On Fri, 2008-10-17 at 12:26 -0300, Alvaro Herrera wrote: > Apparently the only solution in sight is to WAL-log hint bits. Simon > opines it would be horrible from a performance standpoint to WAL-log > every hint bit set, and I think we all agree with that. So we need to > find an alternative mechanism to WAL log hint bits.
Yes, it's clearly not acceptable bit by bit. But perhaps writing a single WAL record if you scan whole page and set all bits at once. Then it makes sense in some cases. It might be possible to have a partial solution where some blocks have CRC checks, some not. Most databases have static portions. Any block not touched for X amount of time (~= to a distance between current LSN and LSN on block) could have CRC checks added. Or maybe just make it a table-level option and let users choose if they want the hit or not. Or maybe have a new command that you can run whenever you want to set CRC checks. That way you get to choose. CHECK TABLE? -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
