From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Question about non-blocking mode in libpq |
Date: | 2023-11-01 02:16:07 |
Message-ID: | 2674201.1698804967@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Bruce Momjian <bruce(at)momjian(dot)us> writes:
> On Tue, Oct 31, 2023 at 09:11:06PM -0400, Tom Lane wrote:
>> What I'm objecting to is removal of the bit about "if they need to be
>> called again". That provides a hint that retry is the appropriate
>> response to a failure. Admittedly, it's not 100% clear, but your
>> version makes it 0% clear.
> I thought the original docs said you had to re-call on failure (it would
> not block but it would fail if it could not be sent), while we are now
> saying that it will be queued in the input buffer.
For these functions in nonblock mode, failure means "we didn't queue it".
> Is retry really something we need to mention now? If out of memory is
> our only failure case now ("unable to enlarge the buffer because OOM"),
> is retry really a realistic option?
Well, ideally the application would do something to alleviate the
OOM problem before retrying. I don't know if we want to go so far
as to discuss that. I do object to giving the impression that
failure is impossible, which I think your proposed wording does.
An orthogonal issue with your latest wording is that it's unclear
whether *unsuccessful* calls to these functions will block.
regards, tom lane
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