On Fri, Apr 12, 2013 at 09:28:42PM +0200, Andres Freund wrote: > > Only point worth discussing is that this change would make backup blocks be > > covered by a 16-bit checksum, not the CRC-32 it is now. i.e. the record > > header is covered by a CRC32 but the backup blocks only by 16-bit. > > That means we will have to do the verification for this in > ValidXLogRecord() *not* in RestoreBkpBlock or somesuch. Otherwise we > won't always recognize the end of WAL correctly. > And I am a bit wary of reducing the likelihood of noticing the proper > end-of-recovery by reducing the crc width. > > Why again are we doing this now? Just to reduce the overhead of CRC > computation for full page writes? Or are we forseeing issues with the > page checksums being wrong because of non-zero data in the hole being > zero after the restore from bkp blocks?
I thought the idea is that we were going to re-use the already-computed CRC checksum on the page, and we only have 16-bits of storage for that. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
