Re: WAL replay bugs

On Wed, Jun 18, 2014 at 1:40 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Jun 2, 2014 at 8:55 AM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
> I'm not sure if this is reasonably possible, but one thing that would
> make this tool a whole lot easier to use would be if you could make
> all the magic happen in a single server. For example, suppose you had
> a background process that somehow got access to the pre and post
> images for every buffer change, and the associated WAL record, and
> tried applying the WAL record to the pre-image to see whether it got
> the corresponding post-image. Then you could run 'make check' or so
> and afterwards do something like psql -c 'SELECT * FROM
> wal_replay_problems()' and hopefully get no rows back.
So your point is to have a 3rd independent server in the process that
would compare images taken from a master and its standby? Seems to
complicate the machinery.

> Don't get me wrong, having this tool at all sounds great. But I think
> to really get the full benefit out of it we need to be able to run it
> in the buildfarm, so that if people break stuff it gets noticed
> quickly.
The patch I sent has included a regression test suite making the tests
rather facilitated: that's only a matter of running actually "make
check" in the contrib repository containing the binary able to compare
buffer captures between a master and a standby.

Thanks,
--
Michael