On Tue, 2008-09-30 at 17:13 -0400, [EMAIL PROTECTED] wrote: > > > > I believe the idea was to make this as non-invasive as possible. And > > it would be really nice if this could be enabled without a dump/ > > reload (maybe the upgrade stuff would make this possible?) > > -- > > It's all about the probability of a duplicate check being generated. If > you use a 32 bit checksum, then you have a theoretical probability of 1 in > 4 billion that a corrupt block will be missed (probably much lower > depending on your algorithm). If you use a short, then a 1 in 65 thousand > probability. If you use an 8 bit number, then 1 in 256. > > Why am I going on? Well, if there are any spare bits in a block header, > they could be used for the check value.
Even and 64-bit integer is just 0.1% of 8k page size, and it is even less than 0.1% likely that page will be 100% full and thus that 64bits wastes any real space at all. So I don't think that this is a space issue. --------------- Hannu -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
