Re: Transactions involving multiple postgres foreign servers

On Fri, Aug 26, 2016 at 3:03 PM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
>
>
> 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.

Sorry to confuse you.

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

Yes.
I'm confirming them that your patches had.

Regards,

--
Masahiko Sawada