Re: WAL consistency check facility

On Sun, Sep 11, 2016 at 12:03 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> It seems entirely unnecessary for the master and the standby to agree
> here. I think what we need is two GUCs. One of them, which affects
> only the master, controls whether the validation information is
> including in the WAL, and the other, which affects only the standby,
> affects whether validation is performed when the necessary information
> is present. Or maybe skip the second one and just decree that
> standbys will always validate if the necessary information is present.
> Using the same GUC on both the master and the standby but making it
> mean different things in each of those places (whether to log the
> validation info in one case, whether to perform validation in the
> other case) is another option that also avoids needing to enforce that
> the setting is the same in both places, but probably an inferior one.

Thinking more about that, there is no actual need to do anything
complicated here. We could just track at the record level if a
consistency check is needs to be done at replay and do it. If nothing
is set, just do nothing. That would allow us to promote this parameter
to SIGHUP. wal_compression does something similar.
--
Michael