Re: Online enabling of checksums

On Sun, Feb 25, 2018 at 9:54 AM, Magnus Hagander <magnus@hagander.net> wrote:
> Also if that wasn't clear -- we only do the full page write if there isn't
> already a checksum on the page and that checksum is correct.

Hmm.

Suppose that on the master there is a checksum on the page and that
checksum is correct, but on the standby the page contents differ in
some way that we don't always WAL-log, like as to hint bits, and there
the checksum is incorrect.  Then you'll enable checksums when the
standby still has some pages without valid checksums, and disaster
will ensue.

I think this could be hard to prevent if checksums are turned on and
off multiple times.

-- 
Robert Haas
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