Date: Tue, 31 Oct 2023 17:16:56 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Yugo NAGATA <nagata@sraoss.co.jp>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	pgsql-hackers@postgresql.org
Subject: Re: Question about non-blocking mode in libpq
Message-ID: <ZUFuyJtiEXRQE8zi@momjian.us>
References: <20210719231129.b2ab655c0d0e80545274c86f@sraoss.co.jp>
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 <20210721101509.7e70e0f801a4457a2f6a6174@sraoss.co.jp>
 <ZUEyKtrtl3IoTwWW@momjian.us>
 <2604997.1698775114@sss.pgh.pa.us>
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On Tue, Oct 31, 2023 at 01:58:34PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > I modified your patch, attached, that I would like to apply to all
> > supported versions.
> 
> This seems to have lost the information about what to do if these
> functions fail.  I think probably the only possible failure cause
> in nonblock mode is "unable to enlarge the buffer because OOM",
> but that's certainly not the same thing as "cannot fail".

Okay, I added "_successful_ calls", attached.  I am not sure what else
to add.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.

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diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 64b2910fee..9e0563d7ca 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -5316,11 +5316,11 @@ int PQsetnonblocking(PGconn *conn, int arg);
       </para>
 
       <para>
-       In the nonblocking state, calls to
+       In the nonblocking state, successful calls to
        <xref linkend="libpq-PQsendQuery"/>, <xref linkend="libpq-PQputline"/>,
        <xref linkend="libpq-PQputnbytes"/>, <xref linkend="libpq-PQputCopyData"/>,
-       and <xref linkend="libpq-PQendcopy"/> will not block but instead return
-       an error if they need to be called again.
+       and <xref linkend="libpq-PQendcopy"/> will not block;  their changes
+       are stored in the local output buffer until they are flushed.
       </para>
 
       <para>

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