Re: Transactions involving multiple postgres foreign servers, take 2

On Fri, 18 Sep 2020 at 17:00, Masahiko Sawada
<masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
>
> On Thu, 17 Sep 2020 at 14:25, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> >
> > On Fri, Aug 21, 2020 at 03:25:29PM +0900, Masahiko Sawada wrote:
> > > Thank you for letting me know. I've attached the latest version patch set.
> >
> > A rebase is needed again as the CF bot is complaining.
>
> Thank you for letting me know. I'm updating the patch and splitting
> into small pieces as Fujii-san suggested. I'll submit the latest patch
> set early next week.
>

I've rebased the patch set and split into small pieces. Here are short
descriptions of each change:

v26-0001-Recreate-RemoveForeignServerById.patch

This commit recreates RemoveForeignServerById that was removed by
b1d32d3e3. This is necessary because we need to check if there is a
foreign transaction involved with the foreign server that is about to
be removed.

v26-0002-Introduce-transaction-manager-for-foreign-transa.patch

This commit adds the basic foreign transaction manager,
CommitForeignTransaction, and RollbackForeignTransaction API. These
APIs support only one-phase. With this change, FDW is able to control
its transaction using the foreign transaction manager, not using
XactCallback.

v26-0003-postgres_fdw-supports-commit-and-rollback-APIs.patch

This commit implements both CommitForeignTransaction and
RollbackForeignTransaction APIs in postgres_fdw. Note that since
PREPARE TRANSACTION is still not supported there is nothing the user
newly is able to do.

v26-0004-Add-PrepareForeignTransaction-API.patch

This commit adds prepared foreign transaction support including WAL
logging and recovery, and PrepareForeignTransaction API. With this
change, the user is able to do 'PREPARE TRANSACTION' and
'COMMIT/ROLLBACK PREPARED' commands on the transaction that involves
foreign servers. But note that COMMIT/ROLLBACK PREPARED ends only the
local transaction. It doesn't do anything for foreign transactions.
Therefore, the user needs to resolve foreign transactions manually by
executing the pg_resolve_foreign_xacts() SQL function which is also
introduced by this commit.

v26-0005-postgres_fdw-supports-prepare-API-and-support-co.patch

This commit implements PrepareForeignTransaction API and makes
CommitForeignTransaction and RollbackForeignTransaction supports
two-phase commit.

v26-0006-Add-GetPrepareID-API.patch

This commit adds GetPrepareID API.

v26-0007-Automatic-foreign-transaciton-resolution-on-COMM.patch

This commit adds the automatic foreign transaction resolution on
COMMIT/ROLLBACK PREPARED by using foreign transaction resolver and
launcher processes. With this change, the user is able to
commit/rollback the distributed transaction by COMMIT/ROLLBACK
PREPARED without manual resolution. The involved foreign transactions
are automatically resolved by a resolver process.

v26-0008-Automatic-foreign-transaciton-resolution-on-comm.patch

This commit adds the automatic foreign transaction resolution on
commit/rollback. With this change, the user is able to commit the
foreign transactions automatically on commit without executing PREPARE
TRANSACTION when foreign_twophase_commit is 'required'. IOW, we can
guarantee that all foreign transactions had been resolved when the
user got an acknowledgment of COMMIT.

v26-0009-postgres_fdw-supports-automatically-resolution.patch

This commit makes postgres_fdw supports the 0008 change.

v26-0010-Documentation-update.patch
v26-0011-Add-regression-tests-for-foreign-twophase-commit.patch

The above commits are documentation update and regression tests.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services