Re: Patch for fail-back without fresh backup

On Thu, Sep 19, 2013 at 7:07 PM, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Thu, Sep 19, 2013 at 12:25 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>> On Thu, Sep 19, 2013 at 11:48 AM, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>> I attached the patch which I have modified.
>>
>> Thanks for updating the patch!
>>
>> Here are the review comments:
>>
>
> Thank you for reviewing!
>
>> I got the compiler warning:
>>
>> syncrep.c:112: warning: unused variable 'i'
>>
>> How does synchronous_transfer work with synchronous_commit?
>
> The currently patch synchronous_transfer doesn't work when
> synchronous_commit is set 'off' or 'local'.
> if user changes synchronous_commit value on transaction, checkpointer
> process can't see it.
> Due to that, even if synchronous_commit is changed to 'off' from 'on',
> synchronous_transfer doesn't work.
> I'm planning to modify the patch so that synchronous_transfer is not
> affected by synchronous_commit.

Hmm... when synchronous_transfer is set to data_flush,
IMO the intuitive behaviors are

(1) synchronous_commit = on
A data flush should wait for the corresponding WAL to be
flushed in the standby

(2) synchronous_commit = remote_write
A data flush should wait for the corresponding WAL to be
written to OS in the standby.

(3) synchronous_commit = local
(4) synchronous_commit = off
A data flush should wait for the corresponding WAL to be
written locally in the master.

Regards,

--
Fujii Masao