At Wed, 19 Apr 2017 03:03:38 +0900, Fujii Masao <masao.fu...@gmail.com> wrote in <CAHGQGwE95S5GM9UZh0F3ef2D3iEwJ59skh=eww5hmdjpe2a...@mail.gmail.com> > On Tue, Apr 18, 2017 at 7:02 PM, Masahiko Sawada <sawada.m...@gmail.com> > wrote: > > On Tue, Apr 18, 2017 at 6:40 PM, Kyotaro HORIGUCHI > > <horiguchi.kyot...@lab.ntt.co.jp> wrote: > >> At Tue, 18 Apr 2017 14:58:50 +0900, Masahiko Sawada > >> <sawada.m...@gmail.com> wrote in > >> <cad21aobqsjugx0lcdrjedlb-yx2evglmdt8nz4zr_xpxrbm...@mail.gmail.com> > >>> On Tue, Apr 18, 2017 at 3:04 AM, Fujii Masao <masao.fu...@gmail.com> > >>> wrote: > >>> > On Wed, Apr 12, 2017 at 2:36 AM, Masahiko Sawada > >>> > <sawada.m...@gmail.com> wrote: > >>> > This description looks misleading. A quorum-based sync rep is basically > >>> > more efficient when there are multiple standbys in s_s_names and you > >>> > want > >>> > to replicate the transactions to some of them synchronously. I think > >>> > that > >>> > this assumption should be documented explicitly. So I modified this > >>> > description. Please see the modified version in the attached patch. > >>> > >>> You're right. The modified version looks good to me, thanks.
+ A quorum-based synchronous replication is basically more efficient than + a priority-based one when you specify multiple standbys in + <varname>synchronous_standby_names</> and want to replicate + the transactions to some of them synchronously. In this case, + the transactions in a priority-based synchronous replication must wait for + reply from the slowest standby in synchronous standbys chosen based on + their priorities, and which may increase the transaction latencies. + On the other hand, using a quorum-based synchronous replication may + improve those latencies because it makes the transactions wait only for + replies from the requested number of faster standbys in all the listed + standbys, i.e., such slow standby doesn't block the transactions. > >> It looks better to me, too. But (even I'm not sure, of course) > >> the sentences seem to need improvement. > >> > >> | <para> > >> | Quorum-based synchronous replication is basically more > >> | efficient than priority-based one when you specify multiple > >> | standbys in <varname>synchronous_standby_names</> and want > >> | to synchronously replicate transactions to two or more of > >> | them. In the priority-based case, the replication master > >> | must wait for a reply from the slowest standby in the > >> | required number of standbys in priority order, which may > >> | slower than the rest. > > > > I supposed that Fujii-san pointed out that quorum-based sync > > replication could be more efficient when we want to replicate the > > transaction to "part of" standbys listed in s_s_names. > > Yes. Yes, am I wrote something opposing? > Anyway, I pushed the patch except this paragraph. > Regarding this paragraph, the patch for better descriptions is welcome. +1 regards, -- Kyotaro Horiguchi NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
