Re: WAL replay bugs

On Tue, Jun 17, 2014 at 5:40 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> 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.

No, I was trying to get it down form 2 servers to 1, not 2 servers up to 3.

>> 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.

Cool!

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company