Re: Common case not at all clear

Hello David,

I have attached a proposed doc update that makes the problem clearer. I
think that this is important because if people do not understand it they
will write buggy code and then blame Postgresql for losing updates, which
is totally unacceptable. So please do action this. I have tested and
confirm that the behaviour is as I specify.

There is more that could be said, e.g. why to avoid SHARE locks. But I
think that that is enough.

(I personally think that the default semantics are very dubious. Either
Repeatable Read should be the default mode, or updating a row already read
but changed should produce an error for Read Committed. The goal is not to
satisfy academic rules but produce something that works safely in
practice. But I am sure there has been much discussion about that
elsewhere.)

On Fri, Jul 30, 2021 at 6:03 PM Anthony Berglas <anthony(at)berglas(dot)org> wrote:

> OK, I'll put something for you to review. Most programmers simply ignore
> locking and wonder why it sometimes goes wrong.
>
> On Fri, Jul 30, 2021 at 2:22 PM David G. Johnston <
> david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
>> On Thu, Jul 29, 2021 at 8:44 PM Anthony Berglas <anthony(at)berglas(dot)org>
>> wrote:
>>
>>> My point is that while I can follow the academic style discussion, most
>>> of my colleagues could not. They just need to have a clear idea of how to
>>> handle the common case, which is to use a database using some programming
>>> language.
>>>
>>
>> On the whole I believe that we are both mostly correct in our
>> observations. I would be happy to review a change to this section of the
>> documentation - whether done surgically or in a larger patch to make this
>> resource much more accessible to users. I don't plan to take on the
>> activity of putting together an initial patch for consideration. I will
>> observe that there haven't been many questions or comments pertaining to
>> this material hitting the mailing lists; though why that may be is
>> difficult to guess. Maybe it's covered better in books so people just
>> don't use this as a resource for the topic? In any case, the ability for
>> someone that knows this material well, but is a coder and not a teacher, to
>> write up something better and more accessible, and judging this is be a
>> better use of their time than some other activity, is fairly low. It does
>> seem, however, like an excellent project for someone who benefits from the
>> open source nature of the project and is looking for a way to both give
>> back to the community and learn a topic more fully at the same time.
>>
>> David J.
>>
>>
>>
>>