On Tue, 13 Nov 2007, Andrew Sullivan wrote:
I have to agree with what Tom says, however, about people thinking they're smarter than the system. Much of the time, this sort of thumb on the scale optimisation just moves the cost to some other place
Sure, but in this case the reasoning seems sound enough. The buffer eviction policy presumes that all buffers cost an equal amount to read back in again. Here we have an application where it's believed that's not true: the data on disk for this particular table has a large seek component to it for some reason, it tends to get read in large chunks (but not necessairly frequently), and latency on that read is critical to business requirements. "The system" doesn't know that, and it's impractical to make it smart enough to figure it out on its own, so asking how to force that is reasonable.
I see this as similar to the old optimizer hint argument, where there certainly exist some edge cases where people know something the optimizer doesn't which changes the optimal behavior.
-- * Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
