Re: Question about non-blocking mode in libpq

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