Re: Support for N synchronous standby servers - take 2

On Thu, Jun 25, 2015 at 12:57 PM, Fujii Masao wrote:
> On Thu, Jun 25, 2015 at 12:15 PM, Michael Paquier wrote:
>> and that's actually equivalent to that in
>> the grammar: 1(AAA,BBB,CCC).
>
> I don't think that they are the same. In the case of 1(AAA,BBB,CCC), while
> two servers AAA and BBB are running, the master server may return a success
> of the transaction to the client just after it receives the ACK from BBB.
> OTOH, in the case of AAA,BBB, that never happens. The master must wait for
> the ACK from AAA to arrive before completing the transaction. And then,
> if AAA goes down, BBB should become synchronous standby.

Ah. Right. I missed your point, that's a bad day... We could have
multiple separators to define group types then:
- "()" where the order of acknowledgement does not matter
- "[]" where it does not.
You would find the old grammar with:
1[AAA,BBB,CCC]