Re: weird hang while running in HS mode

On Thu, May 13, 2010 at 3:50 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> rhaas=# rollback;
> ROLLBACK
>
> So at this point, one would think that there are no locks hanging
> around anywhere.  Back to the standby:
>
> rhaas=# select * from pgbench_accounts;
> <really long hang>

I think that this problem happens because the WAL record of ROLLBACK
is not flushed to the disk immediately (i.e., until another transaction
flushes the WAL records in wal_buffers) when we execute the ROLLBACK
command. The walsender sends only the WAL records in the disk, so the
standby server would not be able to replay the ROLLBACK and not release
the lock.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center