| From: | Thom Brown <thom(at)linux(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, John Gorman <johngorman2(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Parallel Seq Scan |
| Date: | 2015-01-28 14:12:49 |
| Message-ID: | CAA-aLv4cPHaeGWZz3XW2rhrs=cBkf=F3SaW7acAreuSNeTmE7g@mail.gmail.com |
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On 28 January 2015 at 14:03, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> The problem here, as I see it, is that we're flying blind. If there's
> just one spindle, I think it's got to be right to read the relation
> sequentially. But if there are multiple spindles, it might not be,
> but it seems hard to predict what we should do. We don't know what
> the RAID chunk size is or how many spindles there are, so any guess as
> to how to chunk up the relation and divide up the work between workers
> is just a shot in the dark.
Can't the planner take effective_io_concurrency into account?
Thom
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