On Wed, Dec 16, 2020 at 6:22 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Wed, Dec 16, 2020 at 1:04 PM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > > > Thank you for updating the patch. I have two questions: > > > > ----- > > @@ -239,6 +239,19 @@ CREATE SUBSCRIPTION <replaceable > > class="parameter">subscription_name</replaceabl > > </para> > > </listitem> > > </varlistentry> > > + <varlistentry> > > + <term><literal>two_phase</literal> (<type>boolean</type>)</term> > > + <listitem> > > + <para> > > + Specifies whether two-phase commit is enabled for this > > subscription. > > + The default is <literal>false</literal>. > > + When two-phase commit is enabled then the decoded > > transactions are sent > > + to the subscriber on the PREPARE TRANSACTION. When > > two-phase commit is not > > + enabled then PREPARE TRANSACTION and COMMIT/ROLLBACK PREPARED > > are not > > + decoded on the publisher. > > + </para> > > + </listitem> > > + </varlistentry> > > > > The user will need to specify the 'two_phase’ option on CREATE > > SUBSCRIPTION. It would mean the user will need to control what data is > > streamed both on publication side for INSERT/UPDATE/DELETE/TRUNCATE > > and on subscriber side for PREPARE. Looking at the implementation of > > the ’two_phase’ option of CREATE SUBSCRIPTION, it ultimately just > > passes the ‘two_phase' option to the publisher. Why don’t we set it on > > the publisher side? > > > > There could be multiple subscriptions for the same publication, some > want to decode the transaction at prepare time and others might want > to decode at commit time only. Also, one subscription could subscribe > to multiple publications, so not sure if it is even feasible to set at > publication level (consider one txn has changes belonging to multiple > publications). This option controls how the data is streamed from a > publication similar to other options like 'streaming'. Why do you > think this should be any different?
Oh, I was thinking that the option controls what data is streamed similar to the 'publish' option. But I agreed with you. As you mentioned, it might be a problem if a subscription subscribes multiple publications setting different ’two_phase’ options. Also in terms of changing this option while streaming changes, it’s better to control it on the subscriber side. Regards, -- Masahiko Sawada EnterpriseDB: https://www.enterprisedb.com/
