| From: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
|---|---|
| To: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
| Subject: | Re: [DESIGN] ParallelAppend |
| Date: | 2015-11-12 05:48:44 |
| Message-ID: | 5644283C.4040809@lab.ntt.co.jp |
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| Lists: | pgsql-hackers |
On 2015/11/12 14:09, Kouhei Kaigai wrote:
> I'm now designing the parallel feature of Append...
>
> Here is one challenge. How do we determine whether each sub-plan
> allows execution in the background worker context?
>
> The commit f0661c4e8c44c0ec7acd4ea7c82e85b265447398 added
> 'parallel_aware' flag on Path and Plan structure.
> It tells us whether the plan/path-node can perform by multiple
> background worker processes concurrently, but also tells us
> nothing whether the plan/path-node are safe to run on background
> worker process context.
When I was looking at the recent parallelism related commits, I noticed a
RelOptInfo.consider_parallel flag. That and the function
set_rel_consider_parallel() may be of interest in this regard.
set_append_rel_size() passes the parent's state of this flag down to child
relations but I guess that's not what you're after.
Thanks,
Amit
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