On Thu, Aug 12, 2010 at 12:37 PM, Scott Marlowe
<scott.marlowe@gmail.com> wrote:
On Wed, Aug 11, 2010 at 11:41 PM, Greg Smith <
greg@2ndquadrant.com> wrote:
> Sandeep Srinivasa wrote:
>>
>> Maybe a tabular form would be nice - "work_mem" under...
>
> The problem with work_mem in particular is that the useful range depends
> quite a bit on how complicated you expect the average query running to be.
runs batch processes for one or two import processes and then has
another two or three used to query it can run much higher work_mem
than a machine with 32G set to handle hundreds of concurrent accesses.
Don't forget that when you set work_mem to high it has a very sharp
dropoff in performance as swapping starts to occur. If work_mem is a
little low, queries run 2 or 3 times slower. If it's too high the
machine can grind to a halt.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Right there - could this information not have been captured in the tabular form I was talking about ? Again, I'm not sure how to present the data, but it sure would be of *some* help to the next poor soul who comes along with same question.
This here is golden knowledge - yes you might not be able to add all the qualifiers to just saying ">8GB use X work_mem", but it really, really is much better than nothing that we have now.
-Sandeep