Re: pg_rewind exiting with error code 1 when source and target are on the same timeline

On Thu, Oct 22, 2015 at 7:42 AM, Michael Paquier
<michael.paquier@gmail.com> wrote:
> On Thu, Oct 22, 2015 at 4:08 AM, Peter Eisentraut <peter_e@gmx.net> wrote:
>> I agree that that should not be an error.
>> But I think in that case we should just delete that check and have the
>> subsequent checks end up at the existing "no rewind required" result.
> I am not sure that I am not getting completely your point, why would
> it be a win to remove this safety check? We surely do not want to look
> for the common ancestor timeline if the target and source nodes have
> the same timeline, so we should not remove this check and just set
> rewind_needed to false to fallback to the same exit(0) for all those
> code paths. Per se the attached for example.

I'm not familiar with pg_rewind, but from a programming perspective I
agree with Peter. If you will end with a no-rewind-required result
when not checking for equality the same timeline check is not a safety
check, but an optimisation. Then removing it can make sense, as
deleted code cannot contain bugs. If searching for the common ancestor
can lead to problems then its a safety check.

Francisco Olarte.