Re: Problem while setting the fpw with SIGHUP

On Wed, Apr 18, 2018 at 10:37 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Fri, Apr 13, 2018 at 10:36 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Thu, Apr 12, 2018 at 9:29 PM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>>> Still does it matter when the change is effective?
>>
>> I don't really care deeply about when the change takes effect, but I
>> do care about whether the time when the system *says* the change took
>> effect is the same as when it *actually* took effect. If those aren't
>> the same, it's confusing.
>>
>
> So, what in your opinion is the way to deal with this? If we make it
> a PGC_POSTMASTER parameter, it will have a very clear behavior and
> users don't need to bother whether they have a risk of torn page
> problem or not and as a side-impact the code will be simplified as
> well. However, as Michael said the people who get the benefit of this
> option by disabling/enabling this parameter might complain. Keeping
> it as a SIGHUP option has the drawback that even after the user has
> enabled it, there is a risk of torn pages.

I would just document the risks. If the documentation says that you
can't rely on the value until after the next checkpoint, or whatever
the rule is, then I think we're fine. I don't think that we really
have the infrastructure to do any better; if we try, we'll just end up
with odd warts. Documenting the current set of warts is less churn
and less work.

--
Robert Haas
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