| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, HeikkiLinnakangas <hlinnaka(at)iki(dot)fi> |
| Subject: | Re: Trouble with hashagg spill I/O pattern and costing |
| Date: | 2020-05-29 00:48:11 |
| Message-ID: | f8474785901b8c72fe86096c314908924cc8e5c1.camel@j-davis.com |
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| Lists: | pgsql-hackers |
On Tue, 2020-05-26 at 17:40 -0700, Jeff Davis wrote:
> On Tue, 2020-05-26 at 21:15 +0200, Tomas Vondra wrote:
> > Yeah. I agree prefetching is definitely out of v13 scope. It might
> > be
> > interesting to try how useful would it be, if you're willing to
> > spend
> > some time on a prototype.
>
> I think a POC would be pretty quick; I'll see if I can hack something
> together.
Attached (intended for v14).
I changed the list from a simple array to a circular buffer so that we
can keep enough preallocated block numbers in it to do prefetching.
On SSD I didn't see any improvement, but perhaps it will do better on
magnetic storage.
Regards,
Jeff Davis
| Attachment | Content-Type | Size |
|---|---|---|
| prefetch.diff | text/x-patch | 10.1 KB |
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