On Wed, Jun 18, 2003 at 10:01:37AM +1000, Gavin Sherry wrote: > On Tue, 17 Jun 2003, Tom Lane wrote: > > * Consider use of open/fcntl(O_DIRECT) to minimize OS caching > > > > I personally disagree with this TODO item for the same reason Sean > > cited: Postgres is designed and tuned to rely on OS-level disk caching, > > and bypassing that cache is far more likely to hurt our performance than > > help it. > > DB2 and Oracle, from memory, allow users to pass hints to the planner to > use/not use file system caching. This could be useful if you had an > application retrieving a large amount of data on an adhoc basis. The large > retrieval would empty out the disk cache there by negatively impacting > upon other applications operating on data which should be cached. Might it make sense to do this for on-disk sorts, since sort_mem is essentially being used as a disk cache (at least for reads)? -- Jim C. Nasby (aka Decibel!) [EMAIL PROTECTED] Member: Triangle Fraternity, Sports Car Club of America Give your computer some brain candy! www.distributed.net Team #1828
Windows: "Where do you want to go today?" Linux: "Where do you want to go tomorrow?" FreeBSD: "Are you guys coming, or what?" ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
