On Thu, Nov 28, 2013 at 9:42 PM, Sawada Masahiko <sawada.m...@gmail.com> wrote: > I attached new version patch which have modify typos and added > documentation patch. > The documentation part of patch is implemented by Samrat Revagade. Thanks for the new version. The documentation still has some typo: - is ,<literal>off</> => is <literal>off</>
I have been pondering about this feature over the weekend and I have to admit that the approach using a GUC that can be modified after server initialization is not suited. What we want with this feature is to be able to include hint bits in WAL to perform WAL differential operations which is in some way what for example pg_rewing is doing by analyzing the relation blocks modified since the WAL fork point of a master with one of its promoted slave. But if this parameter can be modified by user at will, a given server could finish with a set of WAL files having inconsistent hint bit data (some files might have the hint bits, others not), which could create corrupted data when they are replayed in recovery. Considering that, it would make more sense to have this option settable with initdb only and not changeable after initialization, in the same fashion as checksums. Having a GUC that can be used to check if this option is set or not using a SQL command could be an additional patch on top of the core feature. This does not mean of course that this patch has to be completely reworked as the core part of the patch, the documentation and the control file part would remain more or less the same. Regards, -- Michael -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers