Re: Hard limit on WAL space used (because PANIC sucks)

On 06/08/2013 11:27 AM, Andres Freund wrote:
>
> On 2013-06-08 11:15:40 -0700, Joshua D. Drake wrote:
>> To me, a more pragmatic approach makes sense. Obviously having some kind of
>> code that checks the space makes sense but I don't know that it needs to be
>> around any operation other than we are creating a segment. What do we care
>> why the segment is being created? If we don't have enough room to create the
>> segment, the transaction rollsback with some OBVIOUS not OBTUSE error.
>>
>> Obviously this could cause a ton of transactions to roll back but I think
>> keeping the database consistent and rolling back a transaction in case of
>> error is exactly what we are supposed to do.
>
> You know, the PANIC isn't there just because we like to piss of
> users. There's actual technical reasons that don't just go away by
> judging the PANIC as stupid.

Yes I know we aren't trying to piss off users. What I am saying is that 
it is stupid to the user that it PANICS. I apologize if that came out wrong.

> At the points where the XLogInsert()s happens we're in critical sections
> out of which we *cannot* ERROR out because we already may have made
> modifications that cannot be allowed to be performed
> partially/unlogged. That's why we're throwing a PANIC which will force a
> cluster wide restart including *NOT* writing any further buffers from
> s_b out.
>

Does this preclude (sorry I don't know this part of the code very well) 
my suggestion of on log create?

JD


> Greetings,
>
> Andres Freund
>