Re: Transactions involving multiple postgres foreign servers

On Fri, Aug 26, 2016 at 11:22 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
wrote:

> On Fri, Aug 26, 2016 at 1:32 PM, Vinayak Pokale <vinpokale(at)gmail(dot)com>
> wrote:
> > Hi All,
> >
> > Ashutosh proposed the feature 2PC for FDW for achieving atomic commits
> > across multiple foreign servers.
> > If a transaction make changes to more than two foreign servers the
> current
> > implementation in postgres_fdw doesn't make sure that either all of them
> > commit or all of them rollback their changes.
> >
> > We (Masahiko Sawada and me) reopen this thread and trying to contribute
> in
> > it.
> >
> > 2PC for FDW
> > ============
> > The patch provides support for atomic commit for transactions involving
> > foreign servers. when the transaction makes changes to foreign servers,
> > either all the changes to all the foreign servers commit or rollback.
> >
> > The new patch 2PC for FDW include the following things:
> > 1. The patch 0001 introduces a generic feature. All kinds of FDW that
> > support 2PC such as oracle_fdw, mysql_fdw, postgres_fdw etc. can involve
> in
> > the transaction.
> >
> > Currently we can push some conditions down to shard nodes, especially in
> 9.6
> > the directly modify feature has
> > been introduced. But such a transaction modifying data on shard node is
> not
> > executed surely.
> > Using 0002 patch, that modify is executed with 2PC. It means that we
> almost
> > can provide sharding solution using
> > multiple PostgreSQL server (one parent node and several shared node).
> >
> > For multi master, we definitely need transaction manager but transaction
> > manager probably can use this 2PC for FDW feature to manage distributed
> > transaction.
> >
> > 2. 0002 patch makes postgres_fdw possible to use 2PC.
> >
> > 0002 patch makes postgres_fdw to use below APIs. These APIs are generic
> > features which can be used by all kinds of FDWs.
> >
> > a. Execute PREAPRE TRANSACTION and COMMIT/ABORT PREAPRED instead of
> > COMMIT/ABORT on foreign server which supports 2PC.
> > b. Manage information of foreign prepared transactions resolver
> >
> > Masahiko Sawada will post the patch.
> >
> >
>
>
Thanks Vinayak and Sawada-san for taking this forward and basing your work
on my patch.

> Still lot of work to do but attached latest patches.
> These are based on the patch Ashutosh posted before, I revised it and
> divided into two patches.
> Compare with original patch, patch of pg_fdw_xact_resolver and
> documentation are lacked.
>

I am not able to understand the last statement.

Do you mean to say that your patches do not have pg_fdw_xact_resolver() and
documentation that my patches had?

OR

you mean to say that my patches did not have (lacked)
pg_fdw_xact_resolver() and documenation

OR some combination of those?
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company