MIME-Version: 1.0
References: <CAPmGK15YigmZKzVBGYPdmo-QMHBdhNupK8L6kUBdUtMERkbXsQ@mail.gmail.com>
 <67cad2e7-f9c1-5eb0-a0be-99fd78571906@oss.nttdata.com> <CAPmGK143nF7BQW0cFv3tpae7FrdYQfKH7eUE+CgwG5c6QGkZ=g@mail.gmail.com>
 <20230417.173812.452521384661813597.horikyota.ntt@gmail.com>
 <CAGECzQThFfOSf_J87pXO1oLY5=45A0deC=x0LsrpWMhO7GSs4w@mail.gmail.com> <53f03117-087f-5583-2c97-e82a3e9dc43e@oss.nttdata.com>
In-Reply-To: <53f03117-087f-5583-2c97-e82a3e9dc43e@oss.nttdata.com>
From: Kuwamura Masaki <kuwamura@db.is.i.nagoya-u.ac.jp>
Date: Thu, 27 Jul 2023 20:01:56 +0900
Message-ID: <CAMyC8qrjv2=oSV6bNC6TWbb01SyW1Se7Lyy7gZFfpVH5bCB6-w@mail.gmail.com>
Subject: Re: Issue in postgres_fdw causing unnecessary wait for cancel request reply
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Jelte Fennema <postgres@jeltef.nl>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, etsuro.fujita@gmail.com, 
	pgsql-hackers@lists.postgresql.org
Content-Type: multipart/alternative; boundary="000000000000c091d2060175e69e"
Archived-At: <https://www.postgresql.org/message-id/CAMyC8qrjv2%3DoSV6bNC6TWbb01SyW1Se7Lyy7gZFfpVH5bCB6-w%40mail.gmail.com>
Precedence: bulk

--000000000000c091d2060175e69e
Content-Type: text/plain; charset="UTF-8"

Hi, Fujii-san

> Regarding the WARNING message, another idea is to pass the return value
> of PQgetCancel() directly to PQcancel() as follows. If NULL is passed,
> PQcancel() will detect it and set the proper error message to errbuf.
> Then the warning message "WARNING:  could not send cancel request:
> PQcancel() -- no cancel object supplied" is output.

I agree to go with this.

With this approach, the information behind the error (e.g., "out of
memory") will disappear, I guess.
I think we have to deal with it eventually. (I'm sorry, I don't have a good
idea right now)
However, the original issue is unnecessary waiting, and this should be
fixed soon.
So it is better to fix the problem this way and discuss retaining
information in another patch IMO.

I'm afraid I'm new to reviewing.
If I'm misunderstanding something, please let me know.

Masaki Kuwamura

--000000000000c091d2060175e69e
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div>Hi, Fujii-san<br><br>&gt; Regarding the WARNING messa=
ge, another idea is to pass the return value<br>&gt; of PQgetCancel() direc=
tly to PQcancel() as follows. If NULL is passed,<br>&gt; PQcancel() will de=
tect it and set the proper error message to errbuf.<br>&gt; Then the warnin=
g message &quot;WARNING: =C2=A0could not send cancel request:<br>&gt; PQcan=
cel() -- no cancel object supplied&quot; is output.<br><br>I agree to go wi=
th this. <br><br>With this approach, the information behind the error (e.g.=
, &quot;out of memory&quot;) will disappear, I guess.<br>I think we have to=
 deal with it eventually. (I&#39;m sorry, I don&#39;t have a good idea righ=
t now)<br>However, the original issue is unnecessary waiting, and this shou=
ld be fixed soon.<br>So it is better to fix the problem this way and discus=
s retaining information in another patch IMO.<br><br>I&#39;m afraid I&#39;m=
 new to reviewing.<br>If I&#39;m misunderstanding something, please let me =
know.<br><br>Masaki Kuwamura<br></div></div>

--000000000000c091d2060175e69e--