On Thu, 2005-03-24 at 10:48 +0100, Patrick Vedrines wrote: > > You've got 1.5Gb of shared_buffers and > 2Gb data. In 8.0, the scan > will > > hardly use the cache at all, nor will it ever, since the data is > bigger > > than the cache. Notably, the scan of B should NOT spoil the cache > for A > Are you sure of that ? Is Postgres able to say to OS: "don't use the > cache for this query"?
PostgreSQL 8.0 has the ARC algorithm which prevents cache spoiling of the shared_buffers, but has no direct influence over the OS cache. > > Priming the cache is quite hard...but not impossible. > > What will kill you on a shared_buffers that big is the bgwriter, > which > > you should turn off by setting bgwriter_maxpages = 0 > Is bgwriter concerned as my application applyes only SELECT ? With very large shared_buffers the bgwriter's default settings are a problem. You don't need it, so I suggest turning it off. Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
