On Wed, Mar 1, 2017 at 6:02 AM, Sven R. Kunze <srkunze@xxxxxxx> wrote:
On 28.02.2017 17:49, Jeff Janes wrote:
Oh. In my hands, it works very well. I get 70 seconds to do the {age: 20} query from pure cold caches, versus 1.4 seconds from cold caches which was followed by pg_prewarm('docs','prefetch').
How much RAM do you have? Maybe you don't have enough to hold the table in RAM. What kind of IO system? And what OS?
On my test system:
RAM: 4GB
IO: SSD (random_page_cost = 1.0)
OS: Ubuntu 16.04
4GB is not much RAM to be trying to pre-warm this amount of data into. Towards the end of the pg_prewarm, it is probably evicting data read in by the earlier part of it.
What is shared_buffers?
Cheers,
Jeff
