On 7 May 2014 13:31, Robert Haas <robertmh...@gmail.com> wrote: > On Wed, May 7, 2014 at 3:18 AM, Simon Riggs <si...@2ndquadrant.com> wrote: >> If we believe that 25% of shared_buffers worth of heap blocks would >> flush the cache doing a SeqScan, why should we allow 400% of >> shared_buffers worth of index blocks? > > I think you're comparing apples and oranges.
I understood the distinction, which is why I changed the direction of my thinking to say > Yes, we can make plans assuming we can use OS cache, > but we shouldn't be churning shared_buffers when we execute those > plans. and hence why I proposed > I think I'm arguing myself towards using a BufferAccessStrategy of > BAS_BULKREAD for large IndexScans, BitMapIndexScans and > BitMapHeapScans. which I hope will be effective in avoiding churn in shared_buffers even though we may use much larger memory from the OS. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers