Re: Online enabling of checksums

> The change of the checksum state is WAL logged with a new xlog record. All the buffers written by the background
workerare forcibly enabled full page writes to make sure the checksum is fully updated on the standby even if no actual
contentsof the buffer changed. 

Hm. That doesn't sound necessary to me. If you generate a checkpoint
(or just wait until a new checkpoint has started) then go through and
do a normal xlog record for every page (any xlog record, a noop record
even) then the normal logic for full page writes ought to be
sufficient. If the noop record doesn't need a full page write it's
because someone else has already come in and done one and that one
will set the checksum. In fact if any page has an lsn > the checkpoint
start lsn for the checkpoint after the flag was flipped then you
wouldn't need to issue any record at all.