Re: [HACKERS] logical decoding of two-phase transactions

On 31.01.2017 09:29, Michael Paquier wrote:

On Fri, Jan 27, 2017 at 8:52 AM, Craig Ringer <craig@2ndquadrant.com> wrote:

Now, if it's simpler to just xlog the gid at COMMIT PREPARED time when
wal_level >= logical I don't think that's the end of the world. But
since we already have almost everything we need in memory, why not
just stash the gid on ReorderBufferTXN?

I have been through this thread... And to be honest, I have a hard
time understanding for which purpose the information of a 2PC
transaction is useful in the case of logical decoding. The prepare and
commit prepared have been received by a node which is at the root of
the cluster tree, a node of the cluster at an upper level, or a
client, being in charge of issuing all the prepare queries, and then
issue the commit prepared to finish the transaction across a cluster.
In short, even if you do logical decoding from the root node, or the
one at a higher level, you would care just about the fact that it has
been committed.

 in any state. So there three records in the WAL: PREPARE, PRECOMMIT, COMMIT_PREPARED and
recovery can involve either all of them, either PRECOMMIT+COMMIT_PREPARED either just COMMIT_PREPARED.

--
Konstantin Knizhnik

Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers