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 (pgsql-hackers@postgresql.org)
To make changes to your subscription:

Reply via email to