Re: 2PC support for pglogical

On 24 March 2016 at 22:20, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru> wrote:

>
> I think all the locking already handled properly by creating dummy backend
> in PGPROC, as it done in usual postgres 2pc implementation.
>
>
On the downstream, yes. But what about the decoding, reorder buffer and
output plugin? They access the relcache etc. If you changed the structure
of a table in a prepared xact you have to make sure you get that right.

> Just checked DDL with following scenario:
>
> * prepare tx that inserts a row in table on master
> * execute DROP TABLE on pglogical slave
> * commit prepared on master
>
> Now it behaves as expected — slave blocks DROP TABLE until commit prepared
> on master.
>

Try doing DDL in the prepared xact on the upstream side, especially things
that make structural changes to tables. Test both things that do full-table
rewrites (alter table ... add column ... default not null) and things that
don't (alter table ... drop column ; alter table ... add column ...;
without not null or default).

--
Craig Ringer http://www.2ndQuadrant.com/
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