Re: Online enabling of checksums

On 08/01/2018 05:58 PM, Andres Freund wrote:
> Hi,
> 
> On 2018-08-01 11:15:38 +0200, Tomas Vondra wrote:
>> On 08/01/2018 10:40 AM, Michael Banck wrote:
>>> If this was one week before feature freeze, I would agree with you
>>> that it makes sense to ship it with the restart requirement rather
>>> than not shipping it at all. But we're several commitfests away from
>>> v12, so making an effort to having this work without a downtime
>>> looks like a reasonable requirement to me.
>>>
>>
>> Why would all those pieces had to be committed at once? Why not to
>> commit what we have now (with the restart) and then remove the
>> restriction in a later commit?
> 
> Sure, if all the pieces existed in various degrees of solidness (with
> the earlier pieces committable, but later ones needing work), I'd feel
> *much* less concerned about it.
> 

That's not what I meant, sorry for not being clearer. My point was that 
I see the "without restart" as desirable but optional, and would not 
mind treating it as a future improvement.

> 
>> In a way, the question is how far can we reasonably push the patch
>> author(s) to implement stuff we consider desirable, but he/she/they
>> decided it's not worth the time investment at this point.
> 
> We push people to only implement something really consistent all the
> time.
> 

Sure, but it's somewhat subjective matter - to me this limitation does 
not make this particular patch inconsistent. If we can remove it, great. 
If not, it's still immensely useful improvement.

> 
>> To me, it seems like an immensely useful feature even with the restart,
>> and I don't think the restart is a major burden for most systems (it can
>> be, if your system has no maintenance windows, or course).
> 
> I think it a problem, my problem is more that I don't think it's really
> a solution for the problem.
> 

Sure, if there are issues with this approach, that would make it 
unacceptable. I'm not sure why would it be an issue for replicas (which 
is what you mention elsewhere), considering those don't write data and 
so can't fail to update a checksum?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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