| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tomas Vondra <tomas(at)vondra(dot)me>, James Coleman <jtc331(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Consider low startup cost in add_partial_path |
| Date: | 2026-02-17 07:44:39 |
| Message-ID: | CAMbWs4-mO3jMK4t_LgcJ+7Eo=NmGgkxettgRaVbJzZvVZ1koMA@mail.gmail.com |
| Views: | Whole Thread | Raw Message | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Sat, Feb 7, 2026 at 6:06 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I rediscovered this problem while testing pg_plan_advice, and I think
> we should commit something to fix it.
Yeah, I agree that we should consider startup cost for partial paths,
given that cost_gather (and cost_gather_merge) accounts for the
subpath's startup_cost when calculating the cost of the Gather path.
The changes LGTM. I noticed one comment that may need to be updated
accordingly:
* As in add_path, the partial_pathlist is kept sorted with the cheapest
* total path in front. ...
This is not true anymore. The partial_pathlist is now sorted by
disabled_nodes and then by cheapest total cost.
- Richard
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Akshay Joshi | 2026-02-17 07:54:05 | Re: [PATCH] pgindent truncates last line of files missing a trailing newline |
| Previous Message | Michael Paquier | 2026-02-17 07:26:29 | Re: Lowering the default wal_blocksize to 4K |