Re: tracking commit timestamps

On Thu, Dec 4, 2014 at 12:58 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On 4 December 2014 at 03:08, Fujii Masao <masao.fujii@gmail.com> wrote:
>
>> #1. set up and start the master and standby servers with
>> track_commit_timestamp disabled
>> #2. enable track_commit_timestamp in the master and restart the master
>> #3. run some write transactions
>> #4. enable track_commit_timestamp in the standby and restart the standby
>> #5. execute "select pg_xact_commit_timestamp('1000'::xid)" in the standby
>
> I'm not sure what step4 is supposed to do?
>
> Surely if steps 1-3 generate any WAL then the standby should replay
> it, whether or not track_commit_timestamp is enabled.
>
> So what effect does setting that parameter on the standby?

At least track_commit_timestamp seems to need to be enabled even in the standby
when we want to call pg_xact_commit_timestamp() and pg_last_committed_xact()
in the standby. I'm not sure if this is good design, though.

Regards,

-- 
Fujii Masao