On Fri, Aug 26, 2016 at 11:22 AM, Masahiko Sawada <sawada.m...@gmail.com> wrote:
> On Fri, Aug 26, 2016 at 1:32 PM, Vinayak Pokale <vinpok...@gmail.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
