On Wed, Mar 13, 2019 at 12:24:21PM +0100, Magnus Hagander wrote: > Enabling or disabling the checksums offline on the master quite clearly > requires a rebuild of the standby, there is no other way (this is one of > the reasons for the online enabling in that patch, so I still hope we can > get that done -- but not for this version).
I am curious to understand why this would require a rebuild of the standby. Technically FPWs don't update the checksum of a page when it is WAL-logged, so even if a primary and a standby don't agree on the checksum configuration, it is the timing where pages are flushed in the local instance which counts for checksum correctness. > You mean if the backend and pg_checksums is built with different blocksize? > Yeah, that sounds like something which is a cheap check and should be done. Yes, we should check after that, checksum calculation uses BLCKSZ with a hardcoded value, so a mismatch would cause computation failures. It could be possible to not have this restriction if we made the block size an argument of the checksum calculation though. -- Michael
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