.1 KB |
| fix_partitionwise_aggregate_test_pg15.patch | text/plain | 7.7 KB |
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