On Wed, 24 Apr 2002, Bruce Momjian wrote:
> We expect the file system to do re-aheads during a sequential scan.
> This will not happen if someone else is also reading buffers from that
> table in another place.
Right. The essential difficulties are, as I see it:
1. Not all systems do readahead.
2. Even systems that do do it cannot always reliably detect that they need to.
3. Even when the read-ahead does occur, you're still doing more syscalls, and thus more expensive kernel/userland
transitions,than you have to.
Has anybody considered writing a storage manager that uses raw
partitions and deals with its own buffer caching? This has the potential
to be a lot more efficient, since the database server knows much more
about its workload than the operating system can guess.
cjs
--
Curt Sampson <cjs@cynic.net> +81 90 7737 2974 http://www.netbsd.org Don't you know, in this new Dark Age, we're
alllight. --XTC
