| 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: | 2020-05-27 00:40:19 |
| Message-ID: | 0589f869969de2f3e9713689159c7c4fbe1fcfa5.camel@j-davis.com |
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| Lists: | pgsql-hackers |
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.
> I think it's pretty much ready to go.
Committed with max of 128 preallocated blocks. Minor revisions.
>
> As for the tlist fix, I think that's mostly ready too - the one thing
> we
> should do is probably only doing it for AGG_HASHED. For AGG_SORTED
> it's
> not really necessary.
Melanie previously posted a patch to avoid spilling unneeded columns,
but it introduced more code:
and it seems that Heikki also looked at it. Perhaps we should get an
acknowledgement from one of them that your one-line change is the right
approach?
Regards,
Jeff Davis
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