Re: How to keep a table in memory?

On Tue, 2007-11-13 at 14:36 -0500, Greg Smith wrote:
> 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.

It seems possible to imagine a different buffer eviction policy based
upon tablespace, block type, peak rather than latest usage pattern etc..

--  Simon Riggs 2ndQuadrant  http://www.2ndQuadrant.com