postgres-xc-developers Mailing List for Postgres-XC

Dears,

steps:
postgres=# create sequence seq start with 1;
CREATE SEQUENCE
postgres=# create table t(a int default nextval('seq'), b int);
ERROR:  Could not commit (or autocommit) data node connection

datanode log as follows:
LOG:  statement: create table t(a int default nextval('seq'), b int);
ERROR:  relation "seq" does not exist

When I checked the source code, I found sequence can't be created on
datanodes. Could you explain why?

Regards,
Benny

Continuing on the modifications for 2PC, I finished a patch extending 2PC
file and 2PC xact data protocol.
With the patch attached, 2PC data contains the following information:
- if the 2PC is implicit or explicit
- if the transaction prepared contained DDL or not (if yes, it means that
the transaction has also been prepared on Coordinators)
- the coordinator number from where the 2PC has been issued
- the list of nodes where the transaction has been prepared. In case of a
transaction that prepared only on Coordinators, the list of nodes is set to
"n" (case of sequence transactions)

2PC information below is sent down to nodes when an implicit or explicit
prepare is made, and only on the necessary nodes.

The patch also contains an extension of the view pg_prepared_xacts to be
able to get from catalog table the extended 2PC information as well as the
usual 2PC data.
If you want to make tests, you have to apply first on HEAD
implicit2pc6.patch and then apply
implicit2pc6_extend_pg_prepared_xacts.patch.

I forgot to say that, as pg_prepared_xacts is a catalog view, you have to
connect to a node directly to get the 2PC information.
The information could also be obtained with EXECUTE DIRECT but currently
this functionality is broken.

In the test I did, of course I checked if the views were OK, but also I
checked that recovery of prepared transactions was properly done.
If you want to try, kill a postgres process with SIGQUIT (kill -3) and
relaunch it.
2PC data will recover from the 2PC files correctly. You can check by
launching "select * from pg_prepared_xacts;" before and after stopping the
postgres instance.

Regards,

Michael

-- 
Michael Paquier
http://michaelpq.users.sourceforge.net