From: Antonin Houska <ah@cybertec.at>
To: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
cc: pgsql-hackers@postgresql.org
Subject: Re: asynchronous execution
In-reply-to: <20170622.141720.190958545.horiguchi.kyotaro@lab.ntt.co.jp>
References: <20170404.192539.29699823.horiguchi.kyotaro@lab.ntt.co.jp>
 <20170522.131214.20936668.horiguchi.kyotaro@lab.ntt.co.jp>
 <20170522.142253.40733906.horiguchi.kyotaro@lab.ntt.co.jp>
 <20170622.141720.190958545.horiguchi.kyotaro@lab.ntt.co.jp>
Comments: In-reply-to Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
   message dated "Thu, 22 Jun 2017 14:17:20 +0900."
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Date: Wed, 28 Jun 2017 20:22:24 +0200
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Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote:

> The patch got conflicted. This is a new version just rebased to
> the current master. Furtuer amendment will be taken later.

Just one idea that I had while reading the code.

In ExecAsyncEventLoop you iterate estate->es_pending_async, then move the
complete requests to the end and finaly adjust estate->es_num_pending_async=
 so
that the array no longer contains the complete requests. I think the point =
is
that then you can add new requests to the end of the array.

I wonder if a set (Bitmapset) of incomplete requests would make the code mo=
re
efficient. The set would contain position of each incomplete request in
estate->es_num_pending_async (I think it's the myindex field of
PendingAsyncRequest). If ExecAsyncEventLoop used this set to retrieve the
requests subject to ExecAsyncNotify etc, then the compaction of
estate->es_pending_async wouldn't be necessary.

ExecAsyncRequest would use the set to look for space for new requests by
iterating it and trying to find the first gap (which corresponds to complet=
ed
request).

And finally, item would be removed from the set at the moment the request
state is being set to ASYNCREQ_COMPLETE.

--=20
Antonin Houska
Cybertec Sch=C3=B6nig & Sch=C3=B6nig GmbH
Gr=C3=B6hrm=C3=BChlgasse 26
A-2700 Wiener Neustadt
Web: http://www.postgresql-support.de, http://www.cybertec.at


--=20
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