Re: Support for N synchronous standby servers - take 2

On Tue, Apr 5, 2016 at 7:23 PM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> At Mon, 4 Apr 2016 22:00:24 +0900, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote in <CAD21AoDoq1ubY4KkKhrA9jzaVXekwAT7gV5pQJbS+wj98b9-3A(at)mail(dot)gmail(dot)com>
>> > For this case, the tree members of SyncRepConfig are '2[Sby1,',
>> > 'Sby2', "Sby3]'. This syntax is valid for the current
>> > specification but will surely get different meaning by the future
>> > changes. We should refuse this known-to-be-wrong-in-future syntax
>> > from now.
>>
>> I couldn't get your point but why will the above syntax meaning be
>> different from current meaning by future change?
>> I thought that another method uses another kind of parentheses.
>
> If the 'another kind of parehtheses' is a pair of brackets, an
> application_name 'tokyo[A]', for example, is currently allowed to
> occur unquoted in the list but will become disallowed by the
> syntax change.
>
>

Thank you for explaining.
I understood but since the future syntax is yet to be reached
consensus, I thought that it would be difficult to refuse particular
kind of parentheses for now.

> > list_member_int() performs the loop internally. So I'm not sure how much
> > adding extra list_member_int() here can optimize this processing.
> > Another idea is to make SyncRepGetSyncStandby() check whether I'm sync
> > standby or not. In this idea, without adding extra loop, we can exit earilier
> > in the case where I'm not a sync standby. Does this make sense?
> The list_member_int() is also performed in the "(snip)" part. So
> SyncRepGetSyncStandbys() returning am_sync seems making sense.
>
> sync_standbys = SyncRepGetSyncStandbys(am_sync);
>
> /*
> * Quick exit if I am not synchronous or there's not
> * enough synchronous standbys
> * /
> if (!*am_sync || list_length(sync_standbys) < SyncRepConfig->num_sync)
> {
> list_free(sync_standbys);
> return false;

I meant that it can skip to acquire spin lock at least, so it will
optimise that logic.
But anyway I agree with making SyncRepGetSyncStandbys returns am_sync variable.

--
Regards,

--
Masahiko Sawada