Re: increasing the default WAL segment size

On 3/23/17 4:45 PM, Peter Eisentraut wrote:
> On 3/22/17 17:33, David Steele wrote:
>> I think if we don't change the default size it's very unlikely I would
>> use alternate WAL segment sizes or recommend that anyone else does, at
>> least in v10.
>>
>> I simply don't think it would get the level of testing required to be
>> production worthy
>
> I think we could tweak the test harnesses to run all the tests with
> different segment sizes. That would get pretty good coverage.

I would want to see 1,16,64 at a minimum. More might be nice but that
gets a bit ridiculous at some point. I would be fine with different
critters having different defaults. I don't think that each critter
needs to test each value.

> More generally, the methodology that we should not add an option unless
> we also change the default because the option would otherwise not get
> enough testing is a bit dubious.

Generally, I would agree, but I think this is a special case. This
option has been around for a long time and we are just now exposing it
in a way that's useful to end users. It's easy to see how various
assumptions may have arisen around the default and led to code that is
not quite right when using different values. Even if that's not true in
the backend code, it might affect bin, and certainly affects third party
tools.

--
-David
david(at)pgmasters(dot)net