Re: turn off caching for performance test

On Thu, Aug 26, 2010 at 4:32 AM, Willy-Bas Loos  wrote:
> Hi,
>
> I have a colleague that is convinced that the website is faster if
> enable_seqscan is turned OFF.
> I'm convinced of the opposite (better to leave it ON), but i would like to
> show it, prove it to him.

Stop, you're both doing it wrong.  The issue isn't whether or not
turning off seq scans will make a few things faster here and there,
it's why is the query planner choosing sequential scans when it should
be choosing index scans.

So, what are your non-default settings in postgresql.conf?
Have you increased effective_cache_size yet?
Lowered random_page_cost?
Raised default stats target and re-analyzed?

Have you been looking at the problem queries with explain analyze?
What does it have to say about the planners choices?